Synergistic photocatalysis and fenton-like activity in CuS@g-C3N4 heterojunctions for enhanced tetracycline removal from water

Antibiotic contamination, particularly tetracycline (TC), remains a pressing environmental concern. Herein, a three-dimensional flower-like CuS@g-C 3 N 4 heterojunction was developed that couples visible-light photocatalysis with Fenton-like activation of H 2 O 2 , enabling continuous TC degradation under both light and dark conditions. Strong Cu–S–N interfacial bonding and Type-II band alignment facilitate directional charge transfer and suppress carrier recombination, thereby promoting the generation of •OH and •O 2 ⁻ radicals through dual-channel activation. Mechanistically, photo-assisted Cu 2+ /Cu + cycling in CuS catalyzes H 2 O 2 decomposition into reactive oxygen species, while g-C 3 N 4 enhances electron–hole separation and O 2 reduction under illumination. This synergistic coupling achieves over 98% TC removal within 30 min. Structural and spectroscopic analyses, together with EPR and DFT results, confirm that interfacial engineering and band modulation govern carrier dynamics and radical formation, ensuring high activity and stability. This work provides a comprehensive quantitative mechanistic insight into multi-pathway degradation, and delivers a scalable, bifunctional platform for the persistent elimination of antibiotics and emerging contaminants, significantly advancing the field of sustainable environmental water purification. • 3D CuS@g-C 3 N 4 heterojunction enables efficient TC removal in light and dark. • H 2 O 2 activates Cu 2+ /Cu + species to generate •OH and •O 2 − radicals for oxidation. • Type-II band alignment boosts electron–hole separation for ROS generation. • Interfacial interactions, possibly via Cu–N coordination, promote electron transfer.