The visible-light mediated selective photo-oxidation of glucose using unmodified TiO2 as a catalyst is reported for the first time. The effect of the catalyst to substrate ratio, lamp power and TiO2 crystalline phases on the conversion and product distribution under both visible and UVA light is explored. Higher conversions were obtained under UVA light but as a result of substantial mineralization through an unselective pathway. Optimization of the reaction conditions resulted in 42% glucose conversion under visible light with 7% selectivity to gluconic acid and 93% selectivity to other partial oxidation products with the total suppression of a mineralization pathway to CO2. It is also shown that selective glucose conversion can occur under natural sunlight light after 7h exposure. In this systematic study, we prove that it is indeed possible to use TiO2 as a photocatalyst to upgrade biomass derivatives selectively by tailoring the reaction conditions. Most importantly, we find the ligand-to-metal charge-transfer effect as a result of glucose adsorption to the surface of TiO2 determinant in the photo-activity observed under visible light irradiation. Knowledge of this effect along with the careful control of reaction conditions means that the selective photo-catalytic conversion of other biomass derived carbohydrates under visible light is a viable route to higher value chemicals

The visible‐light‐mediated photo‐catalytic selective valorisation of glucose using TiO₂‐supported Ag nanoparticles is shown for the first time. The optimisation of the catalyst composition, substrate‐to‐catalyst ratio and reaction medium proved that a near total suppression of the mineralisation pathway could be achieved with a selectivity to partial oxidation products and small‐chain monosaccharides as high as 98 %. The primary products were determined to be gluconic acid, arabinose, erythrose, glyceraldehyde and formic acid. Under UVA light, the selectivity to organics decreases because of the production of CO₂ from mineralisation. A reaction mechanism is proposed based on an α‐scission process combined with the Ruff degradation reaction, which explains the presence of the oxidation products, the smaller carbohydrates and formic acid. X‐ray photoelectron spectroscopy, UV/Vis spectroscopy and microscopy studies showed the presence of plasmonic 4 nm particles of silver that were oxidised to silver oxide over the course of the reaction, and recycling studies revealed that this was not detrimental to activity.

The selective production of p-xylene and other aromatics starting from sugars and bioderived ethylene offers great promise and can eliminate the need for separation of xylene isomers, as well as decreasing dependency on fossil resources and CO₂ emissions. Although the reaction is known, the microporosity of traditional commercial zeolites appears to be a limiting factor. In this work, we demonstrate for the first time that simply desilication of microporous commercial zeolites by a simple NaOH treatment can greatly enhance conversion and selectivity. The [4 + 2] Diels–Alder cycloaddition of 2,5-dimethylfuran with ethylene in a pressurised reactor was investigated using a series of H-ZSM-5 catalysts with SiO₂/Al₂O₃ ratios 30 and 80 with increasing pore size induced by desilication. X-ray diffraction, scanning electron microscopy, ²⁷Al magic-angle spinning nuclear magnetic resonance, temperature programmed desorption of ammonia, and nitrogen physisorption measurements were used to characterise the catalysts. The enhancement of conversion was observed for all desilicated samples compared to the untreated zeolite, and increases in temperature and ethylene pressure significantly improved both dimethylfuran conversion and selectivity to p-xylene due to the easier desorption from the zeolite’s surface and the augmented cycloaddition rate, respectively. A compromise between acidity and mesoporosity was found to be the key to enhancing the activity and maximising the selectivity in the production of p-xylene from 2,5-dimethylfuran.