Solar-driven MOF-derived Co–N–C@TiO₂ direct Z-scheme heterostructure for efficient antibiotic degradation via enhanced interfacial charge transfer

Abstract The development of efficient and sustainable photocatalysts for solar-driven environmental remediation remains an important challenge in the elimination of emerging water contaminants. In this study, a MOF-derived Co–N–C@TiO₂ direct Z-scheme heterostructure was rationally engineered to enhance visible-light utilization and interfacial charge transfer for tetracycline degradation. The composite was synthesized through pyrolysis of a cobalt-based zeolitic imidazolate framework to produce a conductive Co–N–C scaffold, followed by sol–gel deposition of TiO₂ nanoparticles. Structural and physicochemical characterizations (XRD, FTIR, BET, SEM/TEM, XPS, UV–Vis DRS, PL, and Mott–Schottky analyses) confirmed the formation of a porous architecture with a high specific surface area (176.4 m² g⁻¹), uniformly dispersed TiO₂ nanodomains, enhanced visible-light absorption, and efficient suppression of electron–hole recombination. Under visible-light irradiation, the Co–N–C@TiO₂ photocatalyst achieved 93.7 ± 0.8% tetracycline degradation within 60 min, accompanied by a pseudo-first-order rate constant of 0.054 ± 0.001 min⁻¹ and 67.5 ± 2.3% total organic carbon removal, indicating substantial mineralization. The superior photocatalytic performance is attributed to the synergistic interaction between the conductive MOF-derived carbon framework, Co–Nₓ active sites, and the direct Z-scheme heterojunction, which facilitates rapid charge separation while preserving strong redox capability. By efficiently utilizing solar energy for advanced water treatment, this work provides a sustainable photocatalytic strategy that contributes to the United Nations Sustainable Development Goals, particularly SDG 7 (Affordable and Clean Energy) and SDG 13 (Climate Action).