Coordination‐Regulated Single‐Atom Evolution from Iron‐Conditioned Waste Activated Sludge for Low‐Carbon Fenton‐Like Water Purification

ABSTRACT Single‐atom catalysts (SACs) design remains constrained by the inability to integrate atomic‐level coordination control with mass transport and scalable synthesis. Herein, we address this challenge by developing a self‐templated heterogeneous matrix that couples coordination regulation with hierarchical accessibility within a scalable platform. Using iron‐conditioned waste‐activated sludge (WAS) as a precursor, porously nanoconfined Fe‐based SACs is constructed. The system exhibits a volcano‐type dependence of catalytic activity on iron‐conditioning dosage, with peak performance at the single‐atom loading threshold (∼0.8 wt.% Fe, corresponding to 1 mg Fe per g dry WAS). Correlative XAS/EXAFS and DFT analysis pinpoint Fe‐N 3 O 1 as the prevailing coordination environment that modulates spin states and downshifts the d‐band center, thereby facilitating deprotonation‐assisted * O– * O scission and 1 O 2 ‐formation (∼95% selectivity). Broad‐spectrum abatement of electron‐rich pollutants was achieved that persists under complex matrices in column‐scale‐up application (remain 90% over 120 h reaction). System‐level LCA and TEA confirm markedly lower cradle‐to‐gate environmental impacts and a 40‐fold reduction in operating costs relative to ZIF‐derived Fe‐SACs baselines. This work establishes a generalizable framework for SAC design and defines an “in‐plant circular catalysis” paradigm for transforming iron‐conditioned waste‐activated sludge into high‐value catalysts, charting a sustainable route toward efficient and environmentally benign Fenton‐like wastewater purification.