Effect of axial coordination on oxygen reduction/evolution reaction of 2D Mn3(HXBHYB)@MOF

Developing efficient and stable oxygen reduction/evolution reaction (ORR/OER) catalysts is crucial to enhance energy conversion efficiency and reduce reliance on precious metals. This study focuses on the rational design of single-atom catalysts (SACs) and the modulation of their ORR/OER catalytic performance via coordination environment engineering. Through density functional theory (DFT) calculations, we systematically investigated the effects of axial coordination on the electrocatalytic ORR/OER performance of TMN₄-group-supported catalysts. Specifically, axial-coordinated 2D Mn 3 (HXBHYB)-Ls@MOF systems (where Ls denotes axial ligands: -OH/-Cl) were constructed to probe the tuning effects of axial ligands on the ORR/OER activity of -MnA₂B₂ moieties. Key findings reveal that: (i) The p z orbitals of axial ligands interact with the d z ₂ orbitals of Mn, modulating the magnetic moment and d -orbital distribution of Mn centers; (ii) This electronic regulation optimizes the adsorption strength of O* and OH* intermediates on Mn sites, thereby synergistically enhancing ORR/OER performance; (iii) The -OH ligand demonstrates superior ORR modulation compared to -Cl. Notably, promising catalyst configurations were identified, including OH-MnN₄ ( η ORR = 0.307 V) and Cl-MnN₂O₂ ( η OER = 0.358 V). This work elucidates the pivotal role of axial ligands in regulating electronic energy levels and spin states, paving the way for designing high-performance bifunctional electrocatalysts. • Discovered that axial -OH/-Cl ligands modulate the electronic configuration of Mn active centers through p z - d z ² orbital hybridization, inducing high-spin state formation. • Identified five exceptional-performance configurations (e.g., Cl-MnN 2 O 2 ) achieving synergistic OER/ORR bifunctional enhancement. • Revealed superior ORR modulation efficacy of -OH ligands versus -Cl counterparts while maintaining comparable OER regulatory effects.