Unraveling H2 dissociation in CO2 hydrogenation on frustrated Lewis pair-functionalized UiO–67: DFT and nuclear quantum effects

Abstract

Understanding hydrogen (H2) activation is fundamental to developing efficient CO2 hydrogenation catalysts. Thus, in this study, we examine H2 dissociation and subsequent CO2 hydrogenation on 12 UiO–67 frameworks functionalized with frustrated Lewis pairs (FLPs), employing both conventional density functional theory (DFT) and multicomponent DFT (MC_DFT) to account for nuclear quantum effects (NQEs). The results reveal that all FLP–MOFs lower the H2 activation barrier through heterolytic cleavage, with NQEs further reducing the barriers—most notably in systems containing electron-donating groups (EDGs), where pronounced H–H bond elongation characterizes the transition state. Conversely, FLPs bearing strong electron-withdrawing groups stabilize the 2H adsorption state, rendering H2 dissociation thermodynamically favorable but suppressing CO2 hydrogenation owing to excessively strong hydrogen binding. Strong correlations are observed among H2 dissociation energies, CO2 hydrogenation activation barriers, and FLP acidity, enabling catalytic performance prediction. Incorporating NQEs enhances these correlations, providing a refined descriptor for rational catalyst screening. Overall, this study highlights the critical role of NQEs in hydrogen activation and demonstrates that EDG-functionalized FLP–MOFs are particularly promising candidates for promoting H2 activation and CO2 conversion.