Modulated construction of Fe-based MOF via formic acid modulator for enhanced degradation of sulfamethoxazole：Design, degradation pathways, and mechanism

Metal-organic frameworks (MOFs) have attracted more attention because of their excellent environmental catalytic capabilities. Modulation approach as an advanced assistant strategy is vital essential to enhancing the performance of MOFs. In this study, the modulated method was used to successfully synthesize a group of Fe-based MOFs, with formic acid as the modulator on the synthesis mixture. The most modulated sample Fe-MOFs-2 exhibit high specific surface areas and higher catalytic activity, which could effectively degrade SMX via PS activation, with almost 95% removal efficiency within 120 min. The results revealed that the % RSE of modulated Fe-MOFs-2 increased from 2.31 to 3.27 when compared with the origin Fe-MOFs. This may be due to the addition of formic acid induces the formation of more coordinatively unsaturated metal sites in the catalyst, resulting in structural defects. In addition, the quenching experiment and EPR analysis verified SO4-·and·OH as the major active free radicals in the degradation process. Modulated Fe-MOFs-2 demonstrated good reusability and stability under fifth cycles. Finally, four possible degradation pathways and catalytic mechanism of Fe-MOFs-2 was tentatively proposed. Our work provides insights into the rational design of modulated Fe-MOFs as promising heterogeneous catalysts for advanced wastewater treatment.