Catalytic valorisation of d-fructose and alcohols using silica–PEI–polyoxometalate composites

A nano-catalyst composed of polyoxometalates (POMs) ionically immobilized on polyethyleneimine (PEI) functionalized silica (SiO₂–[PEIH]_x[POM]) was used for the dehydration of D-fructose to 5-hydroxymethylfurfural (HMF) and the subsequent oxidation of HMF to 2,5-diformylfuran (DFF). The morphology and textural properties of silica supports, SBA-15 and Stöber nanoparticles, influenced the catalytic outcome. SiO₂–[PEIH]_x[POM] demonstrated high thermal stability and exceptional catalytic activity in fructose transformation. Using DMSO as solvent in a one-pot synthesis, we achieved an HMF yield of 95% after 0.5 hours at 150 °C and a DFF yield of 69% after 20 hours, whereas HMF oxidation afforded a DFF yield of 86% under the same conditions with a considerable turnover number (TON) of 1720. These findings suggested that SiO₂–[PEIH]_x[POM] catalysts are promising candidates for the valorization of fructose into sustainable chemical sources.