Photoassist-phosphorylated TiO₂ as a catalyst for direct formation of 5-(hydroxymethyl)furfural from glucose

Photo-assisted phosphorylation of an anatase TiO₂ catalyst was examined to improve its catalytic performance for the direct production of 5-(hydroxymethyl)furfural (HMF), a versatile chemical platform, from glucose. In phosphorylation based on simple esterification between phosphoric acid and surface OH groups on anatase TiO₂ with water-tolerant Lewis acid sites, the density of phosphates immobilized on TiO₂ is limited to 2 phosphates nm^-2, which limits selective HMF production. Phosphorylation of the TiO₂ surface under fluorescent light irradiation increases the surface phosphate density to 50%, which is higher than the conventional limit, thus preventing the adsorption of hydrophilic glucose molecules on TiO₂ and resulting in a more selective HMF production over photoassist-phosphorylated TiO₂.