Highly efficient Fe-based single-atom catalysts derived from S-doped metal-organic framework (MOF) for heterogeneous Fenton-like reactions

Single-atom catalysts (SACs) have attracted considerable interest in heterogeneous Fenton-like reactions (HTFR). However, their efficiency and practical applicability require further improvement. To address this, an S-doping strategy was employed, using zeolitic imidazolate framework-8 (ZIF-8) as a precursor to fabricate Fe-based SACs (Fe-SNC) for peroxymonosulfate (PMS) activation. X-ray absorption fine structure (XAFS) analysis confirmed the coordination of atomically dispersed Fe to N and S atoms, forming a Fe–N 2 S 2 configuration. In a separate adsorption test, Fe-SNC achieved 93.1% removal of tetracycline (TC). Furthermore, TC could be removed within 40   min during PMS-based HTFR catalyzed by Fe-SNC, exhibiting significantly high performance compared to the pristine Fe-NC catalyst. Additionally, the activation energy for PMS activation was decreased to 2.87   kJ/mol with Fe-SNC, which is only 26.16% of that required for Fe-NC (10.97   kJ/mol). The superior performance of Fe-SNC is attributed to its enhanced adsorption capacity and high PMS activation ability. Density functional theory (DFT) calculations further revealed that S-doping significantly enhanced the adsorption energy between catalyst and PMS to -2.95   eV. It also promoted the elongation of O–O (1.477   Å) and S–O (1.873   Å) bonds, while facilitating charge transfer of 0.79 e. The galvanic oxidation process (GOP) also demonstrated that the electron transfer process played a key role during the PMS-based HTFR catalyzed by Fe-SNC. The quenching experiments and EPR tests further confirmed that the 1 O 2 and Fe(IV)=O were the primary reactive species. This work provides insightful perspectives for the rational design of highly efficient SACs for HTFR.