Engineering MOF-Derived Bi2WO6 via In Situ Bi0 Formation for Plasmonic S-Scheme Bi2WO6/Bi/g-C3N5 Heterostructure for Enhanced Tetracycline Degradation and Toxicity Mitigation.

The efficient removal of antibiotic contaminants from aquatic environments remains a critical challenge due to their persistence and potential ecological risks. In this study, two synthetic strategies were developed to construct Bi2WO6/Bi/g-C3N5 S-scheme heterostructured photocatalysts, enabling a direct comparison between a conventional Bi2WO6 route (BWO-route) and a metal-organic framework-derived route (UBWO-route). In the BWO-route, pristine Bi2WO6 is directly coupled with g-C3N5, whereas in the UBWO-route, Bi2WO6 is derived from a bismuth-based MOF precursor (UU-200) before combination with g-C3N5 and calcination. Structural analyses confirmed that both routes led to the in situ formation of metallic Bi0 nanoparticles and intimate interfacial contact, yielding ternary heterostructures. Notably, the MOF-derived UBWO-route induced distinct morphology, enriched surface oxygen species, and defects including nitrogen vacancies and -C≡N groups, resulting in stronger interfacial electronic coupling and enhanced charge separation. Under white LED irradiation, the optimized 15UBWO/g-C3N5 catalyst achieved 98.11% degradation of tetracycline hydrochloride (TCH) within 120 min, significantly outperforming both pristine materials and 15BWO/g-C3N5. Its apparent reaction rate constant was 3.6 and 3.0 times higher than those of g-C3N5 and UBWO, respectively, and notably higher than that of 15BWO/g-C3N5, highlighting the critical role of precursor engineering. The enhanced performance is attributed to the synergistic effects of surface plasmon resonance of Bi0, efficient S-scheme charge transfer, and strengthened interfacial electronic interactions. Reactive species trapping and band structure analysis revealed that •O2- radicals play dominant roles, while •OH contributes as a secondary oxidative species. LC-MS analysis identified multiple intermediates and proposed the TCH degradation pathway. Importantly, QSAR-based toxicity prediction combined with seed germination assays demonstrated a significant reduction in ecological toxicity after treatment. This work clarifies the precursor-dependent evolution of Bi2WO6-based heterostructures and provides a viable strategy for designing MOF-derived plasmonic S-scheme photocatalysts for efficient, environmentally safe antibiotic removal.