Sequential anaerobic-aerobic photocatalytic degradation of halogenated organic pollutants via dual-site confined carbon nitride.

Solar-driven photocatalytic dehalogenation and mineralization of halogenated organic pollutants (HOPs) remain a significant challenge. In this study, we develop a dual-site confined g-CN (CN)-based catalyst, incorporating cerium doping and nitrogen vacancies (Ce-FCNV), for a sequential anaerobic-aerobic photocatalytic system designed for the deep treatment of HOPs-contaminated wastewater. The Ce-FCNV catalyst demonstrates a remarkable 36.04-fold increase in photocatalytic activity for 4-chlorophenol (4-CP) degradation compared to pristine CN. Notably, it achieves near-complete dechlorination (99.45 %) and mineralization (99.21 %) efficiencies in the anaerobic-aerobic system, significantly outperforming single-aerobic, single-anaerobic, and combined aerobic-anaerobic systems. Kinetic and mechanistic studies reveal that the dual catalytic sites and pore confinement effects of Ce-FCNV enhance the generation of reactive species (e.g., •OH, •O⁻, and electrons) and accelerate 4-CP degradation. Experimental and computational analyses further indicate that the dual-sites lower the C-Cl bond dissociation energy, promote •OH generation, and improve carrier separation. The system exhibits broad applicability, effectively degrading various HOPs and adapting to diverse water matrices, even in real occurrence ranges. This work highlights a novel strategy leveraging the synergistic effects of dual sites within a multi-level pore structure of CN, offering a promising approach for the efficient purification of HOPs-contaminated wastewater in anaerobic-aerobic photocatalytic systems.