WS2 enhances the Fe2+/Fe3+ cycle in MIL-101(Fe) to promote the activation of peroxymonosulfate for phenol degradation

To address the low Fe 3+ /Fe 2+ redox cycling efficiency of Fe-based catalysts during peroxymonosulfate (PMS) activation, this study successfully constructed a MIL-101(Fe)/WS 2 composite catalytic material. The results show that the MW 1:1 composite exhibits excellent performance toward PMS activation. By leveraging the cooperative effect of dual-metal cycling between Fe 3+ /Fe 2+ and W 4+ /W 6+ , as well as unsaturated sulfur vacancies, it achieves 97% phenol degradation within 60 min, with a reaction constant of 0.1038 min −1 , which is approximately 110 times that of single MIL-101(Fe) and WS 2 . The effects of key operating parameters such as catalyst dosage, PMS concentration, pH value and coexisting anions on phenol degradation efficiency were systematically evaluated. Through in-depth radical quenching experiments and electron spin resonance (ESR) spectroscopy analysis, it was clearly identified that sulfate radical ( SO 4 ∙ − ${\mathrm{SO}}_4^{\bullet -}$ ) and singlet oxygen ( 1 O 2 ) were the main active oxide species driving the degradation reaction. Furthermore, this study further elucidated the degradation means of phenol, proclaimed the reaction mechanisation, and evaluated the ecological toxicity of phenol and its intermediate products using the ECOSAR model. This work provides new insights for constructing efficient iron-based catalysts to activate PMS and promoting its application in the control of refractory organic pollutants.