Construction of OVs-mediated TiOF2/MIL-125 (Ti) S-scheme heterojunctions for efficient antibiotics destruction: Mechanism, degradation pathway, and toxicity analysis

The advancement of photocatalysts for high-efficiency degradation of antibiotic contaminants is essential in addressing environmental issues. Herein, an S-scheme TiOF2/MIL-125 (Ti) heterojunction is synthesized for tetracycline hydrochloride (TCH) degradation. The kinetic constant for FT 1-10 (0.01710 min- 1) was 10.69 and 2.83 folds larger than TiOF2 (0.00160 min- 1) and MIL-125 (Ti) (0.00604 min- 1), correspondingly. In FT 1-10, the mutable state of Ti4+/Ti3+ facilitated charge balance compensation, thereby expediting carrier separation and promoting the generation of oxygen vacancies (OVs). OVs facilitated the reduction of bandgap and broadened the range of photoresponse, thereby enhancing photocatalytic capability. Notably, work function and XPS collectively validated that, on the heterojunction interface, e- transferred to TiOF2 from MIL-125 (Ti) side. In FT 1-10, the reactive species were center dot O2-, center dot OH and h+. Furthermore, potential attack sites in TCH degradation were forecasted utilizing condensed FuKui function, and the likely pathways of TCH degradation were identified based on LC-MS. Comprehensive toxicity and mutagenicity analyses performed on TCH degradation intermediates have demonstrated environmentally friendly nature of FT 1-10. Generally, S-scheme heterojunctions were favorable for carriers' separation and transport due their unique charge transport pathways and strong redox effects. This study provides valuable insights into design S-scheme heterojunctions with efficient photocatalytic properties.