Mechanistic insights and photocatalytic performance of a CCN/Ag3PO4 Z-scheme heterojunction for efficient degradation of chlortetracycline in water

CCN is constructed in a single step via supramolecular self-assembly. • CCN/AP-175 eliminates 96.04% of CTC within 60 min under visible light. • The catalyst exhibits anti-interference capability and robust cyclic stability. • Honeycomb porosity synergizes with the Z-scheme for boosted performance. Conventional g-C 3 N 4 photocatalysts are limited in degrading antibiotics and other micropollutants due to rapid recombination of photogenerated electron–hole pairs. Herein, a highly porous carbon-doped polymeric carbon nitride (CCN) with an super-porous architecture was synthesized via the self-assembly of melamine, cyanuric acid, and barbituric acid, followed by in situ anchoring of Ag 3 PO 4 nanoparticles onto the CCN framework through an ion-exchange precipitation method, yielding a hierarchical porous CCN/ Ag 3 PO 4 (CCN/AP) Z-scheme heterojunction photocatalyst. The optimized CCN/AP-175 achieved 96.04% removal of chlortetracycline (CTC) under visible-light irradiation for 60 min, with a pseudo-first-order rate constant 1.56, 2.23, and 1.55 times higher than those of pristine CCN, pure Ag 3 PO 4 , and conventional nonporous g-C 3 N 4 /Ag 3 PO 4 (CN/AP), respectively. BET, UV–vis diffuse reflectance spectroscopy, photoluminescence, and electrochemical impedance spectroscopy analyses revealed that the hierarchical porosity combined with the Z-scheme heterojunction not only significantly enhanced the specific surface area but also facilitated effective separation and transfer of photogenerated charge carriers. Reactive species trapping experiments and electron spin resonance confirmed that photogenerated holes (h⁺) play a dominant role in CTC degradation. Furthermore, UV–vis DRS and Mott–Schottky measurements corroborated the Z-scheme charge transfer mechanism. Systematic studies of catalyst dosage, initial CTC concentration, solution pH, and coexisting anions demonstrated sustained high degradation performance under diverse conditions. Notably, after four consecutive cycles, the catalyst maintained over 80% removal efficiency with no significant structural deterioration, highlighting its excellent stability. This work offers a viable strategy for designing high-performance porous photocatalysts for practical antibiotic remediation. Download: Download high-res image (233KB) Download: Download full-size image