Regulating the local electron density and adsorption energy of COF-based single copper sites for highly efficient Fenton-like photo-oxidation

Highly efficient single-atom catalysts (SACs) hold great potential for promoting peroxymonosulfate (PMS) activation to facilitate organic pollutant degradation but precisely regulating and enhancing their catalytic efficiency remains a challenge. Here, single Cu atom catalysts anchored on a series of ketoenamine-based covalent organic frameworks (COFs) were developed as PMS activators via a facile dielectric barrier discharge (DBD) plasma and wet chemical method. Based on the systematic engineering of photoelectric structures at the molecular level, the charge distribution was precisely regulated by introducing different functional groups (Cu@TpPa-X, where X= -(CH), -H, -CN). Among the obtained materials, Cu@TpPa-(CH) possesses the best photocatalytic capability, and the mineralization (90%) of carbamazepine (CBZ) and the reaction rate constant (0.322 min) are comparable to those of the most advanced photocatalysts. Experiments and calculations demonstrate that the introduction of individual metal atoms increases the electron density at the active centre, and electron-donating groups accelerate the transfer of photogenerated carriers and improve the PMS adsorption to the material, which significantly improves the overall oxidation and mineralization kinetics. This work pioneers a novel approach for tailoring high-efficiency COF-based SACs, thus broadening their potential applications in photocatalysis.