Rationally designed MIL-101(Fe)/WO3 S-scheme heterojunction coupled with peroxymonosulfate for boosting the visible-light-driven photodegradation of tetracycline hydrochloride

Developing S-scheme photocatalysts with excellent catalytic activity and convenient retrieval is highly desirable for wastewater purification. Herein, a novel S-scheme MIL-101(Fe)/WO3 heterojunction on carbon cloth is successfully synthesized via a facile solvothermal approach. The optimized MIL-101(Fe)/WO3 composite (MWC1.5) has been found to be highly effective in activating peroxymonosulfate (PMS) and then degrading tetracycline hydrochloride (TC-HCl) with a 100% degradation rate when exposed to visible light (Vis) within a period of 20 min. Such MWC-1.5/PMS/Light system also shows stable cycling performance and good recyclability. The remarkable photocatalytic degradation performance is mainly attributed to the powerful intrinsic electric field that accelerates the separation of photogenerated charge carriers via the S-scheme charge transfer. Radical quenching experiments and electron paramagnetic resonance (EPR) results suggest that center dot SO4 - and center dot OH are the major oxidizing substances in the photocatalytic processes. Three potential degradation pathways are deduced based on an in-depth analysis of the degradation intermediates and the degradation mechanism is also elucidated through a rational combination of the experimental studies and theoretical calculations. This novel hybrid photocatalyst system has been shown to be a promising strategy for environmental remediation, while also suggesting a feasible approach for the development of photocatalysts with both remarkable activity and stability.