Efficient cascade conversion of glucose to levulinic acid using a dual-functional UiO-66 catalyst†

Abstract

The catalytic properties of UiO-66 were enhanced through a post-synthetic defect engineering method. This involved facile treatment of the material with aqueous HCl to induce defects that generated free carboxylic acid (–COOH) groups. Consequently, the modified UiO-66 framework incorporated both Brønsted acidic –COOH groups and Lewis acidic sites, which originate from inherent linker-missing defects. These dual-functional acidic sites, combined with the high structural stability of UiO-66, enable it to act as an efficient heterogeneous catalyst for one-pot, multistep reactions. Specifically, the catalyst facilitates the conversion of glucose to levulinic acid (LEV) in the presence of sodium chloride (NaCl) as a promoter under hydrothermal conditions. Under optimized conditions (190 °C for 6 h), the catalytic system achieves a remarkable conversion of glucose (>99%), with an impressive 83% yield of LEV. The defect-engineered UiO-66 catalyst shows exceptional potential as a candidate for sugar conversion to valuable bio-based chemicals.