Incorporation of MgO into nitrogen-doped carbon to regulate adsorption for near-equilibrium isomerization of glucose into fructose in water

Abstract

Glucose isomerization to fructose is an essential step for biomass valorization, but implementing this reaction via chemocatalysis suffers from low reaction efficiency and inferior catalyst reusability. Herein, MgO was incorporated into nitrogen-doped carbon via pyrolysis of ZIF-8 with MgCl2 to synchronously enhance the catalytic performance and stability. The resultant MgO/NC-700 catalyst gave fructose yields of 42.9 % and 40.8 % at glucose loading of 10 and 20 wt%, respectively, approaching to the upper limit of reaction equilibrium. The average fructose productivity was 0.2267 mmol g−1 h−1, more than 2.29 times higher than the state-of-the-art heterogeneous catalysts. Moreover, the catalyst showed good stability and reusability without complicated regeneration steps. Isotope labelling study by NMR spectra revealed that the reaction is mainly proceeded via proton transfer mechanism. Both static adsorption experiment and DFT calculation indicated that the shift of reaction equilibrium towards fructose is due to the preferential adsorption of glucose.