Porous Hafnium Phosphonate: Novel Heterogeneous Catalyst for Conversion of Levulinic Acid and Esters into γ‑Valerolactone

Catalytic transfer hydrogenation (CTH) of levulinic acid (LA) and its esters to produce γ-valerolactone (GVL) is an important route for biomass transformation. Development of efficient and heterogeneous catalysts for the GVL production via CTH reaction of LA and its esters has attracted much attention. In this work, a new hafnium (Hf) containing organic–inorganic hybrid catalyst (Hf-ATMP) was prepared by the reaction of HfCl4 and amino tri­(methylene phosphonic acid) and was used to catalyze the CTH reaction of LA and its esters to produce GVL using isopropanol as the hydrogen source. It was found that the prepared Hf-ATMP could catalyze the CTH reaction to provide satisfactory GVL yield, and the effects of reaction temperature, reaction time, and the amount of the catalyst on the reaction were studied in detail. Meanwhile, the Hf-ATMP could be reused at least five times without notable decrease in activity and selectivity. Systematic studies indicated that the acidity of Hf, the basicity of the phosphate groups, and the porosity of the prepared catalyst were the main reasons for the catalytic performance of Hf-ATMP in the CTH reaction of LA and its esters.