Axially engineered single atoms in enzyme-mimic-binding pocket steering dehalogenation-polymerization pathways toward water pollutant upcycling.

Abstract

Polymerization-based advanced oxidation processes (P-AOPs) represent a promising strategy for simultaneous pollutant abatement and water resource recovery. However, selective removal of halogenated organic pollutants via P-AOP remains challenging due to uncontrollable oligomerization pathways and radical chain inhibition induced by the chlorine substituent. Here, we develop an axial-nitrogen-coordinated single-atom iron catalyst (Fe-NCN) that triggers an electron-transfer pathway (ETP) via enhanced electronic pulling on 2,4,6-trichlorophenol (TCP), achieving near-complete dechlorination and catalytic transformation into polymeric products. Spectroscopic characterization and theoretical calculations reveal that the axial coordination of Fe-NCN regulates peroxymonosulfate (PMS) activation to form surface PMS* complex, which oxidizes the adjacent TCP via a short-range ETP regime due to the charge-constrained nature of the carbon nitride substrate. Upon electron extraction from TCP, PMS* is transformed into an active surface hydroxyl intermediate (OH^-*), which attains nucleophilic substitution of organochlorine, subsequently triggering C-O crosslinking of the hydroxylated by-products with ultra-high electron utilization efficiency (~353%). This integrated dechlorination-hydroxylation-polymerization process can be scaled up for device-scale wastewater treatment with excellent stability. The collected oligomers can be processed to manufacture industrial-grade plastic products. This study advances the understanding of the complex polymerization regime of chlorinated micropollutants by using engineered atomic catalysts for sustainable and low-emission water purification.