Single-Atom MnN<sub>5</sub> Catalytic Sites Enable Efficient Peroxymonosulfate Activation by Forming Highly Reactive Mn(IV)–Oxo Species
Jie Miao, Jian Song, Junyu Lang, Yuan Zhu, Jie Dai, Yan Wei, Mingce Long, Zongping Shao, Baoxue Zhou, Pedro J. J. Alvarez, Lizhi Zhang
Abstract
Four-nitrogen-coordinated transitional metal (MN 4 ) configurations in single-atom catalysts (SACs) are broadly recognized as the most efficient active sites in peroxymonosulfate (PMS)-based advanced oxidation processes. However, SACs with a coordination number higher than four are rarely explored, which represents a fundamental missed opportunity for coordination chemistry to boost PMS activation and degradation of recalcitrant organic pollutants. We experimentally and theoretically demonstrate here that five-nitrogen-coordinated Mn (MnN 5 ) sites more effectively activate PMS than MnN 4 sites, by facilitating the cleavage of the O–O bond into high-valent Mn(IV)–oxo species with nearly 100% selectivity. The high activity of MnN 5 was discerned to be due to the formation of higher-spin-state N 5 Mn(IV)═O species, which enable efficient two-electron transfer from organics to Mn sites through a lower-energy-barrier pathway. Overall, this work demonstrates the importance of high coordination numbers in SACs for efficient PMS activation and informs the design of next-generation environmental catalysts.