Structure-Sensitivity Switch on Mo₂CT_x MXene: Steering CO₂ Hydrogenation via Surface Termination and Copper...

The pursuit of precise product control in CO₂ hydrogenation represents a central challenge in catalysis, where the inherent complexity of reaction networks often obscures the fundamental connection between surface structure and catalytic selectivity. Here, by integrating density functional theory and microkinetic modeling, we systematically decouple the distinct roles of surface oxygen termination and Cu coordination geometry in regulating catalytic selectivity of Mo₂CO_x catalysts. We identify three structurally sensitive regimes: pristine Mo₂CO_x surfaces facilitate efficient C═O bond cleavage to form CO and CH₄, with higher oxygen coverage enhancing CO selectivity and promoting CH₃OH among hydrogenated products; Cu-adsorbed Mo₂CO_x enhances CH₄ generation by maintaining C═O scission while suppressing CO desorption; and Cu-doped Mo₂CO_x promotes CH₃OH formation by reducing surface oxophilicity and stabilizing key oxygenated intermediates. Crucially, we establish the Cu oxidation state as a quantitative descriptor for CH₃OH/CH₄ selectivity, with a higher valence favoring CH₃OH production. These mechanistic insights, corroborated by in situ spectroscopy and catalytic tests, bridge structure sensitivity with macroscopic performance. This work establishes general design principles for selective CO₂ conversion on MXene-based catalysts, providing a foundation for the rational design of advanced CO₂ hydrogenation systems.