Syntheses, structure, photocatalytic degradation for methylene blue of Co(II)-Based coordination polymers

Abstract

Two Co(II)-based coordination polymers: [Co2(L)2(bib)2]n (1) and {[Co2(L)2(bimb)2]·2H2O·DMA)}n (DMA = N,N-dimethylacetamide) (2) using 4,4′-bis(thiomethylene) dibenzoic acid (H2L) as the first ligand, 1,4-bis(imidazol)-butane (bib) and 1,4-bis(imidazol-1-ylmethyl)benzene) (bimb) as the second ligands, 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 triclinic crystal system, space group P-1. The central Co(II) ions exhibit a regular spatial tetrahedral structure which are coordinated by two O atoms from two L2− ligands and two N atoms from two N-donor ligands. Furthermore, the photocatalytic degradation properties and mechanism of 1 and 2 for methylene blue (MB) were investigated. The results show that the band gap (Eg) of 1 and 2 is 3.78 eV and 3.82 eV, and the equipotential point (pHpzc) of 1 is 4.25. Both 1 and 2 show excellent photocatalytic degradation for MB. •OH is the main active substance causing MB degradation. The photocatalytic degradation for MB of 1 and 2 is in line with the first order kinetics equation.