Photocatalytic degradation of tetracycline by UiO-66-S-FeS composites for visible light: Mechanistic on compact interfacial and degradation pathways

Abstract

Photocatalysis encounters a major challenge in developing catalysts that are capable of functioning stably and efficiently absorbing visible light. In this study, we designed and synthesized the UiO-66-S-FeS photocatalyst, which featured a type I heterojunction. Its successful synthesis was validated by characterization analyses. The UiO-66-S-FeS catalyst exhibited a “shell-core” structure, with FeS firmly anchored to the surface of UiO-66-SH₂ via Fe-S bonds, creating a robust interface. The interface significantly enhanced the rate of photogenerated carrier transfer and separation during photocatalytic reactions. While retaining the original advantages of active site dispersion and high specific surface area of MOFs, the doping of FeS resulted in good visible light absorption performance. Ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS) revealed that the visible light absorption scope of UiO-66-S-FeS_0.5 was effectively broadened compared to UiO-66-SH₂. It resulted in a remarkable improvement in tetracycline degradation, achieving a degradation rate of 99.5 % under visible light. Electron spin resonance (ESR) and free radical scavenging experiments identified several reactive species, including ·O₂⁻, h⁺, ·OH and ¹O₂ playing roles in the degradation process. These findings supported the degradation mechanism as a type I heterojunction. This study demonstrated the potential of the UiO-66-S-FeS photocatalyst for effectively removing antibiotic contaminants.