Selective Conversion of Glucose to Levulinic Acid Catalyzed by HPAs/MOF-5 in a Hydrophilic Eutectic Solvent System

The development of efficient catalytic systems is critical for increasing the production of high-value chemicals from low-cost glucose. Here, MOF-5 was evaluated as a promising support for the synthesis of a heterogeneous catalyst with both Brønsted acid and Lewis acid sites via simple phosphotungstic heteropoly acid (HPA) embedding. In green deep eutectic solvent (DES) media, the MOF-5-supported HPA catalyst demonstrated high catalytic activity for the production of levulinic acid (LA) from glucose. The highest LA yield of 56.7 mol % was achieved at 130 °C for 3 h. The reaction efficiency of the entire reaction chain (glucose → fructose → 5-hydroxymethylfurfural → LA) was increased by adjusting the ratio of Brønsted acid sites to Lewis acid sites. Synergies between Brønsted acid, Lewis acid, and DESs are also considered to influence the reaction.