Optimal Oxophilicity at the Fe‐N x Interface Enhances the Generation of Singlet Oxygen for Efficient Fenton‐Like Catalysis

Abstract In the pursuit of efficient singlet oxygen generation in Fenton‐like catalysis, the utilization of single‐atom catalysts (SACs) emerges as a highly desired strategy. Here, a discovery is reported that the single‐atom Fe coordinated with five N‐atoms on N‐doped porous carbon, denoted as Fe‐N 5 /NC, outperform its counterparts, those coordinated with four (Fe‐N 4 /NC) or six N‐atoms (Fe‐N 6 /NC), as well as state‐of‐the‐art SACs comprising other transition metals. Thus, Fe‐N 5 /NC exhibits exceptional efficacy in activating peroxymonosulfate for the degradation of organic pollutants. The coordination number of N‐atoms can be readily adjusted by pyrolysis of pre‐assembly structures consisting of Fe 3+ and various isomers of phenylenediamine. Fe‐N 5 /NC displayed outstanding tolerance to environmental disturbances and minimal iron leaching when incorporated into a membrane reactor. A mechanistic study reveals that the axial ligand N reduces the contribution of Fe‐3d orbitals in LUMO and increases the LUMO energy of Fe‐N 5 /NC. This, in turn, reduces the oxophilicity of the Fe center, promoting the reactivity of *OO intermediate—a pivotal step for yielding singlet oxygen and the rate‐determining step. These findings unveil the significance of manipulating the oxophilicity of metal atoms in single‐atom catalysis and highlight the potential to augment Fenton‐like catalysis performance using Fe‐SACs.