Engineering MOF-Derived Bi₂WO₆ via In Situ Bi⁰ Formation for Plasmonic S-Scheme Bi₂WO₆/Bi/g-C₃N₅ Heterostructure for...

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.