Crystalline Covalent Organic Frameworks Based on Mixed Metallo- and Tetrahydroporphyrin Monomers for Use as Efficient Photocatalysts in Dye Pollutant Removal

Unique features, including a high specific surface area, great stability, and crystallinity, make covalent organic frameworks (COFs) intriguing sorbents and catalysts in light-driven water pollutant degradation. Inspired by the light absorption capability of porphyrin derivatives and the carrier separation ability of a donor-acceptor (D-A) configuration, we constructed two-dimensional porphyrin donor-based D-A COFs: COF-HTBD involving only tetrahydroporphyrins and COF-HMTBD (M = Co, Fe, Cu) involving both tetrahydro- and metalloporphyrins via a mixed porphyrin monomer strategy. The monomer 2,1,3-benzothiadiazole-4,7dicarboxaldehyde (BD) is incorporated as an electron accepting moiety. Interestingly, COF-HTBD, COF-HCuTBD, and COF-HFeTBD exhibit staggered stacking, while the stacking model of COF-HCoTBD transforms from staggered to eclipsed. Notably, COF-HFeTBD demonstrates excellent activities and stabilities toward visible light-driven photocatalytic rhodamine B (RhB) degradation in aqueous solutions with H2O2 present (100% removal in 3 h). Overall, this work provides an interesting strategy for the construction of D-A-type porphyrin COFs for dye pollutant removal.