Base-mediated exfoliation of quinoline-linked covalent organic frameworks for heavy metal ion adsorption†
Abstract
Multicomponent reactions that combine sequential reversible and irreversible bond forming reactions are efficient methods for the synthesis of robust covalent organic frameworks (COFs) with high crystallinity and stability. Here, we report a mild synthetic method for the synthesis of quinoline-linked covalent organic frameworks (Qu-COFs) using a multicomponent Doebner reaction. These Qu-COFs have high stability, crystallinity, porosity, and good wettability. The unique quinoline-4-carboxylic acid linkage resulting from the Doebner reaction enables ion insertion and exfoliation of bulk Qu-COF under mild conditions to give 2D nanosheets (Qu-CONs). Furthermore, the exfoliated Qu-CONs exhibit ultrafast cadmium ion uptake. Our work provides a mild and efficient method for synthesizing stable, functionally diverse 2D nanosheets and further expands the potential applications of COFs.