Amino-functionalized MIL-101(Fe)-NH2 as efficient peracetic acid activator for selective contaminant degradation: Unraveling the role of electron-donating ligands in Fe(IV) generation

Peracetic acid-based advanced oxidation processes (PAA–AOPs), which generate various reactive radicals, have garnered substantial attention for degradation emerging contaminants (ECs). However, nonselective radical-based PAA–AOPs often suffer from interference by water matrix components, causing low contaminants removal efficiency. This study explores the use of amino-(NH 2 )-functionalized metal–organic frameworks (MIL-101(Fe)-NH 2 ) as heterogeneous catalysts for PAA activation, enabling the generation of high-valent iron- (Fe)–oxo species (Fe(IV)) capable of efficiently degrading ECs (80 −100 %, within 30 min). The Fe(II) clusters in MIL-101(Fe)-NH 2 , modulated by electron-donating −NH 2 groups, play a pivotal role in Fe(IV) generation. Scavenger and probe experiments confirmed Fe(IV) as the primary reactive species responsible for ECs degradation. Density functional theory calculations demonstrated that the four-electron transfer to generate Fe(IV) has lower free energy than the two-electron transfer to generate organic radicals (e.g., CH 3 COO • and CH 3 C(O)OO • ). Furthermore, thermodynamically unfavorable CH 3 COO • desorption further promotes Fe(IV) generation. The PAA/MIL-101(Fe)-NH 2 system efficiently degraded SMX ( k app = 121.2 −287.2 M −1 s −1 ) and other ECs ( k app = 40 −432 M −1 s −1 ) with minimal interference from water matrix components and excellent reusability. This study demonstrates that MIL-101(Fe)-NH 2 is a robust catalyst for PAA activation and provides a novel approach for selectively generating Fe(IV) for ECs degradation.