Ligand Field-Engineered Frontier Orbital Alignment in MXenes-Supported Single-Atom Catalysts for Enhanced Propane Dehydrogenation

Single-atom catalysts (SACs) offer a transformative strategy for propane dehydrogenation (PDH) by maximizing atom efficiency and enabling precise active-site control. Their performance, however, is intrinsically linked to the electronic properties of the support. This study reveals the essential role of the ligand field in determining the stability and activity of SACs supported on V₃C₂O₂ MXene. We demonstrate that the ligand field lifts the degeneracy of metal d-orbitals, and a strong field induces a large splitting energy, which minimizes the HOMO-LUMO gap. This electronic modulation strengthens the SAC binding and enhances catalytic activity, yielding significantly lower C-H activation barriers compared with conventional metal surfaces. The reaction pathway involving the coadsorption of a propyl fragment and a hydrogen atom at the pure metal site (P3) outperforms those on mixed metal-oxygen (P2) or pure oxygen (P1) sites. Catalyst regeneration via hydrogen desorption proceeds most readily through homolytic coupling, is moderately challenging via heterolytic recombination, and is most difficult through dihydrogen formation. Pt-SAC exhibits superior stability and the lowest energy barriers among all systems owing to its pronounced d-orbital splitting and narrow frontier orbital gap. These insights establish V₃C₂O₂-supported SACs as a versatile platform for PDH, in which crystal field-mediated frontier orbital interactions enable the fine-tuned regulation of reactivity from C-H activation to hydrogen desorption.