Regulating Lewis acid-based sites on carbon nitride for selectivity conversion of glucose to mannose and fructose in water

Mannose exhibits specific biological functions and can be acted as a precursor for many drugs. In this study, we used glucose as substrate for preparing mannose by thermos-chemical synthesis. Carbon nitride (C3N4) supported molybdenum and aluminum was prepared to selectively convert glucose to mannose and fructose in water. Results show that the yield and selectivity of mannose from glucose are 31.47 % and 85.00 %, respectively, at 130 °C for 5 min by C3N4 supported molybdenum (Mo-C3N4). The catalytic efficiency of Mo-C3N4 shown to be high. The yields of mannose and fructose are 18.72 % and 41.34 %, correspondingly and the Al-Mo-C3N4 exhibits a total selectivity of 91.91 % for mannose and fructose. C3N4 provided Brønsted bases (N-containing groups) facilitate isomerization of glucose to fructose. The Mo-C3N4 characterizations reveal that the 2D nanosheet structure embeds Mo species (MoO2, MoO3 and MoC2) at a size of 5–10 μm. The characterizations of Al-Mo-C3N4 proved the hierarchically porous structure and the homogeneous distributions of Al species (Al 2 O 3 ) and Mo species (Mo 4+ and Mo 6+ ) throughout the C3N4 skeletons. The work reveals a green and low-cost catalyst based on C3N4 support for highly selectivity catalyzing the conversion of glucose to mannose and fructose in aqueous.