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 {[Cd-2(dcPP)(beb)(2) (H2O)]center dot H2O}(n) (1), [Cd-2(dcpp)(bmb)(H2O)(2)](n) (2), {[Cd-2(dcpp)(2,2'-bipy)(H2O)(2)]center dot 2H(2)O}(n) (3), and {[Cd-2(dcPP)(4,4'-bipy)(0.5)(H2O)(3)]center dot H2O}(n) (4) by utilizing a butterfly-shaped multidentate carboxylic acid (4,5-di(4'-carboxylphenyl)phthalic acid) (H(4)dcpp)) and N-donor ligands (1,4-bis(2-ethylbenzimidazol-1-ylmethyl) benzene (beb), 1,4-bis(2-methylbenz-imidazol-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 Cd-2 clusters units, respectively. Complex 3 is a 3D porous structure building on Cd-4 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.