A dual-reaction-center Fenton-like process on -CN-Cu linkage between copper oxides and defect-containing g-C3N4 for efficient removal of organic pollutants

Copper oxides were supported on the surface of defect-containing g-C3N4 (d-g-C3N4-Cu) by alkalization and hydrothermal methods and characterized using a variety of techniques and density functional theory (DFT) calculations. It was verified that dual reaction centers were constructed by the complexation of -C-1 N-1-Cu linkages between Cu of copper oxides (CuOx) and cyano (-C-1 N-1) groups of the side chain in the tri-s-triazine ring of d-g-C3N4, which formed electron-rich centers around Cu sites and electron-poor centers around C-1 sites. Based on the experimental results, it was established that the Fenton-like process took place with H2O2 being mainly reduced to hydroxyl radicals (OH) by the electrons from electron-rich Cu centers, while both OH- and pollutants were adsorbed on the C-1 sites, and could be oxidized to donate electrons to Cu centers by electron transfer of pi -> Cu in -C-1 N-1-Cu, maintaining charge balance on the d-g-C3N4-Cu. Thus, the catalyst was highly efficient for the degradation of various refractory organic pollutants in water of pH from 3 to 10; moreover, higher pH resulted in higher reaction efficiency because more adsorbed OH- at C-1 sites produced more (OH)-O-center dot. Our findings indicate that the dual-reaction-center Fenton-like process is very promising for environmental remediation.