Acetone-Mediated Glucose Isomerization over a ZrO₂-NC Composite Catalyst

The agglomeration-prone properties of metal oxide catalysts limit their catalytic efficiency in the isomerization of glucose to fructose. Herein, the hierarchical structure and abundant coordination groups of collagen fibers were used to anchor Zr⁴⁺, and a highly dispersed ZrO₂-nitrogen-doped carbon (ZrO₂-NC) composite catalyst was subsequently fabricated by calcination. For the catalytic glucose-to-fructose isomerization over ZrO₂-NC, fructose was obtained in 41.3% yield and 85.3% selectivity in a water-acetone solvent at 120 ℃ for 10 min. The electron-deficient environment of ZrO₂ surface during charge transfer from ZrO₂-to-NC layer benefited to preferentially adsorb glucose, which accelerated glucose isomerization and fructose desorption. The amphoteric catalyst triggered both proton transfer on the Bronsted base sites and the intramolecular hydride shift of glucose on the Lewis acid sites of ZrO₂-NC in the mixed solvent. The latter isomerization mechanism depended on the presence of acetone, which lowered the energy barrier and increased fructose yield.