The photocatalytic performance on d-block metal complexes with unsaturated coordination circumstances after one dative-bond cleavage has becoming an emerging domain. Especially, photocatalytic CO2 reduction reaction (CO2RR) on active center of d-block metals in tridentate/bidentate ligands with square pyramidal nitrogen-coordinated atoms has been reported. In this study, photocatalytic CO2RR performance on the screened-out six metals in [TM(tpy)(ppy)]0 active species (TM = Fe, Co, Ru, Rh, Re, and Ir) for CO production were evaluated in details using DFT computations. The theoretical data demonstrate that the [Re(tpy)(ppy)]0 exhibits superior photocatalytic CO2RR activity than other identical species, with the one-electron photoreduction step as its lowest rate-limiting step of 38.41 kcal mol-1. Besides, the initial adsorption of CO2 on [Re(tpy)(ppy)]0 is more favorable with the ΔG of -4.30 kcal mol-1 due to the unique matching among the fragments’ FMOs of Re and CO2. In addition, our calculations reveal that the electron-transfer processes along the CO2RR pathway on [TM(tpy)(ppy)]0 are mainly sourced from the tpy ligand. Therefore, our study paves the way to explore the active species of metal complexes as photocatalysis on CO2RR before executing the targeted experimental exploration on their precursor complexes to discover the qualified ones.
