Beyond passive degradation: Pre-adsorbed pollutants as electronic modulators for enhanced PMS activation on single-atom iron sites

A novel “pollutant-triggered catalysis” paradigm is proposed, using pre-adsorbed pollutants as electronic modulators to optimize peroxymonosulfate (PMS) activation over mono-disperse iron single atoms anchored on porous carbon nitride (Fe SAC /CN) for water remediation, unlike conventional strategies treating contaminants as passive targets. Catalytic tests, spectroscopic analyses, and density functional theory calculations were integrated to clarify the effect of pre-adsorbed electron-rich 4-chlorophenol on the electronic configuration of Fe sites and the PMS activation mechanism. The pre-adsorbed pollutant enhanced Fe-site Bader charge transfer and upshifted the Fe 3d-band center, thereby strengthening PMS adsorption, lowering the activation barrier, shifting the dominant pathway toward Fe(IV)=O and 1 O 2 rather than radicals, enabling 100% 4-chlorophenol removal within 15 min, and yielding a 5.34-fold rate enhancement over pristine Fe SAC /CN. The results reveal that substrate-induced electronic modulation of single-atom Fe sites is a viable route to regulate reactive species generation and improve catalytic performance. By redefining contaminants as active electronic modulators, this work offers a scalable paradigm for sustainable water remediation that simultaneously enhances oxidation capacity and environmental applicability.