A complementary descriptor for elucidating selective PMS activation by iron single-atom catalysts with tunable interatomic distances.

The activation of peroxymonosulfate (PMS) for selective oxidant generation in advanced oxidation process is a sought objective when using single-atom catalysts (SACs) over conventional nanomaterials. However, challenges in controlling atomic-level morphology and understanding the intricate interplay between electronic and geometric properties that affect catalytic selectivity hinder rational material design. To address this issue, we developed a library of iron single-atom catalysts (FeSACs) featuring tunable interatomic distances ranging from 2.6 to 10.5 angstroms, facilitating the independent investigation of electronic and geometric effects. We propose a complementary descriptor (CD) integrating electronic effect index (IEE) and geometric effect index (IGE) in a weighted predictive framework. The CD strongly correlates with singlet oxygen (1O2) production in selective PMS activation by the FeSAC series. Specifically, the optimized FeSAC5.0 delivers 94.2% 1O2 selectivity and nearly complete degradation of electron-rich micropollutants. This CD framework offers a universal strategy for the rational design of high-performance SACs grounded in electronic and geometric criteria.