Mechanism of transfer hydrogenation of carbonyl compounds by zirconium and hafnium-containing metal-organic frameworks

Liquid phase catalytic hydrogenation is essential to produce platform chemicals from biomass-derived carbonyl compounds. Carbonyl compounds can be upgraded to corresponding alcohols by catalytic transfer hydrogenation using hydrogen-donor solvents and mild reaction conditions. The challenge in transfer hydrogenation is the development of selective, active, and reusable catalysts. Here we show the chemical pathway of transfer hydrogenation of benzaldehyde by Hf- and Zr-containing MOF-808 and UiO-66 catalysts. MOF-808(Hf) was the most selective catalyst with 95% selectivity to benzyl alcohol at 99% conversion. Furthermore, the quantum calculations revealed that the transfer hydrogenation by MOF-808(Hf) proceeded by Meerwein-Ponndorf-Verley (MPV) reduction, which resulted in high selectivity and conversion. These findings of the effects of metal and acid sites of these MOFs enable maximizing the selectivity for transfer hydrogenation. Moreover, understanding these effects provide opportunities for these MOFs in other biomass conversion reactions.

Automated summary

Liquid phase catalytic hydrogenation is crucial for the production of platform chemicals from biomass-derived carbonyl compounds. In this study, the chemical pathway of transfer hydrogenation of benzaldehyde by Hf- and Zr-containing MOF-808 and UiO-66 catalysts was explored. It was found that MOF-808(Hf) exhibited the highest selectivity with a conversion rate of 99%.