A Periodic DFT Study of Glucose to Fructose Isomerization on Tungstite (WO3•H2O): Influence of Group IV-VI Dopants and Cooperativity with Hydroxyl Groups

Periodic density functional theory (DFT) calculations were carried out to investigate the mechanism of glucose to fructose isomerization over tungstite (WO3 center dot H2O). The isomerization reaction is catalyzed by undercoordinated W6+ sites. The reaction mechanism proceeds through an H-shift from C2 to Cl and involves a cooperative action of Lewis acidic tungsten sites with neighboring proton donors, which form a hydrogen-bonding surface network. Dopants of group IV-VI transition metals stabilize the preactivated complex, which is the deprotonated open form of glucose adsorbed to the surface. In particular, calculations reveal that doping the tungstite structure with Nb5+ and Ti4+ ions is effective in lowering the overall barrier for glucose isomerization.