A Systematic Research on the Synthesis, Structures, and Application in Photocatalysis of Cluster-Based Coordination Complexes

To search for effective photocatalysts in the field of cluster-based coordination complexes, we synthesized {[Cd2­(dcpp)­(beb)2 (H2O)]·H2O}n (1), [Cd2­(dcpp)­(bmb)­(H2O)2]n (2), {[Cd2­(dcpp)­(2,2′-bipy)­(H2O)2]·2H2O}n (3), and {[Cd2­(dcpp)­(4,4′-bipy)0.5­(H2O)3]·H2O}n (4) by utilizing a butterfly-shaped multidentate carboxylic acid (4,5-di­(4′-carboxyl­phenyl)­phthalic acid) (H4dcpp)) and N-donor ligands (1,4-bis­(2-ethyl­benz­imidazol-1-ylmethyl) benzene (beb), 1,4-bis­(2-methyl­benz­imidazol-1-ylmethyl) benzene (bmb), 2,2′-bipyridine (2,2′-bipy), 4,4′-bipyridine (4,4′-bipy)). Complexes 1–4 are constructed based on different SBUs. Complexes 1 and 2 possess three-dimensional (3D) pillar-layered frameworks based on noncluster-type SBUs and dinuclear Cd2 clusters units, respectively. Complex 3 is a 3D porous structure building on Cd4 clusters SBUs. Complex 4 is constructed from rare infinite botryoid-like Cd cluster chains and exhibits a 3D complicated framework. The research on optical energy gaps of complexes 1–4 indicates that these complexes are potential semiconductive materials. Moreover, complexes 1–4 are applied to catalyze the reaction of photocatalytic degradation of methylene orange (MO) under high-pressure mercury lamp irradiation. Excitingly, they exhibit good photocatalytic properties in the presence of H2O2, and the degradation rates for 1–4 increase from 43% (without photocatalyst) to 97, 78, 85, and 67%, respectively, after 100 min of irradiation. The photoluminescent properties of complexes 1–4 were also studied.