Visible light-driven selective redirection of phenolic carbon in heterogeneous Fenton-like reaction

Oxidative polymerization of phenolic pollutants by the heterogeneous Fenton-like reaction is a sustainable strategy for wastewater decontamination and recovery of carbonaceous resources. However, controlling the reaction pathway to selectively polymerize the phenolic pollutants is challenging. Herein, we used visible light to shift the reaction pathway from phenolic pollutants degradation (which often results in incomplete mineralization) to polymerization over a g-C₃N₄ catalyst deposited on a Cu₂O nanowire. In peroxymonosulfate (PMS) activation, visible light illumination facilitates electron transfer from Cu₂O to g-C₃N₄, shifting the dominant reactive species on the Cu₂O surface from radical species to catalyst-PMS* complex. Experimental results and theoretical calculations verified the increased adsorption of PMS and the reduced energy barrier for phenol (PhOH) polymerization under visible light illumination. Compared to dark control conditions, visible light-assisted Fenton-like process resulted in a 9-fold faster PhOH oxidation (0.029 min⁻¹), significantly higher PMS utilization efficiency for total organic carbon removal, and enhanced robustness in real water matrices. This study provides fundamental insights into the regulation of reaction pathway over light-responsive semiconductor catalysts and highlights the potential for efficient treatment of phenolic water pollutants via oxidative polymerization.