Interlayer Magnetic Ordering in Two-Dimensional Metal–Organic Frameworks for Electrocatalytic Oxygen Reduction: A Grand Canonical Density Functional Theory Study

Herein, we present a theoretical framework to uncover the crucial roles of interlayer magnetic exchange of two-dimensional hexaaminobenzene (HAB)-based metal-organic frameworks (TM-HAB) catalysts on electrocatalytic oxygen reduction reaction (ORR) performance. Through multistage screening, monolayer Fe-HAB-I and Co-HAB-I were identified as optimal for 4e^- and 2e^- ORR pathways, respectively. Grand Canonical Density Functional Theory (GC-DFT) and Monte Carlo simulations revealed monolayer Co-HAB-I prefers to a 2e^- ORR with an onset potential of 0.95 V vs RHE under alkaline conditions, while Fe-HAB-I exhibits 4e^- ORR activity at the onset potential of 0.73 V vs RHE in acidic environments. For experimentally relevant multilayer systems, GC-DFT calculation of bilayer Fe-HAB-II highlights the critical role of interlayer magnetic coupling: the ferromagnetic (FM^II) state demonstrates a markedly higher onset potential than the antiferromagnetic (AFM^II) state at pH = 13. Notably, Fe-HAB-II in the FM^II state achieves a theoretical onset potential of 1.17 V vs RHE, closely aligning with experimental observations (1.02 V vs RHE), thereby validating the crucial roles of interlayer spin exchange on ORR property. This work underscores the pivotal influence of interlayer magnetic interactions in optimizing two-dimensional electrocatalysts for ORR.