(535f) Selective Glucose to Fructose Isomerization over Modified Zirconium UiO?66 in Alcohol Media

Biomass-derived feedstocks are alternative carbon sources to fossil fuels to produce value-added chemicals. Glucose isomerization to fructose is a key reaction for the conversion of sugars into these platform chemicals such as 5-hydroxymethylfurfural (HMF). Despite the use of zeolites as Lewis-acid catalysts for glucose isomerization, metal-organic frameworks (MOFs) have drawn attention due to their high tunability and density of active sites. In this work, we used a modified zirconium UiO-66, a highly stable MOF, as a catalyst for glucose isomerization reaction in alcohol media. The fructose selectivity is shown to change depending on solvent choice drastically. A combined effect of adsorption and solvation leads to the formation of alkyl-glucosides in depletion of fructose when methanol or ethanol are used. The use of 1-propanol as a solvent leads to selectivities of 72 % and 10 % in fructose and mannose, respectively at 82 % glucose conversion. We also demonstrate by ¹³C NMR that the sugars adsorb onto UiO-66 in a closed form and that fructose is formed by an intramolecular C2-C1 hydride transfer mechanism.

[1] Dorneles de Mello, M.; Tsapatsis, M. ChemCatChem 10.1002/cctc.201800371.