Ligand-induced synthesis of two Cu-based coordination polymers and derivation of carbon-coated metal oxide heterojunctions for enhanced photocatalytic degradation

Abstract

Photocatalytic degradation of dyes is an extremely difficult but very important issue in the field of environmental protection. Two coordination polymers (CPs) [Cu(3-bpah)(HD)]_n (1) and [Cu(3-dpye)_0.5(HD)]_n (2) [3-bpah = N,N’-bis(3-pyridinecarboxamide)-1,2-cyclohexane, 3-dpye = N,N’-bis(3-pyridinecarboxamide)-1,2-ethane, H₂HD = hexanedioic acid] were successfully synthesized by tuning the auxiliary ligands under hydrothermal conditions. CPs 1 and 2 exhibited different compositions because of the different N-donor ligands, and were used as precursors for the preparation of metal oxide heterojunctions. Doping foreign elements into intrinsic CP-based materials is an effective way to enhance their photocatalytic activity, and thus we designed a facile method to synthesize a series of carbon-coated metal oxide heterojunctions which were derived from the two Cu-based CPs (Cu@V-1, Cu@V-2, Cu@Mo-1, Cu@Mo-2, Cu@W-1 and Cu@W-2) in this work for the first time. Benefiting from the formation of a carbon shell and regulation of the electronic structure through doping molybdenum and generating the Mo₂C phase, the photocatalytic degradation rates were 94.84% for MB, 76.02% for RhB, 52.29% for MO, and 86.18% for CR after 4 h.