Visible-Light-Driven Photocatalysts of Metal-Organic Frameworks Derived from Multi-Carboxylic Acid and Imidazole-Based Spacer

Five new metal organic frameworks [M-(btec)(0.5)(bimb)](n) (1) (M = Co (1), Ni (2), Cu (3), Zn (4)) and [Cd(btec)(0.5)(bimb)(0.5)](n) (5), were obtained by reactions of the conjugated 1,2,4,5-benzenetetracarboxylic acid (H(4)btec) and 4,4'-bis(1-imidazolyl)biphenyl (bimb) with corresponding metal salts under hydrothermal conditions, respectively. MOFs 1-5 show different structures and topologies: compounds 1 and 4 are isomorphic, which possess typical PtS 3D nets; compound 2, 3 and 5 exhibit 2D layer structure, NbO 3D network and (4,6)-connected 3D binodal topology, respectively. Notably, compounds 1, 2, and 5 represent the rare example of MOFs-based visible-light-driven photocatalysts and show good stability toward photocatalysis. Furthermore, compound 5 is photocatalytically more active than 1 and 2 because of the relatively narrower band gap calculated from LMCT transitions. In addition, the formation rate of center dot OH radicals on compound 5/H2O interface via photocatalytic reactions is much higher than that of 1 and 2, implying that the formation rate of center dot OH radicals during photocatalysis is in agreement with photocatalytic activity and the formation rate of center dot OH radicals is an important factor influencing photocatalytic performance.