Modulated zirconium metal–organic framework UiO-66 is shown to catalyze the isomerization of d-glucose to d-fructose in alcohol media. Fructose selectivity can change depending on solvent choice. We hypothesize that the difference in selectivity is related to a combined effect of adsorption and solvation effects, which may lead to the high formation of alkylglucosides in depletion of fructose if methanol or ethanol are used. A fructose selectivity of 72 % at 82 % glucose conversion in 1-PrOH was achieved. The reaction mechanism was investigated using nuclear magnetic resonance spectroscopy. We demonstrate that UiO-66 isomerizes glucose to fructose through an intramolecular C2–C1 hydride transfer. In addition, we show that modulated UiO-66 is a highly active and stable catalyst at the reaction conditions, showing great potential for other sugar reactions.
Bibliographical noteFunding Information:
This work was supported as part of the Catalysis Center for Energy Innovation, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award DE-SC0001004. M.D.dM.’s doctoral fellowship was partially supported by the Brazilian National Council for Scientific and Technological Development (CNPq) under grant 202982/2014-9. The authors acknowledge the Minnesota NMR Center and in particular Dr. Gopinath Tata for performing the Solid-state NMR experiments.
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- Lewis acids
- metal–organic frameworks