Metal Center-Tuned Photocatalytic Carbon Dioxide Reduction for Frameworks with the Tetraphenylethene–Imidazole Ligand

As heterogeneous photocatalysts that can effectively transform CO₂ to CO, two MOFs with different metal centers, namely, [M(tipe)(H₂O)₂](ClO₄)₂·solvent (M = Ni named as Ni-MOF and M = Co referred to as Co-MOF), were synthesized by reactions of 1,1,2,2-tetrakis(4-(imidazole-1-yl)phenyl)ethene (tipe) with the corresponding metal perchlorate. Both Ni-MOF and Co-MOF have 3D structures, in which the metal centers have the same coordination environment with the N₄O₂ donor set. Driven by visible light, the CO production catalyzed by Co-MOF is 6734.1 μmol g^-1 with 45.3% selectivity, and in contrast, Ni-MOF has 4601.3 μmol g^-1 CO production with 97.6% selectivity in 5 h. Through photoelectrochemical characterization, DFT calculations, and in situ FT-IR measurements, the photocatalytic CO₂ reduction process catalyzed by Ni-MOF and Co-MOF was investigated. The results show that the metal center of the MOF is crucial for photocatalytic CO₂ reduction. This work offers an innovative approach for controlling the performance of photocatalytic CO₂ reduction through tuning the metal centers of architectures.