Photo-Fenton Degradation of Tetracycline Boosted by Charge Redistribution in g-C₃N₄with Fe–N₂Configuration and O/P Dual Doping

The persistent contamination of aquatic environments by tetracycline (TC) necessitates advanced remediation strategies. Herein, a ternary Fe–O–P-co-modified graphitic carbon nitride (FOPCNx) was synthesized via structural integration of Fe–N₂configurations with O/P dual doping for efficient TC degradation in a solar-driven photo-Fenton system. This study pioneers the synergistic coupling of Fe–N₂coordination and heteroatomic O/P substitution to optimize charge dynamics. Comprehensive characterization confirmed the formation of Fe–N₂active sites and aromatic structures incorporated with the aromatic group, which collectively enhanced visible-light absorption, suppressed electron–hole recombination, and facilitated charge carrier redistribution. The optimized FOPCN2 demonstrated exceptional photoelectric efficiency (3.7-fold higher photocurrent density than pristine g-C₃N₄) and achieved 98.9% TC removal within 40 min of irradiation with a kinetic constant of 0.113 min^–1, outperforming conventional systems. Mechanistic studies revealed dual enhancement pathways: Fe–N₂sites promoted electron transfer and Fe(III)/Fe(II) cycling, while the O/P dual doping enabled electron delocalization for improved charge mobility. The system exhibited remarkable pH adaptability (3–7), robust resistance to inorganic anions, and universal degradation capability for mixed organic pollutants. Three TC degradation pathways were identified through intermediate analysis, with radical trapping and EPR verification confirming the dominant roles of^•OH, e^–, and O₂^•–. This work provides critical insights into structure–activity relationships for carbon nitride modification, establishing a paradigm for designing multifunctional photocatalysts for antibiotic-contaminated wastewater remediation.