Isomerization of glucose to fructose catalyzed by metal-organic frameworks

The isomerization reaction of glucose to fructose was studied using five selected metal-organic frameworks (MOFs) as catalysts and a mixture of gamma-valerolactone and 10% H2O as solvent. MOFs with different metal cations (Cr3+, Al3+, Cu2+, and Fe3+) were tested between 100 and 140 degrees C. The activity tests show that the MOF with chromium yields a higher amount of fructose. A comparison between MIL-101(Cr) and MIL-53(Cr) shows a higher yield of fructose with MIL-101(Cr) (23% at 140 degrees C) in a short reaction time, due to the higher pore size of the MOF structure. The stability of this catalyst was confirmed, and it could be recycled 5 times without a significant loss of activity and exhibited an excellent fructose yield of 23-35% after 1 h of the reaction. In this work, the superior results found are due to the large porous MIL-101(Cr) catalyst combined with aprotic solvents (gamma-valerolactone-10% H2O).