Interface-coupled supramolecular self-assembly 2D Z-scheme TiO2/g-C3N4 heterojunction for efficient degradation of tetracycline under visible light

Tetracycline (TC), a widely used antibiotics, poses environmental risks due to its persistence and bioaccumulation potential. Visible light photocatalysis has emerged as a promising technique for TC degradation. In this study, a supramolecular self-assembled TiO2/g-C3N4 (S-TCN) heterojunction and a weakly mixed TiO2/g- C3N4 (W-TCN) were synthesized via a one-pot method to elucidate the impact of interfacial coupling strength on photocatalytic performance. The results demonstrated that S-TCN, with robust Ti-O-C and N-O-Ti bonds, exhibited enhanced interfacial coupling, reduced interfacial resistance, and increased photocurrent density, improving electron transfer and carrier separation. Under simulated visible light, S-TCN achieved superior TC degradation efficiency (85.0 % within 60 min), outperforming W-TCN and previously reported photocatalysts. Radical scavenging and EPR analyses confirmed center dot O2- as the primary active species, with additional contributions from h+, e-, center dot OH, validating the Z-scheme charge transfer mechanism. UPLC/Q-TOF MS analysis revealed four major TC degradation pathways, including hydroxylation, demethylation, and ring-opening reactions, ultimately mineralizing. Environmental factor assessments demonstrated S-TCN's stable performance across various conditions. This study highlights the critical role of interfacial coupling in photocatalysis and underscores the potential of supramolecular self-assembly in designing advanced photocatalysts for wastewater treatment, providing valuable theoretical and practical insights.