Engineering Lewis Acid Sites via Oxygen Vacancies in V ₂ CO ₂ MXene for Electrophilic C–H Activation in Propane Dehydrogenation

While defect engineering is a recognized strategy for enhancing the properties of two-dimensional materials, its targeted application to MXenes for propane dehydrogenation (PDH) remains largely unexplored. This work demonstrates that precisely engineered oxygen vacancies unlock superior PDH performance in V 2 CO 2 MXene. Density functional theory (DFT) calculations reveal that a single oxygen vacancy (O v ) generates coordinatively unsaturated vanadium sites, upshifting their d-band center toward the Fermi level. This defect fundamentally alters the C–H activation mechanism from the nucleophilic attack by oxygen (Lewis base) on pristine surfaces to an electrophilic attack by exposed vanadium (Lewis acid). Consequently, hydrogen abstraction targets the bonding (σ) orbital instead of the antibonding (σ*) orbital, forming a more stable V–H – Lewis pair compared to O–H + pair on the pristine surface. This reconfigured active site reduces the activation barrier for the initial C–H cleavage and promotes a strong Lewis acid–base interaction between coadsorbed hydrogen atoms, ultimately facilitating more efficient hydrogen desorption. These findings establish oxygen vacancy engineering as a viable strategy for creating high-performance MXene-based PDH catalysts.