Regulating Reactive Oxygen Intermediates of SAzyme via Second-Shell coordination for Selective Aerobic Oxidation

Reactive oxygen species (ROS) regulation for artificial oxidoreductase is a key scientific issue that determines the activity, selectivity, and stability of aerobic reaction. However, the poor understanding of ROS formation mechanism greatly hampers their wider deployment. Herein, inspired by cytochromes P450 affording bound ROS intermediates in O2 activation, we report single-atom FeN4 site with tunable second-shell anion could regulate ROS generating pathways. Remarkably, the second-shell S anion coordinated FeN4 (denoted as FeNSC) delivers 2.4-fold higher oxidase-like activity and only 17% free ROS generation compared to FeNC. The detailed XANES analysis and DFT calculations reveal that the second shell S-doping significantly altered the electronic structure of FeN4 sites, leading to an increase of electron density at Fermi level and the enhanced electron transfer from active sites to the key intermediate *OOH, thereby determining the type of ROS in aerobic oxidation process. FeNC with different second-shell anion were further applied to drive aerobic oxidation reaction with enhanced activity, selectivity, and stability.