Electronic effect-guided ligand functionalization of MIL-101 (Fe): Unlocking a new perspective for regulating ROS generation in Fenton-like systems

In peroxymonosulfate (PMS)-based advanced oxidation processes (AOPs), the precise regulation of reactive oxygen species (ROS) generation pathways is a core challenge for achieving selective degradation of target pollutants. In this study, we propose an electronic effect-guided ligand functionalization strategy by systematically introducing electron-donating (-OH, -NH 2 ) and electron-withdrawing (-NO 2 ) groups into the MIL-101 (Fe) framework, thereby establishing a quantitative structure-activity relationship between the electronic structure, coordination environment of Fe centers and ROS generation. The results demonstrate that electron-donating groups (-OH, -NH 2 ) significantly promote the non-radical pathway dominated by singlet oxygen ( 1 O 2 ), achieving efficient degradation of the electron-rich pollutant sulfamethoxazole (SMX) with removal efficiencies of 93.0% and 91.2%, respectively. Notably, the 1 O 2 contribution rate in the MIL-101(Fe)-OH system reached 95.07%. Correlation analysis reveals a significant positive correlation between C O content and 1 O 2 contribution. Combined experimental characterization and DFT calculations indicate that the selective generation of ROS results from the synergistic effects of multiple factors, including electronic structure, adsorption energy, and charge transfer. Electron-donating groups enhance the electron density at the Fe center, elongate the Fe O bond length, and optimize PMS adsorption energy, thereby promoting the self-disproportionation of the key SO 5 •- intermediate to generate 1 O 2 . This work highlights the promotional role of functional group electronic effects on the non-radical pathway, elucidates the core mechanism governing ROS generation, and provides a mechanistic framework for the design of highly selective Fenton-like catalysts. Environmental implication This study employs an electron-effect-guided ligand functionalization strategy to systematically reveal the structure–activity relationship between the electronic structure and coordination environment of metal nodes in Fe-MOFs and the ROS generation. The electronic effects of functional groups enable the precise regulation of ROS, and electron-donating groups significantly promote nonradical pathways, thereby achieving efficient degradation of the electron-rich contaminant sulfamethoxazole. This work highlights the promotion of nonradical pathways by the electronic effects of functional groups, clarifies the core mechanism governing ROS generation, and provides new insights for the design of highly efficient and selective catalysts.