Investigating the Role of UiO-68 Supported N-Heterocyclic Carbene-Based Metal-Hydrides for CO Hydrogenation to Methanol.

Methanol synthesis typically occurs using syngas (CO, CO2, and H2) over Cu/ZnO/Al2O3 catalyst. However, this process involves a lot of ambiguities related to the nature of active site, the relative role of CO and CO2, the importance of metal-support interaction and the true source of C in methanol. Motivated by these challenges, it is computationally studied UiO-68 supported N-heterocyclic carbene-based coinage metal hydrides (NHC-M(I)-H) as single-atom catalysts for methanol synthesis, focusing specifically on CO hydrogenation as a simplified and efficient route. The study confirms that NHC-Cu(I)-H can catalyze methanol synthesis with CO as the only C source. Hence, it can eliminate CO2 from the reaction mixture which will otherwise complicate product separation due to water formation. Moreover, methanol synthesis from CO is more hydrogen-efficient and energy saving compared to that from CO2. The calculated activation barrier of methanol synthesis from CO over UiO-68 supported NHC-Cu(I)-H catalyst is lower than those reported for methanol synthesis from CO2 over various Cu-surfaces and nobel metal-based catalysts. Overall, the study demonstrates that CO hydrogenation over UiO-68 supported NHC-Cu(I)-H is not only a viable and efficient route for methanol production but also provides an attractive alternative to traditional Cu/ZnO/Al2O3-based systems.