MOF-Encapsulating Metal–Acid Interfaces for Efficient Catalytic Hydrogenolysis of Biomass-Derived Aromatic Aldehydes

Developing an efficient and selective catalyst for C–O hydrogenolysis of biomass-derived aromatic aldehydes, such as 5-methylfurfural (MF), 5-hydroxymethylfurfural (HMF), and vanillin (VA), is highly significant for the synthesis of biofuel and fine chemicals. Herein, metal–organic framework (MOF)-encapsulating metal–acid interfaces (Pd@UiO–CH2SO3H, Pd@UiO–PhSO3H) were first reported. Compared with traditionally supported catalysts (Pd/UiO–SO3H, Pd/UiO–NH2), Pd–acid-interface-encapsulated MOFs show much higher activity and selectivity for MF to 2,5-dimethylfuran (DMF), HMF to DMF, and VA to 2-methoxy-4-methylphenol (MMP) reactions. In particular, Pd@UiO–SO3H shows the best catalytic performance with 89.0 and 86.0% DMF yield from MF and HMF and a 99.4% MMP yield from VA based on its suitable hydrophilicity, high hydrogen activation ability, and abundant Pd–SO3H interface active sites. According to the catalytic performance of Pd/UiO–NH2 and the results of an ATR-IR test, the acidic sites on the Pd–acid interface can accelerate the activation of the hydroxyl group for these hydrogenolysis reactions. This work provides an effective design strategy for the preparation of MOF-encapsulating metal–acid interfaces and shows the powerful synergistic effect of hydrogenation and acid catalysis.