Syntheses, structures, magnetism and photocatalytic degradation of methylene blue dye of two copper complexes based on a semirigid tricarboxylate ligand

Two Cu(II)-complexes [Cu(Hcpota)(4,4′-bpy)(H2O)]n 1 and [Cu(Hcpota)(1,4-bib)(H2O)]n 2 based on a semirigid ligand 2-(4-carboxyphenoxy)terephthalic acid (H3cpota) were solvothermally prepared and characterized. Complexes 1 and 2 exhibit an unprecedented 2D 4-connected framework with a {44.62} topology, comprising the Cu(II) ion with square pyramidal coordination. The three-dimensional frameworks are constructed by O–H···O hydrogen bonds. Magnetization analyses were conducted and revealed that complexes 1 and 2 have ferromagnetic properties. The photodegradation of Methylene blue dye was studied based on 1 and 2 as photocatalysts. The results indicated that complexes 1 and 2 exhibited remarkable photodegradation efficiencies of 86.9% and 97.0% after 24 minutes, respectively. Furthermore, pseudo-first-order kinetics was assumed for the photocatalytic reaction with a rate constant of 0.052 and 0.109 min−1 for 1 and 2. The impact of factors, including the initial concentration of MB, catalyst dosage, pH value, H2O2 concentration, and temperature on the degradation process of MB was thoroughly examined. The complexes exhibited excellent recyclability and stability as photocatalysts. Trapping experiments and LC-MS studies revealed that the primary active species responsible for the degradation reaction are hydroxyl radicals (·OH) and holes (h+).