Engineering Low‐Coordination Fe–N 3 in Single‐Atom Nanozyme Breaks Activity Limitation for Water Remediation and Monitoring

ABSTRACT Developing efficient and green water treatment strategies for phenolic and estrogenic pollutants is crucial in industrial and domestic wastewater. This study innovatively proposes a low‐coordination engineering strategy to construct single–atom nanozymes with defined Fe─N 3 sites (Fe─N 3 SAzyme) for catalytic degradation and detection. The Fe─N 3 SAzyme exhibits excellent peroxidase‐like (POD‐like) and oxidase‐like (OXD‐like) activities, with an activity 11.3‐fold higher than that of the precursor Fe─doped zinc–azolide framework (Fe─ZAF). It demonstrates strong tolerance to harsh pH/temperature conditions and exceptional stability, maintaining ∼100% activity after 160 days and >93% after eight reuse cycles. Experimental and theoretical results reveal that the unique low‐coordination structure of Fe─N 3 effectively optimizes the electronic state of the active center compared with Fe─ZAF, significantly enhancing the affinity for H 2 O 2 and the efficiency of generating highly reactive oxygen radicals. Owing to its superior catalytic performance, the Fe─N 3 SAzyme achieves an efficient degradation (> 95%) of various pollutants, including phenols and estrogens. Furthermore, Fe─N 3 SAzyme is successfully integrated into a catalytic‐colorimetric detection platform for the sensitive detection of three types of estrogens. This work provides an efficient, broad‐spectrum catalyst for environmental remediation and guides the design of high‐performance single‐atom materials.