Synthesis, Structure and Photocatalytic Dye Degradation Ability of Co(II)-Based Coordination Polymers

Two Co(II)-based coordination polymers: {Co(L1)(bimb)·H2O·OH}n (1) and [Co(L2)(bidpe)]n (2) (H2L1 = 4-mercaptobenzoic acid, H2L2 = 4,4′-bis(thiomethylene) dibenzoic acid, bimb = 1,4-bis(imidazol-1-ylmethyl)benzene), bidpe = 4,4′-bis(imidazolyl)diphenyl ether), were synthesized under the condition of solvothermal and characterized by X-ray single-crystal diffraction, elemental analysis, IR spectra and thermogravimetric analysis (TGA). X-ray single-crystal diffraction analysis exhibits that 1 and 2 belong to the monoclinic crystal system, space group P21 and Cc. Complex 1 adopts a tetrahedron {CoN2O2} coordination geometry and complex 2 possesses a distorted trigonal bipyramid {CoN2O3} coordination geometry. Topology analysis results show that complex 1 and 2 possess a uninodal 4-connected 2D (two-dimensional) sql topology framework with the Schläfli symbol (44·62). Furthermore, the photocatalytic degradation property and mechanism of 1 and 2 for methylene blue (MB) were investigated. The results show that the band gap (Eg) of 1–2 is 2.69 eV and 2.60 eV, and the equipotential point (pHpzc) of 1–2 is 4.47 and 4.40. Complex 1–2 show excellent photocatalytic degradation for MB. ·OH is the main active substance causing MB degradation.