Catalytic Transfer Hydrogenation of Biomass‐Derived Carbonyls over Hafnium‐Based Metal–Organic Frameworks

A series of highly crystalline, porous, hafnium‐based metal–organic frameworks (Hf‐MOFs) have been shown to catalyze the transfer hydrogenation reaction of levulinic ester to produce γ‐valerolactone by using isopropanol as a hydrogen donor. The results are compared with their zirconium‐based counterparts. The role of the metal center in Hf‐MOFs has been identified and reaction parameters optimized. NMR studies using isotopically labeled isopropanol provide evidence that the transfer hydrogenation occurs through a direct intermolecular hydrogen transfer route. The catalyst, Hf‐MOF‐808, can be recycled several times with only a minor decrease in catalytic activity. The generality of the procedure has been demonstrated by accomplishing the transformation with aldehydes, ketones, and α,β‐unsaturated carbonyl compounds. The combination of Hf‐MOF‐808 with the Brønsted‐acidic Al‐Beta zeolite gives the four‐step one‐pot transformation of furfural to γ‐valerolactone in good yield of 75 %.