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.