Stable cuprous active sites in Cu-graphitic carbon nitride: Structure analysis and performance in Fenton-like reactions.

Cu-based catalysts have great potential in Fenton reactions under neutral pH conditions. However, cuprous (Cu) materials are instable in the aqueous environment. Herein, using the cheap precursors, a Cu-graphitic carbon nitride complex with an efficient Fenton-like activity as well as relative stability was prepared. 99.2% removal of Rhodamine B with an initial concentration of 50 mg/L could be attained in 1 h. Several experimental techniques are employed to study the structure of this catalyst. Results show that after the addition of Cu, the graphitic carbon nitride (g-CN) network is partially destroyed and the reduced Cu is therefore firmly embedded in the fragmentary g-CN sheet. The X-ray adsorption fine spectra illustrates the chemical state and the local structure of the bonded Cu. Due to the strong orbital hybridization, Cu could be stabilized through the coordination with pyridinic N. A two-coordinate structure with a bond length of 1.90 Å is confirmed and this structure is not changed even after the Fenton-like reaction. Singlet oxygen (O) and hydroxyl radicals (HO•) are produced by the rapid interaction of bonded Cu with HO and the resulting Cu can be easily reduced to its cuprous state due to its structure stability, leading to its high activity in the Fenton-like reaction.