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

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)] (1) and [Cu(3-dpye)(HD)] (2) [3-bpah = ,-bis(3-pyridinecarboxamide)-1,2-cyclohexane, 3-dpye = ,-bis(3-pyridinecarboxamide)-1,2-ethane, HHD = 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 MoC 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.