Muhammad Altaf Nazir*a,
Sami Ullaha,
Asif Jamilb,
Ibrahim A. Shaabanc,
Lala Gurbanovad,
Karim Khanef,
Syed Shoaib Ahmad Shah
*g and
Shu-Juan Bao
*hi
aInstitute of Chemistry, The Islamia University of Bahawalpur, Bahawalpur 63100, Pakistan. E-mail: altaf.nazir@iub.edu.pk
bDepartment of Mechanical Engineering, Kaunas University of Technology, Studentug.56, Kaunas 51424, Lithuania
cChemistry Department, Faculty of Science, Research Center for Advanced Materials Science (RCAMS), King Khalid University, Abha, Saudi Arabia
dDepartment of Life Sciences, Western Caspian University, Baku, Azerbaijan
eAdditive Manufacturing Institute, Shenzhen University, Shenzhen, 518060, China
fSchool of Mathematical and Physical Sciences, University of Technology, Sydney, Australia
gDepartment of Chemistry, School of Natural Sciences, National University of Sciences and Technology, Islamabad 44000, Pakistan. E-mail: shoaib03ahmad@outlook.com
hSchool of Materials and Energy, Southwest University, Chongqing 400715, P. R. China. E-mail: baoshj@swu.edu.cn
iChongqing Key Lab for Battery Materials and Technologies, Southwest University, Chongqing 400715, P. R. China
First published on 10th July 2025
Owing to the characteristics of metal–organic frameworks (MOFs) and their variants, such as large specific surface area, high porosity, tunable structure, and ease of structural modulation, MOFs have been extensively used as electrode materials, separators, electrocatalysts, and other components of energy storage systems. Nevertheless, there are several practical issues associated with the use of MOFs that have not yet been fully resolved. The current research progress in incorporating MOFs and their derived materials into energy storage devices, including alkali-metal-ion batteries, metal sulphur batteries, aqueous zinc-ion batteries, and supercapacitors, is presented in this paper. It also provides design solutions to some major problems, such as dendrite growth and shuttle effects, which are almost always observed in secondary batteries. In addition, the design ideas for MOF-derived carbon material heterostructures and metal compound structure modification are summarized. This review provides a comprehensive compilation of the most recent studies in the domain of energy storage and conversion. Finally, the intrinsic regulation of MOF precursors and modification strategies of the materials are summarized and prospected.
Metal–organic frameworks (MOFs) are used to describe coordination polymers (o-CPs) connected by metals and organic ligands.9–11 Typically, MOFs are crystalline substances composed of organic ligands and metal nodes. The metal nodes can be ions of alkali metals, transition metals or lanthanide elements. Typically, organic ligands are based on phosphates, carboxylates, and N-donor groups.12–14 This type of material is completely regular in morphology and has the characteristics of high porosity and controllable structure15–17 and broad application prospects in gas storage, catalysis, chemical sensing and other fields.18–20 The earliest research on MOF materials can be traced back to MOF-5 and the subsequent zeolite imidazole framework (ZIF) series proposed by Li et al.,21 who verified their permanent porosity and high thermal stability,22 laying a solid foundation for the preparation and application of subsequent MOF derivative materials. In the subsequent research on MOF materials, different types of MOFs were developed for application in various fields according to different metal nodes or organic ligands, including IRMOF-1, IRMOF-3 (mostly used for gas selective capture),23,24 ZIF (common ones include ZIF-8, ZIF-9, and ZIF-67),25,26 MIL (mostly composed of high-valent metal cations such as Fe3+, V3+, and Al3+) and organic ligands such as 1,3,5-benzenetricarboxylic acid (BTC) or 1,4-benzenedicarboxylic acid (BDC),27 porous coordination networks (PCNs), University of Oslo (UIO) and other series. The synthesis of MOF materials generally follows the following methods: solvothermal, electrochemical, direct precipitation, microwave promotion, mechanochemical, ultrasound-assisted and self-assembly methods.28 In 2017, Rubio-Martinez et al. reviewed the synthesis schemes for MOFs from laboratory to industrialization and believed that solvent-free and aqueous phase synthesis methods are most likely to become large-scale production strategies.29 In the last several years, new and diverse types of MOF structures and their associated materials have attracted great interest in energy storage applications. The primary area of study for MOFs and their derived materials is the development of appropriate preparation techniques and performance control mechanisms.
Several research has been conducted recently to assess the potential of MOF-based materials for energy storage. Liang et al. examined and assessed the development of MOFs in lithium–oxygen and lithium-ion batteries, lithium–sulfur batteries, and supercapacitors, but derelict to cover additional alkali-metal-ion batteries.30 Despite Wang et al.'s comprehensive review of MOF applications and related composite materials, there are currently no practical guidelines for MOF material structural design.31 This article provides a complete review of the use of MOF materials in supercapacitors and secondary batteries, as well as an investigation of the structural design and modification strategies of MOF derivative materials. This review aims to provide readers with a more thorough grasp of how MOFs are used in energy storage and to assist them in creating MOF materials with improved electrochemical performance. The diagrammatic depiction of the review outline is shown in Fig. 1.
The porous structure of MOFs expands the area of contact between active materials and electrolytes, which accelerates lithium-ion diffusion and improves lithium-ion battery performance. It has consequently demonstrated the significant potential of lithium-ion batteries as electrode materials.28,51,52 As an anode material for a lithium-ion battery, Lin et al. used a solvothermal technique to generate a cadmium-based metal–organic framework (Cd-MOF) with remarkable thermal stability. They calcined it at 800 °C while nitrogen was present, producing nitrogen-doped carbon material NC800.53 The electrode had a remarkable cycle life, with a specific capacity of 741 mAh g−1 after 100 cycles at a current density of 100 mA g−1. The abundance of microtube structures in nitrogen-doped carbon-based materials, which serve as reservoirs for Li+ storage, is responsible for their exceptional cycle stability and capacity. Furthermore, the amount of nitrogen-rich composition enhances the lithium storage capacity to a certain degree. In recent years, significant effort has been made to incorporate favorable altered MOFs into the negative electrode materials of lithium-ion batteries via multimetal doping. The synthesis of bimetallic MOFs can enhance their electrochemical performance54 because multi-component metal nodes can expose more reactive sites, and the obvious advantages of kinetics and thermodynamics can form a synergistic effect; thus, these materials have shown considerable prospects when applied to lithium-ion battery anode materials. The bimetallic compound [Ir(ppy-COO)3] has the formula Co4(μ4-O). Yan et al. created 2MOF (Co4-IrMOF), as a high-efficiency lithium-ion storage anode material (Fig. 3a).55 This MOF, composed of Ir(ppy-COOH)3 ligands and Co4(μ4-O) clusters, coordinates around the spacer, showing a Li-ion diffusion coefficient being 2 × 10−2 A g−1, higher than that of graphite and an electrical conductivity 4× higher than that of the insulating MOFs, increasing rate capabilities in the process. Co4–Ir MOF's organized porous framework and laminated stacking structure guarantee quick Li+ transfer and storage with minimal volume change. At 3000 mA, it also shows great rate capability and a specific capacity of 515 mAh g−1 (Fig. 3b and c). Fig. 3d–f shows the long-term stability and charge–discharge curves. Fig. 3g shows the Co4–Ir MOF‖NCM523's long-term cycling stability. Metal selenides are further prepared using multi-metal materials as precursors. The higher polarization of selenium can theoretically lead to better rate performance, whereas nitrogen-doped carbon can improve conductivity. Zhang et al. suggested an aqueous-phase approach with KOH assistance to prepare many bimetallic MOF compounds.56 They produced a 3D polyhedral Fe–Co–Se/NC with a fully porous structure. When evaluated as a lithium-ion battery's anode material, in the first cycle, this lithium-ion negative electrode has a discharge-specific capacity of 1165.9 mAh g−1 at 1.0 A g−1. After 550 cycles, the reversible capacity had reached 1247.4 mAh g−1. The stable 3D structure of Fe–Co–Se/NCs ensures the structural stability and wettability of the electrolyte, the uniform distribution of Fe–Co–S nanoparticles in size suppresses volume expansion and speeds up the kinetics of electrochemical reactions, and the uniform composite of bimetallic selenides and N-doped carbon is responsible for the efficient tuning of redox active sites.
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Fig. 3 (a) Co4–Ir MOF synthesis and structure representation; (b) Co(II) ion coordination environment in Co4(μ4-O) cluster; (c) HLIC CV curves; (d) charge–discharge curves of HLICs; (e) stability of HLICs at 4000 mA g−1 current density; (f) current density galvanostatic charge–discharge plots and the continuous unbending function for soft packed battery; (g) Co4–Ir MOF‖NCM523 complete cell cycling stability. Reproduced with permission from ref. 55, Copyright 2021 Wiley. |
Recently, Dai et al. synthesized the bimetallic MOF material nickel-iron(III)-coordinated 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin (TCPP(Fe)-Ni) via a solvothermal technique (Fig. 4a).57 Organic ligands derived from metalloporphyrin further improve the Li+ intercalation that the TCPP(Fe)-Ni anode has in terms of Li+ ion and electron transport rate. In comparison to the Ni-TCPP MOF, which shows 560 mAh g−1 after earlier 50 cycles at 0.1 A g−1, the TCPP(Fe)-Ni anode records significantly greater lithium storage and a roughly 950 mAh g−1 reversible capacity after 50 cycles at 0.1 A g−1, as indicated in Fig. 4b–f. When used as a negative electrode for lithium-ion batteries, it showed excellent rate capability and a high reversible capacity of 950 mAh g−1 at 0.1 A g−1. Yin et al. designed a one-pot procedure to synthesize a new 2D c-MOF named Cu3(HHTP)(THQ) (HHTP = 2,3,6,7,10,11-hexahydroxytriphenyl, THQ = tetrahydroxy-1,4-benzoquinone) using a dual-ligand system. Using ethylenediamine to modulate the competing coordination between HHTP and THQ ligands, this method provides a basis for synthesizing two-dimensional dual-ligand c-MOFs.58 In another study, Cu3(HHTP)(THQ) was synthesized as an anode material for lithium-ion batteries, possessing great stability, a large number of active sites, and exceptional electrical conductivity. This anode material exhibits a Coulomb efficiency of 57.9%, an initial discharge capacity of 1218.9 mAh g−1, and an initial charge capacity of 705.4 mAh g−1. The Cu3(HHTP)(THQ) electrode with a porous structure has a decreased initial coulombic efficiency due to electrolyte degradation and the production of SEI films on its active material surface.59 This can be resolved by prelithiating the electrode using additives that generate SEI and by adjusting the electrolyte composition.60 In the second, third, fourth, and fifth cycles, Cu3(HHTP)(THQ) had discharge/charge capacities of 734.7/686.5, 734.1/695.2, 725.1/695.7 and 726.0/699.6 mAh g−1 respectively as well as coulombic efficiencies of 93.4%, 94.7%, and 95.5%. Furthermore, the cyclic performance was investigated at 300 mA g−1 to understand its overall long-term cycling behavior. The specific capacity decreased during the first cycle and subsequently increased dramatically, perhaps due to incorrect electrolyte penetration and electrode activation. Table 1 presents the performance of MOFs as advanced materials for lithium-ion battery applications.
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Fig. 4 (a) Illustration of TCPP(Fe)-Ni MOF synthesis; (b) CV curves at a rate of 0.1 mV s−1; (c) 200 voltage–capacity curves at the starting point at 1.0 A g−1; (d) rate performance; (e) CV curves for TCPP(Fe)-Ni at 0.1–1.5 mV s−1; (f) cyclic performance of TCPP(Fe)-Ni and Ni-TCPP at 1.0 A g−1. Reproduced with permission from ref. 57, Copyright 2023 American Chemical Society. |
Pristine MOFs | Application | Cycle number | Specific capacity (mA g−1) | Current density (mA g−1) | Ref. |
---|---|---|---|---|---|
Ni-MOF | LIBs | 100 | 620 | 100 | 61 |
Fe-BTC | LIBs | 100 | 1021 | 100 | 62 |
Pb-MOF | LIBs | 500 | 489 | 100 | 63 |
Mn-BTC | LIBs | 100 | 694 | 103 | 64 |
Ti-MOF | LIBs | 50 | 527.12 | 100 | 65 |
MIL-53 | LIBs | 50 | 71 | 0.2C | 66 |
NCM-622 | LIBs | 100 | 214.6 | 0.2C | 67 |
MIL-68 | LIBs | 12 | 32 | 0.2C | 68 |
Fe-MIL-88B | LIBs | 400 | 744.5 | 60 | 69 |
MIL-47 | LIBs | 50 | 70 | 10 | 70 |
Ni-Zn-BTC | LIBs | 200 | 1297.2 | — | 71 |
Mn-BTC | LIBs | 100 | 103 | — | 72 |
Mn-1,4-BDC | LIBs | 100 | 100 | — | 73 |
Co(L) MOF/RGO | LIBs | 50 | 1185 | 100 | 74 |
MOF-177 | LIBs | 2 | 425 | 50 | 75 |
Zn3(HCOO)6 | LIBs | 60 | 1344 | 60 | 76 |
Zn-MOF-Crown | LIBs | 500 | 271 | 500 | 77 |
Zn-BPC | LIBs | 100 | 816.3 | 100 | 78 |
BMOFs | LIBs | 100 | 190 | 100 | 79 |
MOF-5 | LIBs | 100 | 1982 | 100 | 80 |
EEG-ZIF-8 | LIBs | 100 | 1400 | 97.8 | 81 |
Cu3(BTC)2 | LIBs | 50 | 383 | 96 | 82 |
MOF-5 | LIBs | 100 | 1564.8 | 100 | 83 |
ZIF-8@CNTs | LIBs | 200 | 1300 | 100 | 84 |
MOFs and their derivatives are excellent choices for lithium-ion battery electrode materials. Techniques for doping multi-metal components and synthesizing the correspondingly improved metal-based composites have enabled the further incorporation of MOF-based composites for application in the negative electrodes of lithium-ion batteries.
Recently, lots of work has focused on carbon-type materials, including graphite, heteroatom-doped carbon, amorphous carbon and carbon derived from biomass, to enhance the performance of energy storage.90 According to this idea, carbon compounds produced from MOFs can enhance conductivity while preserving their high-porosity structure, making it possible to create negative-electrode sodium-ion battery materials with superior performance. Heteroatom doping in porous carbon materials was suggested by Cui et al. as a way to enhance salt-storage capabilities.91 Based on the idea that metal phosphides and heteroatom-doped carbon materials are great for storing sodium, Zhao et al.92 recently combined red phosphorus and ZIF-67 and then calcined them in a protective environment to create a nitrogen-doped cobalt phosphide carbon composite material CO2P at NC-12.5. The high diffusion coefficient and reduced interface impedance at the electrode interface were validated by GITT and EIS. Co2P@NC offers quick electron transfer and viable active sites for sodium-ion batteries due to its short sodium-ion diffusion path and good structural integrity. After using the material as a negative electrode in sodium-ion batteries, the application exhibited a reversed capacity of more than 350 mAh g−1 at a current density of 0.1 A g−1. Feng et al. used the ideas of nitrogen doping, carbon skeletons, and metal selenides to generate CoSe@NC/MoSe2 bimetallic selenide composite materials.93 Although the nitrogen-doped carbon matrix guarantees sodium-ion transport capability, this multi-component composite approach enhances the sodium storage performance. Furthermore, the porous structure ensures exceptional structural stability during cycling and offers a low Na+ diffusion distance. The discharge capacity of the sodium particle cathode material is 305.9 mAh g−1 at a current density of 5.0 A g−1. With enough graphite-induced conditions, Li et al. grew graphite-like crystals, a novel carbon allotrope.94 Under graphite induction, they could successfully grow and construct Zn-TDPAT MOF-derived crystalline carbon by regulating the reaction inflection temperature. At the point when used as a sodium particle-negative cathode, the Zn-TDPAT-GC terminal exhibited predominant electrochemical execution and great stability. After 50 charge–discharge cycles at a current density of 20 mA g−1, the reversible capacity of LVO reached 354 mAh g−1, which was equal to 97.5% of the original capacity.
Morphological engineering techniques such as sandwich structure design, hollow structures, and amorphous phosphate have been successfully developed to improve the performance of SIBs and anode quality. For rapid sodium-ion storage, Zhao et al. developed cubic Co2P@NC produced from MOFs (Fig. 5a) and used it as a quick anode.95 Co2P@NC anodes have low interfacial impedance and a high diffusion coefficient, allowing for rapid electron passage. The discharge profiles of Co2P@NC-12.5 anodes show significant reversible capacity (Fig. 5b and c). A new MOF-engaged synthesis strategy for CoSe@NC/MoSe2 polyhedrons was recently developed by Feng et al. (Fig. 5d).96 The N-doped carbon framework and porous structure can minimize serious agglomeration and alleviate structural strain through multiple cycles. The composite exhibits high cyclability (305.9 mAh g−1 up to 1500 loops at 5.0 A g−1) and rate capability (286.1 mAh g−1 at 10.0 A g−1) for salt deposition. Synchronizing the Na3V2(PO4)3@C cathode with an SIB full cell resulted in a high invertible capacity of 78.9 mAh g−1 with 100 loops at 0.5 A g−1. The binary metal selenides exhibit remarkable cycle stability and rate capability in SIB half/full cells (Fig. 5e–j).
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Fig. 5 (a) Co2P@NC nanocube synthesis process diagram; (b) CV curves of Co2P@NC-12.5; (c) charge/discharge patterns of Co2P@NC-12.5 at 0.1 A g−1. Reproduced with permission from ref. 95, Copyright 2023 Elsevier. (d) Diagrammatic representation of the composite production process and SIBs' electrochemical activity; (e) CV profiles of the CoSe@NC/MoSe2 electrode; (f) discharge and charge voltage patterns at 0.2 A g−1; (g) Na3V2(PO4)3@C//CoSe@NC/MoSe2 whole-cell electrochemical testing performance at 0.2 A g−1; (h) diagrammatic representation of the SIB complete cell; (i) charge/discharge curves for the first three cycles; (j) the SIB complete cell's rate capability at a 0.5–3.0 V cut-off voltage. Reproduced with permission from ref. 96, Copyright 2023 Elsevier. |
Lately, research into improving the performance of sodium-ion battery electrode materials has extensively used the ideas of defect introduction and heteroatom doping. Yao et al.97 doped MIL-125 using the solvothermal method, and then they prepared Si–TiO2-x@C material with Si atom doping and oxygen vacancy defects by annealing and NaOH etching. The prepared material served as the SIB anode. The presence of oxygen vacancy defects verified by EPR enhanced the conductivity and reaction kinetics. The Si–TiO2-x@C showed good long-term cycling, high-rate performance (190 mAh g−1 at 2 A g−1 after 2500 cycles with 95.1% capacity retention), and a high sodium storage capacity (285 mAh g−1 at 0.2 A g−1). According to theoretical estimates, Si doping and abundant Ti3+/oxygen vacancies work together to reduce the sodiation barrier and narrow the bandgap, resulting in fast electron/ion transfer coefficients and the majority of pseudocapacitive sodium storage behavior. Feng et al.98 prepared MIL-101(Al)-NH2MOF as a precursor and then mixed it with sulfur and calcined it to obtain a nitrogen/sulfur binary-doped microporous carbon material, NSPC, as a substance for the negative electrode of sodium-ion batteries. Due to the coating effect of sulfur in the micropores, the internal defects of the micropores were reduced, thereby improving the Initial Coulomb Efficiency (ICE). Dual heteroatom doping had a synergistic effect that increased the diffusion rate of sodium ions, as demonstrated by DFT calculations that revealed that the surface adsorption energy of sodium ions on nitrogen/sulfur dual-doped carbon materials was significantly higher than that on nitrogen-doped materials (−0.5 eV increased to −2.07 eV). Table 2 presents the performance of MOFs as advanced materials for sodium-ion battery applications.
Pristine MOFs | Application | Cycle number | Specific capacity (mAh g−1) | Current density (A g−1) | Ref. |
---|---|---|---|---|---|
Co(L) MOF/RGO | SIBs | 330 | 206 | — | 74 |
Sn-MOF | SIBs | 100 | 970 mAh cm−3 | — | 99 |
MIL-125(Ti)-Co | SIBs | 500 | 140 | 0.5 | 100 |
MIL-125(Ti) | SIBs | 2500 | 173 | 1.0 | 101 |
Co-Zn-ZIF | SIBs | 1000 | 242 | 2.0 | 102 |
Cu-BTC | SIBs | 400 | 212 | 1.0 | 103 |
Cu-BTC | SIBs | 600 | 165 | 2.0 | 103 |
HMT-based MOFs | SIBs | 500 | 145 | 2.0 | 104 |
HMT-based MOFs | SIBs | 500 | 123 | 5.0 | 104 |
HMT-based MOFs | SIBs | 500 | 95 | 10.0 | 104 |
Al-MOF | SIBs | 200 | 210 | 0.1 | 105 |
Mn-MOF | SIBs | 100 | 313.8 | 0.1 | 106 |
MOF-5 | SIBs | 500 | 173.7 | 0.2 | 107 |
MOF-5 | SIBs | 5000 | 100 | 3.2 | 108 |
ZIF-67 | SIBs | 500 | 182 | 0.5 | 109 |
ZIF-8 | SIBs | 2000 | 175 | 1.67 | 110 |
V-MOF nanorods | SIBs | 2000 | 152 | 0.5 | 111 |
V-MOF nanorods | SIBs | 2000 | 123 | 0.1 | 111 |
MIL-125(Ti) | SIBs | 10![]() |
120 | 5.0 | 112 |
Ni-BTC-MOF | SIBs | 300 | 356.2 | 0.5 | 113 |
ZIF-67 | SIBs | 250 | 421 | 2 | 114 |
MIL-88 micro rods | SIBs | 100 | 587 | 0.2 | 115 |
ZIF-67 | SIBs | 1000 | 100 | 1.0 | 116 |
Co-BTC MOF | SIBs | 900 | 386 | 1.0 | 117 |
MIL-88Fe | SIBs | 150 | 449 | 0.5 | 118 |
MOF-derived carbon materials, metal compounds, and multicomponent-doped composite materials combine their respective advantages and exhibit excellent electrochemical performance in sodium-ion batteries. Metal compounds improve sodium storage performance, and heteroatom doping (Si, N, S, etc.) and defect regulation effectively enhance reaction kinetics. The quick development of MOFs as substances for negative sodium-ion battery electrodes is facilitated by these altered design techniques.
Xiao et al. used electrostatic contact and synergistic coordination between graphene oxide (GO) and Co-MOF to grow Co-MOF nanocrystals evenly anchored on graphene oxide to solve the problems of electrode materials' limited capacity and subpar cycle performance.122 Following further annealing, a hybrid material composed of Co-MOF nanocrystals firmly embedded in a reduced graphene oxide network was formed (Fig. 6a). When employed as the PIB negative electrode material, the three-dimensional graphene produced to integrate Co-MOF nanocrystals (Co-MOF-rGO) displayed an increased reversible specific capacitance of 422 mAh g−1 and current density of 0.1 A g−1. The existence of the three-dimensional graphene network increased the total capacitance of the Co-MOF nanocrystals. Fig. 6b shows the discharge and charge graphs of the hybrid anode at different current densities. For example, when the current density was increased to 5 A g−1, Co-MOF-rGO gave a discharge-specific capacity of 202 mAh g−1, showing its superior rate capability. Fig. 6c and d show an anode comparison and cycling performance of the hybrid material and Co-MOF/rGO anode electrodes. When evaluated at 2 A g−1 for 2000 cycles, the power density decreased to 0.013% because of an increased degradation rate. Over the following 2000 cycles, the hybrid anode operates at 2 A g−1, and the CV curves in Fig. 6e and f appear as the scan rate increases. MOFs based on bismuth have been extensively used in recent studies on negative potassium-ion battery electrode materials. Furthermore, bismuth is non-toxic to the natural environment surrounding the battery; it has a surprisingly high power density of 386 mAh g−1 and a volume power density of 3800 mAh L−1. Bismuth's inherent volume expansion as a negative electrode (PIBs is about 411%) and electrode pulverization are issues, although reversibility can be increased by coordinating the Bi-metal center with potassium ions.123 Based on this idea, Sun et al.124 used a solvothermal method to synthesize a new flower-like Bi-MOF assembled from two-dimensional porous nanosheets, and further calcined it with melamine as a nitrogen source in an Ar atmosphere to obtain Bi@N-CNCs. The 850Bi@N-CNCs were then improved for further use as anode materials in PIBs. The reversible capacities of the electrodes were measured to be 334.3 mAh g−1 and 221.3 mAh g−1 at current densities of 0.5 and 10.0 A g−1, respectively. The loss of capacity per cycle over 1200 cycles at 5.0 A g−1 was 0.004%.
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Fig. 6 (a) Co-MOF-rGO hybrid material preparation schematic; (b) hybrid anode's charge and discharge curves; (c) hybrid anode cycling performance; (d) hybrid and standard PIB anode comparison; (e) cycling performance of the hybrid anode at the rate of 2 A g−1 for 2000 cycles; (f) CV graphs showing increasing scan speeds for the hybrid material between 0.05 and 1 mV s−1. Reproduced with permission from ref. 122, Copyright 2020 American Chemical Society. |
Recently, Li et al.121 used terephthalic acid and bismuth as anode materials for potassium ions to create a 3D structured Bi-MOF. The three-dimensional porosity effectively avoided the volume expansion problem and enhanced the ion transport capacity by distributing the stress during the alloy reaction. When Bi-MOF was employed as the negative electrode material of PIB, the reversal ability was 415 mAh g−1 and cycle stability was 315 mAh g−1 at a current density of 0.5 A g−1. For potassium storage purposes, several researchers have also mixed selenides with porous carbon composites. The Bi/Bi3Se4@CNR composite material, which is made up of internal Bi/Bi3Se4 nanoparticles and an exterior rod-like porous carbon skeleton, was created by Chen et al.125 by hydrothermally synthesizing Bi-MOF and then pyrolyzing and seleniuming it in an Ar environment. Bi/Bi3Se4 nanoparticles are uniformly dispersed and protected by the sturdy outer carbon rod structure. The carbon rod's ample buffer area also prevents the nanoparticles from expanding, significantly increasing the rate capacity and cycling stability. With its excellent reactivity and endurance, the synthesized material was selected as the anode material. In situ characterization demonstrated that the dual mechanisms of conversion and alloying/de-alloying governed the potassiumation/depotassiumation process. The reason potassium can be stored in the Bi/Bi3Se4@CNR composite is because of a series of steps. At the start, a reversible formation of a solid electrolyte interphase (SEI) layer occurs and then Bi3Se4 is irreversibly converted to Bi and K2Se at around 1.04 V. From there, Bi forms K3Bi with K+ in an alloying reaction, which is caused by low voltages (0.46 and 0.36 V). In the anodic process, K3Bi allows Bi to be freed and de-alloyed, as shown by the peaks at 0.46, 0.54 and 0.64 V. Meanwhile, the peak at 1.14 V verifies that the material can store potassium. The battery had a reversible capacity of 307.5 mA g−1 for lithium, and the capacity preserved after 2000 cycles at a current density of 5 mA g−1 was 254.8 mA g−1.
Li et al. established a straightforward approach for encapsulating Sn sub-nanoclusters in a nitrogen-doped multichannel carbon matrix for use as a flexible anode material for high-performance PIBs (Fig. 7a).126 The Sn-SCs@MCNF electrode's galvanostatic charge–discharge (GCD) patterns are shown in Fig. 7b. The clear voltage plateaus observed throughout the charge/discharge processes and the CV analysis match up nicely. The electrode initially had a coulombic efficiency of 40.2% because of its discharge/charge capacity of 1289 and 519 mAh g−1, respectively. Fig. 7c–e illustrates the related charge/discharge patterns, rate capabilities, and cycle performance at varied current densities. The cell exhibits an unrivaled reversible capacity of around 167 mAh g−1 even after 200 cycles and a current density of 0.4 A g−1. Even after 5000 cycles, the electrode maintained a continuous discharge capacity and an average CE of ∼99%, outperforming most Sn-based anodes and other PIBs. The Sn-SCs@MCNF electrode's remarkable potassium storage performance is primarily due to its ultra-small Sn sub-nano clusters and unique multichannel nano-architecture, which not only guarantees electrodes with enough active sites and pathways for electron and ion quick transportation but also offers a very stable framework that is advantageous for superior cycling stability. Nyquist plots and the long-term cyclic stability of the synthesis scheme are shown in Fig. 7f–h. Table 3 presents the performance of MOFs as advanced materials for potassium-ion battery applications.
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Fig. 7 The electrochemical performance of the as-prepared PIB anodes: (a) CV curves intersect at different voltage ranges; (b) current profiles of Sn-SCs@MCNF at a rate of 100 mA g−1; (c) performance over repeated cycles; (d) rate capability; (e) charge/discharge patterns of Sn-SCs@MCNF at varying current densities; (f) Nyquist graphs (the corresponding equivalent circuit is inset) produced after 100 cycles; (g) stability of long-term cycles at a high rate of 2.0 A g−1; (h) diagrammatic representation of the synthesis pathway leading to Sn-SCs@MCNF. Reproduced with permission from ref. 126, Copyright 2024 Wiley. |
Pristine MOFs | Application | Cycle number | Retention capacity (mAh g−1) | Current density (mA g−1) | Ref. |
---|---|---|---|---|---|
MIL-125 | PIBs | 200 | 157 | 50 | 127 |
ZIF-67 | PIBs | 1000 | 320 | 1000 | 128 |
MIL-125(Ti) | PIBs | 200 | 157 | 0.05 A g−1 | 129 |
ZIF-67 | PIBs | 2000 | 143 | 1000 | 130 |
L-Co2(OH)2BDC | PIBs | 600 | 188 | 1 A g−1 | 131 |
ZIF-67 | PIBs | 2000 | 231.6 | 500 | 132 |
Cu-BTC | PIBs | 50 | 364 | 50 | 133 |
K-PDA | PIBs | 300 | 115 | 0.1 A g−1 | 134 |
Bi-BTC | PIBs | 600 | 225 | 100 | 135 |
MOF-235/G | PIBs | 200 | 160 | 0.2 A g−1 | 136 |
Bi-BTC | PIBs | 400 | 305 | — | 137 |
Fe-BTC | PIBs | 300 | 161 | 1000 | 138 |
MOF-235/MCNTs | PIBs | 200 | 132 | 0.2 A g−1 | 139 |
UiO-66(Zr) | PIBs | 2000 | 218 | 1000 | 140 |
Sb-BDC | PIBs | 100 | 497 | 100 | 141 |
Co-MOF-rGO | PIBs | 2000 | 207 | 2 A g−1 | 122 |
Fe/Zn-MOF-5 | PIBs | 100 | 439 | 100 | 142 |
UIO-66-NH2 | PIBs | 800 | 187 | 100 | 143 |
NH2-MIL-101(Al) | PIBs | — | 365 | 25 | 144 |
MOF-74 | PIBs | 1900 | 495 | 200 | 145 |
Co3[Co(CN)6]2 | PIBs | 200 | 297.5 | 0.1 A g−1 | 146 |
Fe-ZIF-8 | PIBs | 200 | 268 | 100 | 147 |
ZIF-8/Cu | PIBs | 500 | 315 | 50 | 148 |
The electrochemical performance of negative electrode materials in potassium-ion batteries has been successfully enhanced by MOF composite materials that include external carbon-based components such as graphene and graphene oxide. Two-dimensional, three-dimensional structures and metal selenides have also shown great potential in potassium-ion battery negative electrode materials in recent years.
To effectively minimize the shuttling effect of polysulfides, long-chain polysulfides generated at the positive electrode of alkali metal–sulfur batteries can dissolve in conventional electrolytes. This dissolution allows them to migrate to the negative electrode, causing irreversible losses and negatively impacting battery performance.149 Zheng et al.150 designed a Ni-MOF and discovered that the Lewis acidic Ni(II) center interaction and the Lewis alkalinity of polysulfides capture polysulfides in the MOF skeleton, enhancing its cycle stability. This confirmation of polysulfide absorption based on Lewis acid–base theory has helped improve the design ideas of such battery materials. Bai et al.151 created and constructed a lithium–sulfur battery microporous MOF@GO separator with regular pores with a pore size of about 9 Å, effectively blocking the passage of polysulfide ions. In lithium–sulfur batteries, the MOF-based separator functions as an ionic sieve, effectively inhibiting undesirable polysulfides that migrate to the anode side while selectively sieving Li+ ions. In a lithium–sulfur battery with an MOF-based separator, a sulfur-containing mesoporous carbon material (around 70 weight percent sulfur content) employed as a cathode composite without complex synthesis or surface modification showed a low capacity decay rate (0.019% per cycle over 1500 cycles). Based on previous ideas for preparing MOF membranes, Li et al.152 recently developed a functional membrane for lithium–sulfur batteries by in situ growth of sodium alginate fiber membranes with ZIF-67 by electrospinning (Fig. 8a). ZIF-67 was loaded in situ onto a polyacrylonitrile (PAN) matrix to generate this SA fiber membrane, a unique type of multifunctional lithium–sulfur battery membrane (ZIF-67/SA-PAN). It can effectively isolate polysulfides. Li–S batteries with the ZIF-67/SA-PAN separator have significant reversible potential and long cycle life of 500 cycles at 1C. They discovered that the cell had a greater oxidation current density of 0.428 V and a narrower voltage gap of redox peaks of 384 V, as evidenced by the CV curves in Fig. 8b. The redox kinetics of LiPs may be considerably enhanced by ZIF-67/SA-PAN, which is further supported by electrochemical impedance spectroscopy studies. The cell works better than the Celgard 2325 cell in terms of rate, as expected (Fig. 8c). Fig. 8d shows the cell's charge–discharge characteristics at 0.2C. Its cycle performance is superior to that of the Celgard 2325 cell (Fig. 8e), which has a longer gap between charges and discharges. The battery's activation phase is the reduction in the capacity during the initial cycles. The cycle performance with sulfur loading is shown in Fig. 8f. After 500 cycles, with an average decay rate of 0.089% for each cycle, it gives a significant capacity of 445 mAh g−1 (Fig. 8g). The pouch cell for illuminating an LED design is shown in Fig. 8h.
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Fig. 8 (a) ZIF-67/SA-PAN synthesis and a Celgard 2325 lithium–sulfur battery separator; (b) CV curves at a rate of 0.1 mV s−1; (c) performance rating; (d) charging and discharging properties of the synthesized cell; (e) charge and discharge properties of the synthesized cell; (f) cell capacity to cycle at 0.1C while having a 5.45 mg cm−2 sulfur loading; (g) cycling capability of the cells; (h) illustration of pouch cell-illuminated LED design. Reproduced with permission from ref. 152, Copyright 2022 American Chemical Society. |
Geng et al.153 prepared MIL-96-Al of different shapes and sizes, analyzed the effects of shape and size on its electrochemical performance, and provided improved ideas for the size design of MOF materials. Sulfur usage declines with decreasing crystal size, as demonstrated by the cyclic performance, which showed that the cyclic stability decreased monotonically with increasing particle size. The different HBCs have initial specific capacities of 940.9, 883.7, 847.8, 1235.4, and 1083.4 mAh g−1, in that order. The specific capacities after 200 cycles were 217.5, 279.4, 389, 367.8, and 448 mAh g−1. This suggests that cyclic performance improves as the particle size decreases because the pore volume progressively improves with decreasing host particle size.154 Therefore, more sulfur can permeate the host's free space and lessen the loss of active molecules. Using a MIL-96-based cathode in Li–S batteries, sulfur stays confined in the MOF porous material and participates in redox reactions during each charge and discharge. After discharging, S8 changes into soluble lithium polysulfides (Li2Sx) and these eventually turn into solid Li2S2/Li2S. The MIL-96 system, due to its HBC structure with many (101) planes, helps bind polysulfides and blunts the shuttle effect. A reduction in crystal size helps more sulfur be utilized by making the electrolyte, electrons and Li+ move more easily. Li2S2/Li2S is oxidized to pure S8 during the process of charging, which marks the end of the cycle. In this structure, there is enough space for ions, less polarization and the electrodes maintain their electrochemical properties for long periods.
To prevent dendritic development on the alkali metal negative electrode of lithium–sulfur batteries, Song et al. synthesized Bio-MOF-100 and carbonized it for 8 hours at 800 °C in an Ar environment to produce ZnENC, an amorphous carbon material. ZnENC and Bio-MOF 100 were applied to both sides of the Celgard separator to create a novel SAZ AF Janus separator.155 Even at high current densities, dendrite development must be prevented by the uniform and quick transit of lithium ions, which is easily provided by the double layer of Bio-MOF-100 placed on the separator side in contact with the lithium negative electrode. Increasing the number of metal nodes in MOF materials might effectively maximize their application in lithium–sulfur batteries. This is because MOF materials can enhance polysulfide absorption in lithium–sulfur batteries by including bimetallic and multimetallic nodes. In their recent work, Zhu et al. proposed that the precursor Ni-ZIF-67 can be annealed and phosphating at high temperature to encapsulate Ni–Co bimetallic phosphide in a nitrogen-doped dual-carbon conductive network (Fig. 9a).156 The catalytic conversion of lithium polysulfide may be considerably improved by the encapsulated Ni/Co phosphide particles. With a redesigned separator, lithium–sulfur batteries exhibit exceptional cycle stability and a high specific capacity of 1083.4 mAh g−1 at 0.5C (Fig. 9b–f). The synthesis of multi-metal doping can also be carried out by either a one-pot synthesis or an ion-exchange technique where single metal MOFs are subjected to metal-ion solutions at varying concentrations.157 Li et al. created many Mn-based multimetallic MOFs using a one-pot synthesis technique, including trimetallic and bimetallic MIL-100 nano-octahedral. To prepare cathodes for Li–S batteries, multimetallic Mn-based MIL-100 nano-octahedra are used as sulfur hosts.158 These nano-octahedra's symmetrical structure, modifiable composition, coordinatively unsaturated metal sites, and regular porosity appear to be beneficial advantages for improving Li–S battery performance. The testing of MnNiMIL-100@S positive electrode showed the best lithium–sulfur battery performance followed by the 708.8 mAh g−1 after 200 cycle attainment. Table 4 presents the performance of MOFs as advanced materials for lithium–sulfur battery applications.
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Fig. 9 (a) Fabrication of the NiCoP@NC-modified separator; (b) CV conducted at a scan rate of 0.1 mV s−1; (c) discharge–charge profiles; (d) rate performance at various rates; (e) cycle performance at 0.5C for an extended duration; (f) cell profiles at 1C utilizing a NiCoP@NC//PP separator. Reproduced with permission from ref. 156, Copyright 2023 Elsevier. |
Pristine MOFs | Application | Cycle number | Specific capacity (mAh g−1) | Current density | Ref. |
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ZIF-8 | LSBs | 300 | 553 | 0.5C | 159 |
MIL-88A | LSBs | 1000 | 300 | 0.5C | 160 |
Mn-CCs | LSBs | 200 | 990 | 0.2C | 161 |
Zn-MOF | LSBs | 200 | 609 | 0.2C | 162 |
MIL-100(Cr) | LSBs | 60 | ∼450 | 0.1C | 163 |
MIL-100(V) | LSBs | 200 | 292 | 0.1C | 164 |
HKUST-1(Cu) | LSBs | 170 | 240 | 0.1C | 165 |
MOF-525(2H) | LSBs | 200 | 402 | 0.5C | 166 |
Ni6(BTB)4(BP)3 | LSBs | 100 | 611 | 0.1C | 150 |
MIL-101(Cr) | LSBs | 50 | 650 | 0.2C | 167 |
MIL-101(Cr) | LSBs | 134 | 847 | 0.8C | 168 |
MIL-101(Cr) | LSBs | 192 | 607 | 0.1C | 169 |
MIL-101(Cr) | LSBs | 400 | 320 | 5C | 170 |
MIL-53(Al) | LSBs | 100 | 900 | 0.5C | 170 |
NH2-MIL-53(Al) | LSBs | 300 | 332 | 0.5C | 159 |
HKUST-1(CuBTC) | LSBs | 1000 | 250 | 0.2C | 171 |
Tannic acid tuned ZIF-67 | LSBs | 100 | 757 | 0.1 A g−1 | 172 |
Co6 (BTB)4(BP)3 | LSBs | 200 | 400 | 0.2C | 150 |
MOF-525(FeCl) | LSBs | 200 | 616 | 0.5C | 166 |
MOF-525(Cu) | LSBs | 200 | 704 | 0.5C | 166 |
nMOF-867 | LSBs | 500 | 700 | 0.5C | 173 |
nUiO-67 | LSBs | 500 | 450 | 0.5C | 173 |
Mn-BTC | LSBs | 80 | 1100 | 0.1C | 174 |
Ni3(HITP)2 | LSBs | 500 | 716 | 1C | 175 |
Ni3(HITP)2 | LSBs | 300 | 585.4 | 0.5C | 176 |
Modified diaphragms based on MOF materials and their derivatives can effectively adsorb polysulfides when used in metal–sulfur batteries. When used as a coating layer to prepare a separation membrane with an asymmetric structure, it can induce uniform deposition of lithium-negative electrodes to a certain extent. Additionally, multi-metal MOFs exhibit superior electrochemical performance when used to fabricate positive-electrode sulfur carrier materials.
Due to their structural characteristics, MOF materials are often used to prepare ion sieves to reduce the generation of zinc anode dendrites. However, these prepared ion sieves are still vulnerable to serious polarization and dendrite formation after many cycles on the ZMB.180 Lei et al.181 experimentally demonstrated that two-dimensional MOF nanosheets can be used as a protective coating to inhibit dendrite formation. The two-dimensional structure has a higher concentration of Zr–OH/H2O zinc-philic sites, which can induce uniform Zn deposition and better inhibit zinc dendritic growth, the researchers confirmed when comparing the differences between UiO-67-3D and UiO-67-2D materials as zinc anode coatings. Additionally, the UiO-67-2D@Zn‖Mn2O3/C battery with this coating demonstrated outstanding cycle stability, rate performance, and reversible capacity. A MOF coating on the Zn surface was proposed by Yang et al. for MnO2–Zn high-performance batteries. The MOF coating layer was constructed to achieve homogeneous Zn deposition and thus prevent the dendritic growth of the Zn-negative electrode (Fig. 10a and b).182 Fig. 10c shows a schematic representation of highly coordinated H2O–Zn2+·OSO32− migration of ion complexes via MOF channels. It is evident from cycles 20 to 150 in the selected curves that the discharge/charge profiles of the MOF-coated Zn anodes were nearly identical to the declining patterns of the naked Zn anodes. With a capacity of 67.3% and a current density of 500 mA g−1, the control group exhibited a comparable activation process over the first 20 cycles. However, the particular capacity decreased with time from 188.4 mAh g−1 to 129.1 mAh g−1. At a current density of 0.5 mA cm−2, the symmetric Zn half-cell remained stable for up to 3000 h. Fig. 10d and e show the initial charge/discharge and voltage curves for the MOF-coated (bottom) and bare (top) zinc anodes. When the quantity of MnO2 loading was 4.2 mg cm−2, a high practical capacity of 180.3 mAh g−1 was obtained using a MnO2 positive electrode. After 600 cycles, the capacity retention rate was 88.9% (Fig. 10f). Likewise, UIO series MOFs were employed to address the design and issue of dendrite formation of the Zn-negative electrodes. Xu et al.183 prepared a UiO-66 defect layer and further prepared a defective MOF (D-UiO-66) on the zinc surface, and then used it and two zinc salt electrolytes to form a quasi-solid interface phase as a zinc ion reservoir (Fig. 10g). By understanding the anion adsorption and the transfer effectiveness of zinc ions on the Lewis acid sites in the defective layer of MOFs, the near-anode zinc concentration can be enriched, which can support the discouraged growth of zinc dendrites. The suggested quasi-solid interphase in the Zn‖Cu cell achieved an average coulombic efficiency of 0.998. The viability of the quasi-solid interphase is supported by the cycling performance of D-UiO-66@Zn‖MnO2 (about 92.9% of its initial capacity after 2000 cycles) and D-UiO-66@Zn‖NH4V4O10 (approximately 84.0% of its initial capacity after 800 cycles) (Fig. 10h–k).
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Fig. 10 Diagrammatic representation of Zn's surface development: (a) on bare Zn foil, assault from the desolvation process results in significant water passivation and dendritic development; (b) method by which the MOF coating layer creates a super-saturated front surface and rejects H2O; (c) diagrammatic representation of H2O–Zn2+·OSO32− highly coordinated ion complexes moving through MOF channels; (d) MnO2–Zn cells' initial discharge/charge curve with MOF-coated Zn and a blank Zn anode; (e) MOF-coated Zn anode (bottom) and bare Zn anode (top) voltage profiles; and (f) MnO2–Zn cells' cyclic stability at a 500 mA g−1 current density. Reproduced with permission from ref. 182, Copyright 2020 Wiley. (g) Diagram showing the D-UiO-66 layer's synthesis pathway Zn‖NH4V4O10 whole cells' performance; (h) Zn‖NH4V4O10 whole cells' long-cycling performance and associated discharge patterns; (i) with and (j) without a quasi-solid interphase based on D-UiO-66; (k) rate performance of Zn‖NH4V4O10 complete cells with and without quasi-solid interphase based on D-UiO-66. Reproduced with permission from ref. 183, Copyright 2023, Springer. |
Zhang et al. employed a one-pot in situ solvothermal strategy to investigate the Mn-MOF/CNT composite as a ZIB cathode.184 Following the addition of CNTs, the highly interpenetrated Mn-MOF framework created a conductive network, which improved the surface area, conductivity, and chemical stability. The ZIBs' high capacity of 260 mAh g−1 at 50 mA g−1 allows them to cycle effectively, and even after 900 cycles at 1000 mA g−1, they could still hold nearly 100% of their capacity. An aqueous zinc ion battery's new quinone-containing copper-catecholate MOF cathode was created by Liu et al. in a different study.185 The Cu-TBPQ MOF has several redox-active sites, high conductivity, and significant porosity, making it an ideal cathode material for zinc-ion batteries. The Cu-TBPQ MOF shows a capacity of 120.3 mAh g−1 and a current density of 2.0 A g−1 after 500 charge–discharge cycles, demonstrating high rate capability and cycle longevity. The MOF uses a redox process in which the reactions at copper centers and organic ligands operate simultaneously to store zinc ions [Zn2+]. While being discharged, Cu2+ in the [CuO4] groups becomes partially Cu1+ and the quinone groups can exchange their CO bonds with C–O bonds. Because Zn2+ ions fit into the pores of the MOF, the framework slightly shrinks without damaging its structure. Charging the battery makes Cu+ change to Cu2+, transforms quinone groups and removes the Zn2+ ions that were previously present. The presence of two redox processes and a strongly connected π-conjugated structure supports the anode's high capacity, strong stability and good Zn2+ retention. The work's successful redox-active site enrichment results in new opportunities for the logical design of electrochemically active 2D c-MOFs, increasing their potential for cutting-edge energy storage applications.
Since altering the intrinsic structure is a useful modification method to enhance electrochemical performance, researchers have shown that steric hindrance in the lattice region decreases the efficiency of zinc ion transmission. To achieve this, Ren et al.186 developed artificial SEI membranes using amorphous metal–organic framework materials (aMOFs) created by a one-step solvothermal process with Zr4+ and ATMP. The use of aMOFs in aqueous zinc-ion batteries was made possible by their improved zinc-ion transmission and uniform deposition, which are based on flaws, dangling bonds, and microporous architectures that differ from crystalline MOFs. An artificial SEI made from amorphous MOF (AZ) protects Zn anodes in AZIBs with help from defects, open porosity and a strong negative charge for efficient Zn2+ migration, ion adsorption and drying of [Zn(H2O)6]2+ ions. Because the surface of a zinc-ion battery has many hydrogen bonds, it helps Zn2+ move and discourages corrosion and dendrite growth. With AZ-coated Zn (AZ-Zn), the symmetric cells can work for 1800 h at 1 mA cm−2 with 31 mV extra potential; and at 10 mA cm−2, they can cycle for 953 h with the same over potential. Furthermore, using the concept of unsaturated coordination, Yin et al. created positive electrode materials.187 By altering the molar ratio of Mn and H3BTC throughout the synthesis, three Mn-based MOFs with varying degrees of coordination in their structures were created (Fig. 11a). The Prussian blue analogue with a COOH/Zn2+ molar ratio of 1:
4 exhibited the highest Zn2+ storage capacity compared to the other observed ratios. Another set of experiments has also shown that at 100 mA g−1 it has a wonderful capacity of 138 mAh g−1 further endorsing this finding. The charge/discharge poles and aqueous electrolyte of MOF cathode-Zn anode ZIBs are shown in Fig. 11b–d. The observed electrochemical performance difference between Mn-H3BTC-MOF-4 after 1500 cycles and a 93.5% capacity retention rate might result from two aspects. (i) The ideal degree of unsaturated coordination maximizes the ionic and electronic conductivity of MOFs, and (ii) Zn2+ ions can reversibly intercalate into the MnO2 channel to boost the capacity of the aqueous Zn(CF3SO3)2 electrolyte. Fig. 11e–g show the rate capabilities of the CV curves (between 100 and 3000 mA g−1).
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Fig. 11 (a) Diagrammatic depiction of the Mn(II) production and coordination environment in Mn-H3BTC-MOF-4; (b) diagram of ZIBs using an aqueous electrolyte and MOF cathode-Zn anode; (c and d) charge and discharge curves at various current densities; (e) charge and discharge curves for three samples at 100 mA g−1 and 0.1 mV s−1; (f) rate capacities between 100 and 3000 mA g−1; (g) performance of composite cycling. Reproduced with permission from ref. 187, Copyright 2021 American Chemical Society. |
To create an alternatingly stacked Cu-HHTP/MX heterostructure that can be utilized in aqueous zinc-ion batteries, Wang et al. recently proposed employing 2D-MOF materials created via a solution phase-direct assembly process. MOF cathode-Zn anode ZIBs were designed with an aqueous electrolyte and charge/discharge poles. Two factors may be responsible for the reported electrochemical performance differential of Mn-H3BTC-MOF-4 after 1500 cycles and a 93.5% capacity retention rate.188 Liu et al. successfully used a precise surface grafting process to develop a range of MOF-functionalized electrospun polyacrylonitrile nanofiber separators. These separators were used to separate aqueous zinc (Zn)-ion batteries and were incredibly effective.189 MOF-NS exhibits significant ionic conductivity (22.81 mS cm−1), cyclic durability, and a good Zn2+ transference number (0.78). The theoretical simulations demonstrated that the desolvation processes of hydrated Zn ions and the successfully accelerated dissociation of zinc salts through strong ion–dipole interactions can contribute to these enhanced capabilities. Using an MOF-assisted method, Zhang and associates produced newly carved Ce ions that intercalated porous V2O5 nano-belts and functioned as a stable ZIB cathode.190 After 100 cycles, the Ce–V2O5 nano-belts maintained 99.2% of their capacity and could discharge 395 mAh g−1 at 0.1 A g−1. During the charge/discharge process, pre-intercalated Ce ions can reduce the electrostatic connection between Zn2+ and the host structure in addition to effectively increasing the conductivity of the whole material and acting as stable pillars to increase the interlayer spacing of V2O5. The excellent electrochemical performance was made possible by MOF derivative-based electrode materials with adjustable porosity characteristics that inhibited self-aggregation and maintained their original morphologies. To create hierarchically ordered V2O3/V3O5/Zn2VO4@NC (ZnVO-800) submicron particles, Wu et al.191 presented a novel self-sacrificing technique (Fig. 12a). By expanding the contact interface between the cathode material and electrolyte and decreasing the ion diffusion channels, hierarchical heterojunctions produced quick kinetics and long-term cycling. ZnVO-800's long-term cycling performance was assessed at various current densities (Fig. 12b). The corresponding capacity retention rates were 92.5%, 56.9%, and 95.1%, respectively. At 0.5 A g−1, the ZnVO-800 electrode exhibited a high initial discharge capacity of 314.0 mAh g−1. Compared with the ZnVO-700/ZnVO-900 electrode, the ZnVO-800 electrode demonstrated a greater discharge capacity under the same conditions (Fig. 12c–f). According to the electrochemical mechanism, an in situ electrochemical activation process converts the ZnVO-800, which has low electrochemical properties, into ZnxV2O5·nH2O, which has high electrochemical activity. Zn2+/H+ is then reversibly added to or removed from the cathode material. In addition to improving the contact interface between the electrolyte and cathode materials, the hierarchical heterojunction can shorten the ion diffusion path, promoting quick dynamics and long-term cyclability.
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Fig. 12 (a) Diagrammatic representation of ZnVO-800 synthesis; (b) CV curve; (c) profiles of galvanostatic charge–discharge in ZnVO-800; (d) cycling performance of ZnVO-800; (e) comparison of ZnVO-800's cycling performance after activation at 0.5 A g−1 current density; (f) cycling performance of ZnVO-before activation. Reproduced with permission from ref. 191, Copyright 2023, Elsevier. |
The V2O3/V3O5/Zn2VO4@NC (ZnVO-800) composite stands out for its exceptional cycle ability, which even after 3000 cycles retains 90.8% of its capacity and its high reversible capacity of 100.1 mAh g−1. The electrochemical mechanism shows that an in situ electrochemical activation process converts ZnVO-800, which has low electrochemical properties, into ZnxV2O5·nH2O, which has excellent electrochemical activity. Table 5 presents the performance of MOFs as advanced materials for zinc-ion battery applications.
Pristine MOFs | Application | Cycle number | Specific capacity (mAh g−1) | Current density (mA g−1) | Ref. |
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ZIF-7 | ZIBs | 20/180 | 188.4/129.1 | 500 | 182 |
ZnMOF-808 | ZIBs | 50 | 125 | 0.2 A g−1 | 192 |
ZIF-8@Zn | ZIBs | 900 | 112 | — | 193 |
Mn-H3BTC-MOF-4 | ZIBs | 1000 | 138 | 100 | 187 |
ZIF-67 | ZIBs | 1000 | 288 | 0.05 A g−1 | 194 |
Mn(BTC) | ZIBs | 900 | 92% | 1000 | 195 |
V-MOF//Zn | ZIBs | 86 | 86 | 1000 | 196 |
Cu3(HHTP)2 | ZIBs | 500 | 124.4 | — | 197 |
Ni,Cu-MOF | ZIBs | 1500 | 1837C g−1 | 500 | 198 |
Mn2O3-MOF | ZIBs | 500 | 154.8 | 1000 | 199 |
CoFe(CN)6 | ZIBs | 2200 | 93.4% | 3 A g−1 | 200 |
Mn-H3BTC-MOF-4 | ZIBs | 1000 | 93.5% | 3.0 A g−1 | 187 |
Conductive V-MOF (MIL-47) | ZIBs | 300 | 81.5% | 2 A g−1 | 201 |
UiO-66 | ZIBs | 500 | 240 | 3 mA cm−2 | 202 |
ZIF-L | ZIBs | 800 | 297.5 | 4 mA cm−2 | 203 |
ZIF-7 | ZIBs | 600 | 180.3 | 0.5 mA cm−2 | 182 |
ZIF-8 | ZIBs | 900 | 100 | 0.25 mA cm−2 | 195 |
ZIF-8 | ZIBs | 300 | 266.5 | 2 mA cm−2 | 204 |
Zn-BTC | ZIBs | 1000 | 116.6 | 1 mA cm−2 | 205 |
Zr-MOF | ZIBs | 500 | — | 10 mA cm−2 | 197 |
ZIF-8 | ZIBs | 100 | 50 | 2 mA cm−2 | 206 |
Ti-MOF | ZIBs | — | 256 | 5 mA cm−2 | 207 |
MOF-CeO2 | ZIBs | 10![]() |
163 | 3 mA cm−2 | 208 |
Cu3(BTC)2 | ZIBs | 350 | 270 | 0.5 mA cm−2 | 209 |
The use of MOF materials to produce coatings effectively reduces the problem of zinc anode dendrite development in aqueous zinc-ion batteries, and their intrinsic structural control presents a fresh idea for enhancing zinc-ion storage and transmission capabilities.
Sheberla et al. advocated using pure Ni3(HITP)2 as the active material for EDLCs. It was the first pure MOF material to be employed as an electrode for double-layer capacitors due to its excellent electrochemical characteristics. Effective ion transport is made possible by the dense microstructure of Ni(HITP)2 pellets, which are generated under 100 kg-force per cm2 pressure and have particle sizes ranging from 0.5 to 2 μm and holes of similar sizes. The electrodes had a density of about 0.6 g cm−3 and a mass loading of ≥7 mg cm−2. The large cylindrical pores contributed to the excellent capacitive performance, and the packed, porous shape was confirmed by SEM. The structure of Ni3(HITP)2 is perfect for high-performance supercapacitors because it performs better than most carbon materials, with a surface area-normalized capacitance of 18 μF cm−2.216 Liang et al.30 reviewed the applications of basic MOFs and composite MOFs and discussed their development strategies for supercapacitor electrode materials. Most basic MOFs are prone to collapse in acidic and alkaline application environments. Therefore, a series of ideas were proposed: (1) by adding multi-metals to the MOF-74 series, the redox behavior is enhanced in terms of charge–discharge curves with constant current and cyclic voltammetry; (2) in UiO-based MOFs, the ligand's sp2 hybridized nitrogen atoms can enhance the interaction with ions; (3) nMOF-867 is a sample with suitable particles and pore size for synthesizing nMOF. In addition, in the research of MOF composite materials, highly conductive materials (such as graphene, GO, rGO, CNTs and conductive polymers) are combined with original MOFs to further synthesize MOF composite materials, which can speed up research on SCs electrode materials and increase the conductivity of original MOFs.217,218 Fan et al. used 3D-functionalized graphene oxide (FGO) to attach and disseminate Co-MOF-74 nanoparticles after adding Co to MOF-74. These nanoparticles were then employed as negative electrode materials in sodium-ion hybrid capacitors (SIHC).219 At a current density of 0.1 A g−1, the produced electrode's specific capacity is 1170 mAh g−1. Approximately 416 mAh g−1 is the electrode's reversible capacity after 100 cycles at the same current intensity. The performance of the Co-MOF-74|FGO180//AC device was excellent (Fig. 13a). With an energy density of 240 Wh kg−1 and a maximum power density of 10 kW kg−1, it exhibits remarkable cycle stability. The electrode's rate performance at different current densities, cycle performance, and corresponding discharge–charge voltage profiles are shown in Fig. 13b–d. The following characteristics of the Co-MOF-74|FGO-180 electrode may be responsible for its exceptional cycle stability and maximum reversible capacity: (1) Co-MOF-74 is a honeycomb structure that has a lot of active sites for storing sodium ions and adequate one-dimensional channels for complete electrolyte penetration; (2) the development of MOFs is inhibited by the confinement effect of FGO, resulting in ultra-fine nanocrystals that may shorten the ion transport route; and (3) graphene's exceptional conductivity facilitates electron transport and quick kinetics. FGO wrapping may also minimize volume expansion caused by desodiation or sodiation, maintain enough interface contact, prevent Co-MOF-74 from clumping together, and strengthen the electrode material's structural integrity. After 200 cycles, the reversible charge capacity can maintain 303 mAh g−1 at 0.5 A g−1, with a high CE approach of nearly 100%, as shown in Fig. 13e.
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Fig. 13 (a) CV curves for Co-MOF-74|FGO-180 electrodes; (b) electrode rate performances of all three materials; (c) electrode voltage curves at various densities; (d) electrode cycling performance and coulombic efficiency at 0.1 A g−1 for 100 cycles; (e) schematic representation of the electrode is shown in the inset. Reproduced with permission from ref. 219, Copyright 2023 Elsevier. (f) Procedures for Co3S4/Ti3C2Tx and ZIF-67/Ti3C2Tx synthesis; (g) CV curves for the electrodes acquired at 5 mV s−1; (h) Co3S4/Ti3C2Tx//AC ASC CV curves at 10 mV s−1, various potential levels, and scan speeds ranging from 5 to 100 mV s−1; (i) Co3S4/Ti3C2Tx//AC ASC, cycle stability at 5 A g−1 current density. Reproduced with permission from ref. 220, Copyright 2022, Elsevier. |
The novel composite materials ZIF-67/Ti3C2Tx and Co3S4/Ti3C2Tx were described by Luo et al.220 using hydrothermal and precipitation techniques as positive electrode materials (Fig. 13f). The hybrid ZIF-67/Ti3C2Tx material produced showed outstanding cycle stability and rate performance. Ti3C2Tx incorporation into the ZIF-67 enhances the hybrid material's structural stability and electrical conductivity, enabling it to serve as a support. ZIF-67/Ti3C2Tx was sulfidated to produce Co3S4/Ti3C2Tx, which showed pseudocapacitive behavior. At 1 and 10 A g−1, the Co3S4/Ti3C2Tx-containing electrode's highest specific capacitance values were 602 and 491 F g−1, respectively. Fig. 13g and h shows the Co3S4/Ti3C2Tx//AC ASC CV curves, with scan speeds varying from 5 to 100 mV and various potential levels. With a high energy density of 44.9 Wh kg−1 and a power density of 800.3 W kg−1, the asymmetric devices can cycle more than 5000 times (Fig. 13i). This outstanding performance was comparable in certain situations, even better than that of electrodes made of other common metal complexes.
Li et al. developed composites made of Co3O4 and three-dimensional porous carbon (3DPC) (Fig. 14a).221 These materials were prepared by pyrolyzing the 3D graphene/Co-MOF precursor. The curves for samples within a voltage window of 0–0.5 V at 100 mV s−1 depart from the desired rectangular form when pseudocapacitive activity is present. Fig. 14b–d shows CV curves for various scan speeds, as well as an electrode cycling test at 3 A g−1. Fig. 14e shows that the device's working voltage can be increased to 1.7 V. The device's specific capacitance values, calculated using GCD curves, were 60.76, 59.1, 58.2, 51.4, and 37.7 F g−1 at 1, 2, 3, 5, and 10 A g−1, respectively. Co3O4 has more active sites in its oxygen-deficient state. The electrode enhanced the capacitive performance with a high rate capability of 85.7% and a high specific capacitance of 423 F g−1 at 1 A g−1. The high-potential windows of the asymmetric supercapacitor are 1.7 V, 21.1 Wh kg−1 and 790 W kg−1 (Fig. 14f and g). The abundant carbon in 3DPC/Co3O4 is responsible for its good conductivity, which allows for enhanced electron transport. Together with the benefits of a weakly crystallized or amorphous state and a hierarchical porous structure, this could speed up ion diffusion and allow for full exploitation of the available space to obtain high capacitance. Furthermore, more active sites could be provided by the oxygen-deficient Co3O4 to increase the pseudocapacitive capacity. The 3DPC/Co3O4 composite improved the electrochemical performance of supercapacitor electrodes because of these benefits.
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Fig. 14 (a) Diagram showing how the materials were synthesized; (b) CV curves at 100 mV s−1 for the 3DHG, 3DHG/Co-MOF, and 3DPC/Co3O4 electrodes; (c) 3DPC/Co3O4 electrode CV curves at various scan speeds; (d) 3DPC/Co3O4 electrode cycling test at 3 A g−1; (e) 3DPC/Co3O4/AC asymmetric supercapacitor electrochemical performance; (f) CV curves at 100 mV s−1; and (g) specific capacitance and GCD curves. Reproduced with permission from ref. 221, Copyright 2020, Elsevier. |
Dubey et al. developed a cost-effective high-surface-area Cu-metal–organic framework (Cu-MOF) using residual PET plastic such as PANI (polyaniline) and PPy (polypyrrole).222 ANI and PPy not only increase the nanocomposite's conductivity but also create more MOF–PANI–MOF transport channels, which guarantee effective electrolyte-ion transport and improve the overall electrochemical performance. At a current density of 0.5 A g−1, both nanocomposites exhibited higher specific capacitances of 160.5 and 132.5 F g−1 than virgin Cu-MOF (104.8 F g−1). Additionally, asymmetric hybrid supercapacitors have been built and have shown great promise as energy storage devices. At a power density of 474 W kg−1, the Cu-MOF//Cu-MOF/PANI hybrid device achieved a high energy density of 51.4 Wh kg−1 with just 6.6% attenuation after 10000 charge–discharge cycles, demonstrating exceptional cyclic stability. Electric double-layer charging from the Cu-MOF and quick redox reactions in the PANI combine to work in the Cu-MOF/PANI supercapacitor. The Cu-MOF offers numerous accessible sites for ions, and PANI exhibits good pseudocapacitance because it can readily convert between its charged states. A well-arranged PANI nano-network provides conductive pathways for ions and electrons, thus reducing the difficulty of charge transfer. The Cu-MOF/PANI morphology has lower resistance inside the supercapacitor, responds better and performs more stably over many charge–discharge cycles than the agglomerated Cu-MOF/PPy form. Efficient redox reactions and strong structures during cycling are enabled at the Cu-MOF–PANI interface, which results in higher capacitance retention, increased energy density and better rate performance over time. Table 6 presents the performance of MOFs as advanced materials for supercapacitor applications.
MOF electrode material | Application | Current density (A g−1) | Electrolyte | Specific capacitance (F g−1) | Ref. |
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Ni3(HITP)2 | Supercapacitor | 0.05 | 1 M NEt4BF4 | 111 | 224 |
Cu3(HHTP)2 (nanowire) | Supercapacitor | 0.25 | 1 M KCl | 240 | 225 |
Ni3(HITP)2 | Supercapacitor | 5 mV s−1 | [EMIM][BF4] ionic liquid | 84 | 224 |
Co3(HITP)2 (exfoliated) | Supercapacitor | 0.5 | 1 M LiTFSI | 103 | 226 |
Mn3(HITP)2 (exfoliated) | Supercapacitor | 0.5 | 1 M LiTFSI | 89 | 226 |
Ni3(HITP)2 | Supercapacitor | 0.1 mA cm−2 | 0.5 M Na2SO4 | 170 | 227 |
Ni3(HAB)2 | Supercapacitor | 0.2 mV s−1 | 1 M KOH | 427 | 228 |
Ni3(HITP)2 | Supercapacitor | 1 mV s−1 | 1 M KOH | 100.8 | 229 |
Cu3(HHTP)2 | Supercapacitor | 0.05 | 1 M NEt4BF4 | 129 | 230 |
Cu3(HHTP)2 | Supercapacitor | 0.05 | [EMIM][BF4] ionic liquid | 57 | 230 |
Cu3(THQ)2 | Supercapacitor | 10 mV s−1 | 1 M KOH | 32 | 231 |
Cu3(THQ)2-BPY (pillared) | Supercapacitor | 10 mV s−1 | 1 M KOH | 66.1 | 231 |
Ni3(BHT)2 | Supercapacitor | 3 mV s−1 | 1 M LiPF6 | 245 | 232 |
Ni3(BHT)2 | Supercapacitor | 5 mV s−1 | 1 M NEt4PF6 | 36 | 232 |
Ni3(BHT)2 | Supercapacitor | 5 mV s−1 | 1 M NBu4BF4 | 31 | 232 |
Ni3(BHT)2 | Supercapacitor | 5 mV s−1 | 1 M NEt4BF4 | 29 | 232 |
Ni-MOF | Supercapacitor | 1 | 2 M KHO | 804 | 233 |
Ni-MOF | Supercapacitor | 10 | 2 M KHO | 534 | 233 |
Zn-MOF | Supercapacitor | — | 1 M H2SO4 | 251 | 234 |
Ni-MOF | Supercapacitor | 1.0 mA cm−2 | — | 988 | 235 |
Ni-MOF | Supercapacitor | 1.0 mA cm−2 | — | 823 | 235 |
MOF/PANI | Supercapacitor | 0.4 | KOH | 162.5 C g−1 | 236 |
Indumathi et al.223 created ZnCo2S4 and ZnCo2S4 on the metal–organic framework composite materials using a sonicated enhanced hydrothermal process. The synthetic composite electrode demonstrated exceptional cyclic retention for enhanced electrochemical characteristics with a specific capacitance of 550 F g−1 at 1 A g−1. The corresponding increased cyclability is directly linked to enhanced routes for electrolyte ion adsorption–desorption and higher surface adsorption sites in sheet-like nanostructures. Consequently, the material would possess more than 89.2 percent cyclic retention and efficient electrochemical characteristics.
Heteroatom doping, composite graphene oxide, multi-metal synergistic effects, and other tactics can effectively improve the electrochemical performance of MOF materials used as electrode materials for alkali-metal-ion batteries, according to the above description. To regulate the shuttle effect of polysulfides and handle challenges such as anode dendritic formation in aqueous zinc-ion batteries and supercapacitors, MOF materials can be used to construct bespoke diaphragms for lithium–sulfur batteries. High electrochemical performance electrode materials can be obtained using MOFs or their composites. The electrochemical performance of energy storage devices can be effectively improved by post-treating and combining various materials with MOFs. Amorphous MOFs and certain unsaturated coordination state management methods are also being increasingly introduced in the energy storage industry.
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Fig. 15 (a and b) Coordination geometry of Pb2+ ions, 3D framework of polyhedrons of [PbO2]∞ chains and one-dimensional channels along the c-axis; (c) Pb-MOF values for cycle life and coulombic efficiency;63 (d) Ti-MOF electrode structure; (e) Ti-MOF electrode charge and discharge graphs from a few chosen initial discharge cycles as well as the second, tenth, and fiftieth cycles at 100 mA g−1; (f) cycling efficiency at a current density of 400 mA g−1. Reproduced with permission from ref. 65, Copyright 2019 Elsevier. (g) Illustration of how Si@MOF-74-C carbonized composite matrix “encapsulation” configurations are made; (h) schematic depiction of Si@MOF-74-C; (i) ability of sandwich design electrodes with a thick Si loading to discharge active material. MOF-74 is utilized for every electrode; (j) SP-Si-MOF sandwich's potential profile. Reproduced with permission from ref. 238, Copyright 2024 American Chemical Society. |
For negative lithium-ion battery electrodes, Xia et al. described Ti-MOFs, which have a hexagonal nut shape and a stable structure (Fig. 15d–f).65 At a maximum initial discharge of 100 mA g−1, its specific capacity is 1590.24 mAh g−1, and even after 8000 cycles, it maintains its structural reversibility. The dobdc ligand's carboxyl groups function as electrochemical active sites with high specific capacity, interacting reversibly with Li+. MOF-74 (Co-based) and MOF-199 (Cu-based) were used in several high-Si loading electrode design combinations, according to Sturman et al. (Fig. 15g).238 A little increase in the capacity retention was observed for the sandwich structure with many layers (Fig. 15h). The most effective high-loading 0.5Si@MOF-c sample outperformed a standard silicon–graphite composite, maintaining 60% capacity after 100 cycles and offering a high capacity of 1000 mAh g−1 (Fig. 15i). The SP-Si-MOF sandwich's potential profile is shown in Fig. 15j.
Extensive research has also been conducted on the performance of the MIL series in the original MOF. Millange et al.239 proposed the first MIL series framework: MIL-53 as early as 2002. When the MIL series was later used in energy storage devices, the management of its pore size and structure required the selection of appropriate metal salts and organic ligands to offer a range of MIL forms, such as rod-shaped and spindle-shaped. These structures serve to maintain the original structure when the MIL series is employed as a precursor for calcination and carbonization, or as a basic template for modified materials to increase conductivity and charge storage capacity. Zhu et al. developed a disc-shaped Li4−xKx Ti5O12 derivative of MIL-125(Ti) to serve as the anode in lithium-ion batteries,240 Zhao et al. synthesized a micron-sized material for the lithium-ion battery anode by altering MIL-88A with polyoxometalate,241 and Ma et al.242 first proposed creating TB-FeOSC-NS by calcining MIL-88b(Fe) under certain conditions and utilizing it as a self-sacrificing template. The modified sheet-like heterostructure increased its performance as a lithium-ion anode material, achieving a high rate performance of 400 mAh g−1 at a high current density of 20 A g−1. The uses of the initial MOF materials are listed in Table 1. Moreover, carbon composite MOF materials can be prepared from carbon nanotubes, composite graphene oxide (GO), and other external carbon sources. For instance, to improve electrochemical performance, MOFs can be cultivated on carbon materials such as GO and CNTs.243 Using a solvothermal technique, Sung et al. created Co-MOF-74@MWCNT, an enhanced lithium–sulfur battery-positive electrode material, by combining Co-MOF-74 as an intermediate layer with multi-walled carbon nanotubes (MWCNTs).244 Moreover, graphene, a honeycomb carbon lattice sheet that is just one atom thick, can create active sites by enhancing interaction with MOFs because of its exceptional electrical conductivity and massive specific surface area.
Improving the capacity of LIBs mainly involves designing and creating MOF electrodes with a stable structure and superior electrochemical performance. The most promising of these materials are two-dimensional (2D) materials with greater aspect ratios, richer active sites, and larger specific surface areas. Liu et al. used a simple method to create distinctive Co-MOF nanosheets with a mesoporous structure and 2D flaky appearance (Fig. 16a). To achieve mass transfer, low-temperature calcination enhances the porosity and raises the specific surface area. The SEM images of the as-synthesized material are shown in Fig. 16b–e. When the calcination temperature was 200 °C, sample M2 exhibited long lifetimes and high specific capacities (1402.0 mAh g−1 after 100 cycles at 500 mA g−1 and 462.4 mAh g−1 after 300 cycles at 1.0 A g−1). The 2D flaky structure of the M2 sample and the available low-temperature calcination activation are responsible for the notable gains in cycle life and stability. These factors offer a straightforward method for creating high-quality LIB anodes at a reasonable cost.245 Because of their short ion transport pathways and customizable chemistry, two-dimensional (2D) MOFs show tremendous potential as high-energy anode materials for next-generation lithium-ion capacitors (LICs). A bottom-up approach was used to create ultrathin 2D Co/Fe-BDC nanosheets, which can be produced at high throughput (Fig. 16f). For Co/Fe-BDC anodes, in/ex situ findings also show highly reversible insertion/extraction processes along with crystalline-to-amorphous transitions. The high energy density (199.7 Wh kg−1) and power density (10000 W kg−1), along with exceptional cycle longevity, are provided by LICs with an ideal Co4Fe-BDC anode (Fig. 16g–i).246
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Fig. 16 (a) Diagrammatic representation of the calcined 2D Co-MOF production process; (b–e) SEM images of the as-synthesized 2D Co-MOF. Reproduced with permission from ref. 245, Copyright 2023 American Chemical Society. (f) Diagrammatic representation of the process used to fabricate 2D Co/Fe-BDC with ultrathin nanosheets, electrochemical performance of Co/Fe-BDC electrodes; (g) first cycle's GCD profiles; (h) rate performance at different current densities from 0.1 to 5 A g−1; (i) corresponding GCD profiles at different rates of Co4Fe-BDC electrode. Reproduced with permission from ref. 246, Copyright 2022 Elsevier. |
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Fig. 17 (a) Preparation process for BTCC; (b) SEM images of Zn-BTC; (c) images of the ZnO/C composite; (d) adsorption–desorption isotherm for nitrogen; (e) distribution of pore sizes for BTCC and ZnO/C. Reproduced with permission from ref. 249, Copyright 2022 Elsevier. (f) Distribution of pore sizes in ZnO/C and BTCC; (g) N2 isotherms for adsorption and desorption; (h) PSD curves of PHCNT-1, PHCNT-2, PHCNT-3, and PHCNT-4. (i) SEM of PHCNT-4 before cycling in the SC; (j) SEM of PHCNT-4 after cycling in the SC. Reproduced with permission from ref. 251, Copyright 2024 Wiley. |
Song et al. reported the fabrication of tunable porous hollow carbon nanotubes (PHCNT-x) using InZn-MIL-68. Higher Zn concentrations result in improved characteristics for PHCNT-4 material.251 Hollow carbon nanotubes (CNTs) provide several times the capacity and rate performance of conventional CNTs for storing Na+ ions. They also exhibit exceptional cycle stability and a very high specific capacitance. Fig. 17f–h shows the PSD curves and the pore-size distribution. The redesigned PHCNT-4 electrode's hollow structure and appropriate microporous/mesoporous content allow SCs and SIBs to have the following specific capacitance and rate capability: at 0.1 A g−1 and 1 A g−1 current densities, respectively, the specific capacitance approaches 358.6 F g−1 and 318.2 mAh g−1. The remarkable stability of PHCNT-4 is further supported by Fig. 17i and j, which shows that after cycle testing, the material's morphology virtually remains the same with just a minor increase in oxygen concentration.
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Fig. 18 (a) Illustration of the synthesis of ZIF-8, NC, ZIF-67, GC, ZIF-8@ZIF-67 and NC @GC; (b) NC@GC SEM image; (c) NC@GC TEM image; and (d) NC@GC high-resolution TEM picture. Reproduced with permission from ref. 254, Copyright 2016 Elsevier. (e) Illustration of the procedures used to synthesize ZIF-8@ZIF-67 and NC@GC; (f) CoP@Fe-CoP/NC/NF SEM picture; (g and h) CoP@Fe-CoP/NC TEM images. Reproduced with permission from ref. 260, Copyright 2022 American Chemical Society. |
To produce arrays of CoP@Fe-CoP core–shelled nanorods grown on Ni foam doped with nitrogen (CoP@Fe-CoP/NC/NF), Mei et al. reported the phosphorylation of the ZIF-67@Co-Fe Prussian blue analogue (ZIF-67@CoFe-PBA) (Fig. 18e).260 By optimizing the active sites and providing a favorable capability for mass/electron transfer, the core–shelled structure and hierarchical nanorod arrays increase the electrochemically active surface area. Multiple nanoparticles are uniformly distributed over the core–shelled structure of CoP@Fe-CoP/NC. The structure of the chromatophore is a core–shelled naked type with a thin shell but a relatively massive core (Fig. 18f). At the edge of the nanoparticles, amorphous carbon layers are visible (Fig. 18g and h). Numerous micropores were found in the carbon layer formed in situ by the MOF precursor calculation, which may have been caused by the emission of gases (CO2, H2O) during the calcination process. Reactants may reach the inner active sites of CoP@Fe-CoP/NC because of the high porosity of the carbon layer, and the reaction products are gaseous byproducts of electrocatalytic reactions. The previously stated enhanced morphological and chemical compositions allow the self-supported CoP@Fe-CoP/NC/NF heterostructure to create alkaline hydrogen and oxygen with overpotentials of 97 and 270 mV, respectively, producing 100 mA cm−2.
Several techniques, including electrospinning and the template approach, can be used to create one-dimensional fibrous carbon materials with special structural benefits for lithium-ion battery applications, supercapacitors, and other areas.261–263 In 2017, Wang et al.254 proposed the idea of synthesizing ZIF-8/PAN nanofibers by electrospinning and further carbonizing them into one-dimensional nanoporous carbon fibers. The prepared nitrogen-doped MOF layered carbon fiber material (NPCF) exhibits better electrochemical performance than other nitrogen-doped carbon materials when used as supercapacitor electrode materials. Zhu et al.264 used electrospinning to incorporate Sn-MOF precursors into one-dimensional carbon nanofibers and further calcined them to obtain hierarchical porous Sn@C@CNF materials, which worked effectively as negative electrode materials for batteries that include lithium and sodium ions. Xu et al. used lamellar ZIF-67 as a precursor and a simple hydrothermal process and calcination to successfully create nanoflower structures of Mo-doped NiCo-LDH (Fig. 19a).265 NiCo-LDH's distinctive multilevel nanoflower-like structure was preserved by the researcher by varying the Mo doping concentration (Fig. 19b–d). Furthermore, Fig. 19e–g shows the HRTEM and SAED patterns of 0.075 Mo-NiCo-LDH@C, analyzing the shift in NiCo-TEM's electronic structure where the emergence of an amorphous phase was observed. LDH, the dopant Mo sped up the kinetics of charge storage and reduced the volume change. The 0.075 Mo-doped NiCo-LDH demonstrated an A g−1 of 1, a specific capacitance of 1368.4 C g−1, and an 88.4% capacity retention at 10 A g−1. Recently, Zhang et al.266 reported a highly dispersed Co nanoparticle-anchored hierarchical porous N-doped carbon fiber (Co@N-HPCFs) assembled from hollow polyhedrons derived from core–shell MOFs (Fig. 19h). The MOFs/PAN nanofibers were prepared by electrospinning. SEM, TEM and HRTEM images of Co@N-HPCF-800 are shown in Fig. 19i–n. This intricate carbon fiber construction with multi-level porosity can efficiently increase active site exposure and facilitate mass and electron transfer. The produced Co@N-HPCF catalysts, in particular, have significant promise for usage in wearable and portable energy devices and perform well as air cathodes in Zn–air batteries, both in liquid and solid-state.
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Fig. 19 (a) Mo-NiCo-LDH@C synthesis method; (b–d) ZIF-67, Co@C, and 0.075 Mo-NiCo-LDH@C SEM images, respectively; (e) 0.075 Mo-NiCo-LDH@C TEM image; (f) 0.075 Mo-NiCo-LDH@C HRTEM picture; and (g) Mo-NiCo-LDH@C 0.075 SAED pattern. Reproduced with permission from ref. 265, Copyright 2024 Elsevier. (h) Diagrammatic representation of the Co@N-HPCFs catalyst preparation process; (i–k) PAN nanofibers, MOFs/PAN nanofibers, and Co@N-HPCF-800 SEM images; (l–n) Co@N-HPCF-800 TEM and HRTEM images. Reproduced with permission from ref. 266, Copyright 2023, Elsevier. |
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Fig. 20 (a) Synthesis of NiCo@HCS; SEM of (b) Ni@CS and (e) NiCo@HCS (c and f) TEM images and (d and g) HRTEM images of Ni@CS. Reproduced with permission from ref. 268, Copyright 2023 American Chemical Society. (h) Diagram for the production of flower-shaped microporous carbon nanosheets doped with nitrogen (FMNCN-n), flowerlike Zn-TDPAT, and their S/FMNCN-n (n a = 800, 900, and 1000) composites; (i) Zn-TDPAT nanosheet in a flower-like pattern; (j) microporous nitrogen-doped carbon nanosheets with flower-like morphology at 900 °C produced from Zn-TDPAT nanosheets (FMNCN-900); (k) FMNCN TEM pictures; (l) S/MPNCN-900 TEM pictures. Reproduced with permission from ref. 271, Copyright 2018 American Chemical Society. |
Hong et al.271 prepared nitrogen-doped carbon MOF materials (Zn-TDPAT) with petal-like nanosheet structures (Fig. 20h). SEM of the flowerlike nanosheet and the TEM images are shown in Fig. 20i–l. To inhibit the production of polysulfides, three flower-shaped microporous nitrogen-doped carbon nanosheets with pore widths <0.6 nm effectively retained metastable small sulfur molecules (S 2–4). Qian et al. created porous carbon materials that self-dope with inexpensive cobalt (Co-SCPC) to produce spherical, daisy-like structures for use in lithium–sulfur batteries using PVP as a template and carbonizing MOFs at high temperature in an inert environment.272 It exhibits outstanding electrochemical performance and is capable of efficiently inhibiting polysulfides. It has exceptional cycle stability at 1C for 1500 cycles and 5C for 500 cycles. It exhibits high discharge capacities of 1292.5, 992.7, and 495.6 mAh g−1 at higher discharge current rates of 0.1C, 1.0C, and 5.0C, respectively.
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Fig. 21 (a) Schematic representation of the Co3O4/C hierarchical yolk–shell; (b) ZIF-67 dodecahedrons as synthesized in SEM images; and (c and d) ZIF-67/C yolk–shell SEM images of decahedrons. Reproduced with permission from ref. 280, Copyright 2017 Springer. (e) Diagrammatic representation of the synthesis of rGO@CoSx and CoSx-rGO-CoSx composites; (f–i) SEM pictures of the composites as they were synthesized: ZIF/GO/ZIF, CoSx-rGO-CoSx, GO@ZIF and rGO@CoSx respectively; (j) TEM image of the as-synthesized CoSx-rGO-CoSx composites. Reproduced with permission from ref. 283, Copyright 2016 Wiley. |
The preparation of metal–sulfide-related composite materials based on original MOFs is also very popular. Some studies have reported that they are better than oxides in terms of lithium storage capacity. The preparation methods include one-step and step-by-step sulfurization methods. In the selection of sulfide precursors, the ZIF and MIL series are often used. While providing the corresponding metal elements, it is easy to maintain the structure and further sulfurize. Yin et al. developed CoSx@rGO composite materials (Fig. 21e) based on the formation of ZIF-67 on the surface of GO and subsequent sulfurization. These materials were then used as negative electrode materials in lithium-ion batteries.283 Even after the high-temperature sulfurization procedure, the CoSx particles maintained the rhombic dodecahedron shape of the MOF precursor, as seen in Fig. 21f–i. Remarkably, a large number of sulfur granules adorn the coarse-surfaced CoSx-rGO-CoSx composites. Furthermore, the ZIF-67 morphology was preserved by ZIF/GO/ZIF, CoSx-rGO-CoSx, GO@ZIF, and rGO@CoSx. The CoSx-rGO-CoSx composites' TEM observation (Fig. 21j) shows that they are porous and homogenous as produced. The distribution of CoSx on both sides of GO was demonstrated for particles with varying depths. The as-prepared CoSx-rGO-CoSx and rGO@CoSx composites as LIB anode materials demonstrated exceptional rate capabilities and electrochemical performances. With a current density of 100 mA g−1 and a high initial specific capacity of 1248 and 1320 mAh g−1, the electrochemical performance exhibited 100 stable cycles at 670 and 613 mAh g−1, respectively. Chen et al.284 prepared various sulfonate-derived MOFs as precursors using 4,4′-bipyridine and 1,5-naphthalene disulfonic acid as organic ligands. Together with 4,4′-bipyridine, 1,5-naphthalene disulfonic acid may also provide N/S co-doped carbon molecules and act as a sulfur source for in situ sulfurization during the ensuing pyrolysis process. Among them, Fe7S8/NSC materials exhibit superior electrochemical performance when used as sodium- and lithium-ion negative electrode materials. Because of their excellent conductivity and stability, metal phosphides generated from MOFs can be used in the energy storage industry.285,286 By altering the proportion of Co(NO3)2·6H2O and 2-methylimidazole, Liu et al. produced nanoscale cobalt phosphide S-CoP/CNT composites obtained from ZIF-67 and further phosphated them. They helped to improve the electrochemical performance of the battery when used in lithium–sulfur battery separators by increasing the polysulfide adsorption capacity.287 Researchers have discovered that doping phosphides into materials formed from MOFs is a successful strategy for enhancing electrochemical performance in addition to in situ phosphating. For lithium–sulfur batteries, it serves as a positive electrode material; Chen et al. synthesized Zn@NPC-Ni12P5-CNT-n, a Ni12P5-doped dual carbon material (nitrogen-doped carbon, carbon nanotubes). According to a study, doping with N12P5 enhanced the stability, aided in the quick diffusion of lithium ions, and expanded the number of active sites for trapping polysulfides.288
By employing a one-step calcination process to develop a bimetallic Ni/Co Prussian blue analog, NiCo-PBA, as a precursor, Zhao et al. produced a carbon-doped NiO@Co3O4 composite material.290 As an electrode material for supercapacitors, this composite material may deliver a high energy density of 32.6 Wh kg−1 at a power density of 750.0 W kg−1, with an 87.1% cycle life after 5000 cycles. Li et al. recently produced NiCo2O4/carbon composite nanofibers by securing NiCo2O4 particles obtained from MOFs on highly conductive carbon nanofibers (Fig. 22a).291 Fig. 22b–f show SEM and TEM images of the beaded NiCo2O4/carbon composite nanofibers that were created by growing MOFs in situ on electrospun nanofibers (ZIF-67 was used as the template) and then annealing. When employed as a negative electrode in batteries containing lithium and sodium ions, these nanofibers exhibit remarkable performance.
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Fig. 22 (a) Illustration of creating porous MOFs using carbon/NiCo2O4 composite nanofibers; (b–e) PAN/Ni-7, ZPN-7, ZPN-12, and NCO/C-18 SEM images; (f) TEM image of the NCO/C-12. Reproduced with permission from ref. 291, Copyright 2023 Elsevier. (g) Composition of NZMO QD@C schematic diagram: (a) Ni-Mn-MIL-100 precursor synthesis; (b) gradient calcination procedure; (c) electrochemical induction in situ. Reproduced with permission from ref. 292, Copyright 2024, Elsevier. |
The electrospun PAN/Ni-7 nanofibers made contact with each other in parallel rather than crossing, and their smooth surfaces had an average diameter of 60 nm. Several large ZIF-67 crystals (more than 1 μm) with a rhombic dodecahedron shape were randomly arranged on the nanofiber after in situ formation. This type of nickel–cobalt bimetallic oxide-doped carbon material is simple to synthesize and provides new ideas for multi-metal oxide-doped carbon materials. Using Mn-MIL-100 as the precursor, Ma and associates employed an electrochemical induction technique to gradiently calcine Ni-doped ZnMn2O4 quantum dots (NZMO QD@C) made of carbon layers (Fig. 22g).292 ZnMn2O4 has more active sites and shorter Zn2+ diffusion paths due to the existence of a 0D quantum dot structure. Ni doping can improve conductivity, promote electron rearrangement, and ultimately improve the electrochemical performance and reaction kinetics of cathode materials. Moreover, Ni doping effectively strengthens the Mn–O bond in NZMO QD@C by changing the Mn ion state and the electrical bandgap. Thus, the synthesized cathode showed greater discharge capabilities of 392 mAh g−1 at 0.1 A g−1 and capacity retention of around 82.28 percent of initial capacity for more than 820 cycles at 1 A g−1 when compared to the original MO QD@C cathode.
Multi-metal sulfides and phosphides based on MOFs have also been the subject of intense research in recent years. Sun and associates developed the sulfur-doped carbon-coated FeS2/ZnS hollowed layered spherical material Fe-Zn-S@S-doped-C by synthesizing Fe/Zn-MOF-74 precursors by coprecipitation and sulfurization.293 Its capacity as a negative electrode material for lithium-ion batteries was 679 mAh g−1 at 1 A g−1. However, even after 200 cycles, the electrode's original capacity of 1321 mAh g−1 could be maintained, surpassing it. Following the synthesis of the CoZn-MOFs precursor, Fang et al. employed calcination and sulfurization to produce bimetallic sulfide (Co9S8/ZnS) nanocrystals embedded in nitrogen-doped hollow carbon nanosheets.294 After optimization, Co1Zn1-S (600), calcined at 600 °C, was selected. When used as anode materials for half-cell and full-cell Na3V2(PO4)3‖Co1Zn1-S (600) sodium-ion batteries, it showed outstanding rate performance and cycle stability. Dai et al. created a precursor of bimetallic Ni-Sn-BTC MOF using microwave-assisted solvothermal and cation exchange methods.295 A C2H2/Ar environment was then used to calcine and phosphate it to create Ni-Sn-P@C-CNT derivative materials. When used as anode materials in lithium-ion batteries, the two electrochemical components and in situ carbon nanotubes (CNTs) exhibit faster ion movement and enhanced cycle stability. Following the successful creation of nickel and cobalt bimetallic compound electrode materials, Ni et al. recently incorporated manganese metal to enhance the electrochemical performance by better activating the 3d electrons of cobalt ions.296 When applied to supercapacitor electrode materials, a double-layer hollow cage-structured Mn–Ni–Co sulfide composite material was created using ZIF-67 as a template and demonstrated exceptional performance.
Using surface oxygen sites from uncoordinated MOF ligands, Rui et al. reported an effective method for creating a noble metal/2D MOF heterostructure. The incorporation of highly dispersed noble metal nanoparticles (such as Pt and Pd) with a modulated electronic structure was made possible on a MOF surface free of surfactants. As a proof-of-concept demonstration, a 2D Ni-MOF@Pt hybrid with well-defined interfaces was applied to enhance the electrochemical hydrogen evolution reaction (HER) and to provide respectable electrocatalytic activity under both acidic and alkaline conditions.297 Li et al. investigated the hydrogen storage potential of a noble metal/2D MOF heterostructure. Using a wet-chemical process and subsequent heat treatment, Pd metal nanoparticles were anchored on the surface of ultra-thin Ni-MOF nanosheets (Ni-MOF@Pd) and added to MgH2. According to structural study, Mg2Ni/Mg2NiH4 and Mg6Pd species formed in situ facilitate the dehydrogenation of MgH2 and encourage the diffusion and transfer of hydrogen atoms. Because of the nanocomposite's amorphous C structure, which legitimately inhibits particle agglomeration, the system also exhibits sustained cyclic dynamics during 10 times high-rate de/hydrogenation.298
(1) Pure MOF materials are easy to composite and modify and subsequently process to prepare derivative materials to enhance electrochemical performance. However, there are still many issues that need to be resolved in real-world applications, such as the search for affordable and eco-friendly raw materials and straightforward synthesis techniques.
(2) When applied to alkali metal batteries, MOFs are used as negative electrode materials and combined with bimetallic synergy, precursor carbonization, macroscopic structure design, introduction of microscopic defects and other modification measures to effectively improve the capacity and rate performance. However, compared with LIBs, research on MOF-based negative electrode materials for SIBs and PIBs is not extensive. The large ionic radius of sodium and potassium cause slow insertion and extraction kinetics, resulting in poor performance. Consequently, the next line of study for the use of materials produced from MOFs in the negative electrode materials of alkali-metal-ion batteries is controlling the right pore size to guarantee kinetics with both high conductivity and stability.
(3) The design of unsaturated MOFs, Lewis acid sites, and the selection of organic ligands containing nitrogen, oxygen, and phosphorus functional groups in metal–sulfur batteries have significant effects on improving sulfur carriers and polysulfide capture. Compared with MOF coatings, MOF materials have problems such as insufficient screening ability and weak stability when preparing LSBs-modified diaphragms.
(4) There are few reports on the ultra-long cycle stability of MOF materials in various secondary batteries and supercapacitor applications. At present, MOF-derived materials are emerging in an endless stream, but their preparation schemes are becoming increasingly complicated, and structural collapse problems often occur during the preparation process. It is urgent to explore a material preparation strategy with a simple preparation process and safe and stable.
Future studies and modifications can be conducted from the following angles to achieve the large-scale use of MOF-related materials in energy storage:
(1) When creating materials changed by MOFs, the microstructure should be controlled naturally. Considerable advancements have been achieved in the energy storage sector using the principle of coordination unsaturation. The electrochemical performance of MOF materials can be further enhanced by the addition of unsaturated metal nodes and the regulatory approach between organic ligands in the structure. The introduction of low-dimensional vacancy defects can also enhance the conductivity of MOF materials.
(2) Mass and charge transfer are accelerated by the profusion of active sites, and the short-range order characteristics can provide a suitable pore environment to reduce the volume expansion problem. Introducing MOFs into various energy storage devices will help provide more control strategies for the material in terms of microstructure, thereby compensating for the shortcomings in the application of original crystalline MOF materials.
(3) Modification of MOF-derived materials by multi-metal doping should be considered. Based on the mechanism that multi-metal active centers expose more active sites, increase ion reaction potential, and enhance electrochemical performance through the synergistic effect of multiple electrochemically active components, multi-metal doping derived from pure MOFs (ZIF, MIL, etc.) is very effective. Compared with transition metal- and precious metal-based materials commonly used in batteries and electrocatalysts, elements such as iron, cobalt, nickel, and manganese are more abundant in the earth's crust, safer and more environmentally friendly.
(4) Enhancing the crystal structure and morphogenesis and creating more structural composites are two ways to further improve the electrochemical properties of materials developed from MOFs. In addition, heterogeneous structures such as MOF-on-MOF can integrate advantageous components to produce synergistic effects. These innovative structural designs will provide new opportunities for the optimization of MOF materials used for energy storage purposes. It is expected that further modified MOF materials with improved electrochemical performance will be developed.
In summary, MOF materials and their derivatives show enormous promise for the energy storage industry. MOF materials will also be more suited for use in energy storage devices thanks to the performance regulation technique and composite material production. To overcome these limitations in the research of MOFs and their derivatives in the energy storage industry, this article provides a quick overview of the existing research on MOF materials.
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