Li-promoted C3N4 catalyst for efficient isomerization of glucose into fructose at 50 °C in water

Efficient and selective glucose-to-fructose isomerization is a crucial step for production of oxygenated chemicals derived from sugars, which is usually catalyzed by base or Lewis acid heterogeneous catalyst. However, high yield and selectivity of fructose cannot be simultaneously obtained under mild conditions which hamper the scale of application compared with enzymatic catalysis. Herein, a Li-promoted C3N4 catalyst was exploited which afforded an excellent fructose yield (40.3 wt%) and selectivity (99.5%) from glucose in water at 50 °C, attributed to the formation of stable Li–N bond to strengthen the basic sites of catalysts. Furthermore, the so-formed N6–Li–H2O active site on Li–C3N4 catalyst in aqueous phase changes the local electronic structure and strengthens the deprotonation process during glucose isomerization into fructose. The superior catalytic performance which is comparable to biological pathway suggests promising applications of lithium containing heterogeneous catalyst in biomass refinery.