Precise synthesis of Fe single-atom catalysts on montmorillonite/g-C3N4 heterostructures for highly efficient fenton-like degradation of organic pollutants.

Single-atom Fenton-like catalysts supported on graphitic carbon nitride (g-C3N4) show great potential for aqueous organic pollutant degradation but are hindered by structural heterogeneity and inefficient metal anchoring. Herein, a precise synthesis strategy that can balance metal precursor supply and anchoring site formation is proposed to construct iron single-atom catalysts (Fe-SACs) on a g-C3N4/montmorillonite (MMT) heterostructure. Directional electron transfer from MMT to g-C3N4 was found to strengthen metal-support interactions, optimizing interfacial electron redistribution and significantly enhancing both catalytic activity and stability. The optimized FNC-MMT (Fe@C3N4-MMT) SACs system achieved >95 % pollutant degradation efficiency over 2000 min in continuous flow operation, with a kinetic rate constant (k = 1.4404 min-1) 36-, 758-, and 2880-fold higher than Fe- C3N4 SACs, pristine g- C3N4, and individual MMT, respectively. Under visible light, the heterostructure exhibited exceptional photocatalytic cycling performance, confirming the critical role of interfacial electron synergy. Mechanistic studies revealed that the system activates peroxymonosulfate (PMS) via a non-radical pathway dominated by 1O2 generation and direct electron transfer, as evidenced by in situ Electron spin resonance (ESR) and electrochemical analysis like Galvanic oxidation process. DFT calculations further demonstrated that MMT optimizes the electronic structure of Fe sites, lowering the energy barrier for PMS activation. This work provides a scalable approach for synthesizing stable SACs as well as fundamental insights into electronic-structure-mediated non-radical catalysis, advancing the design of high-efficiency systems for water purification.