Unveiling the contribution of hexanuclear clusters for highly selective glucose conversion on Metal-Organic frameworks

With the growing demand for sustainable energy, developing new technologies based on biomass has caused deep interest. Glucose conversion into fructose is a crucial step in the sustainable biorefinery industry. Metal-organic frameworks with abundant active metal centers have shown potential, but their specific contribution is not yet fully understood. In this study, mesoporous Zr-NU-1008 with hexanuclear clusters (M6) exhibited a higher glucose conversion of 54.7 % with a fructose selectivity of 85.3 % under optimized conditions compared with its hafnium counterpart, highlighting the significance of strong Lewis acidity of metal species. By adjusting the amount of the capped formate on the hexanuclear zirconium (IV) cluster (Zr6) of Zr-NU-1008, a positive correlation with the catalytic activity was realized, suggesting the lability of the capping modulator during catalysis, which enables tuning the activity by manipulating the capping modulator. Further saturating the Zr6 cluster with the electron-withdrawing trifluoroacetate modulator achieved an excellent glucose conversion of 63.3 % with a superior fructose selectivity of 86.0 %. Besides, the recovered catalyst can be easily regenerated by reinstalling the modulator on the M6 cluster, restoring its catalytic activity.