High-Curvature Interfaces Induce Nondegenerate Splitting of <i>d</i>-Orbital Energy Levels for Enhanced Catalytic Activity

The construction of hierarchical pores, especially mesopores, usually leads to abundant interfaces with high curvature, while the recognition of the impact of interface curvature upon intrinsic reactivity is yet limited. In this work, a large number of high-curvature interfaces were identified in the as-synthesized mesoporous catalysts (Cu/Ni-MNC-T_<i>x</i>, MNC = mesoporous nitrogen-doped carbon) through advanced three-dimensional reconstruction technologies. It was further confirmed that high-curvature interfaces can induce nondegenerate splitting of <i>d</i>-orbital energy levels in the affixing metal sites. As a result, Cu/Ni-MNC-T₆₀ exhibited a significantly reduced apparent activation energy (from 102.7 to 52.8 kJ·mol^-1) and remarkably promoted intrinsic activity (reduced energy barriers by 60%) in the hydrogenation of furfural. DFT calculations revealed that the abundant high-curvature interfaces of Cu/Ni-MNC-T₆₀ accomplished a parallel adsorption of furfural on Cu sites and also facilitated H₂ splitting on Ni sites. Furthermore, in the rate-determining step, the C-OH bond of the key *fur-CH₂OH intermediate not only exhibited an impaired electron enrichment at the nearby oxygen end but also displayed an elongated bond length, indicating effective C-OH bond activation with the reduced hydrogenation energy barrier. The application feasibility of such a promotion mechanism was additionally verified by the considerable hydrogenation performances of Cu/Ni-MNC-T₆₀ for a wide scope of aldehydes.