Axial Nitrogen Coordination Engineering of Fe Single-Atom Catalyst for Enhanced Peroxidase-like Activity.

Mimicking the hierarchical structure as well as the asymmetric Fe-N sites in natural horseradish peroxidase (HRP) is of great importance in developing Fe/CN with high peroxidase-like (POD-like) activity. In this work, Fe/CN with an asymmetric FeN moiety and ordered porous structure (FeN/CN) is fabricated by an ammonia-assisted redispersion strategy, which shows high structural similarity with HRP. Therefore, FeN/CN shows an excellent catalytic efficiency (specific activity = 117.9 U/mg, = 2185 mM s) and selectivity ( = 0.059 mM) in a POD-like reaction. Based on the high catalytic properties of FeN/CN, a sensor for the detection of carbosulfan with a low limit of detection of 3.1 nM is assembled. Interestingly, FeN/CN activates HO via a superoxide pathway, while ·OH, O, and ·O can all be detected in the FeN/CN involved catalytic system. Mechanistic study by density functional theory calculations combined with experimental results illustrates that Fe-N sites provide moderate adsorption of *OH, enlarging and decreasing the reaction energy to form ·OH and ·O, respectively, while Fe-N sites exhibited higher affinity toward the OH* intermediate, resulting in the facile O-O bond cleavage from HO molecule and prohibited the process of *OH desorption to ·OH.