Hierarchically porous tantalum oxide as a high-performance catalyst for efficient conversion glucose to HMF

Abstract

Efficient conversion of glucose into 5-hydroxymethylfurfural (HMF) is an important reaction for the valorization of carbohydrate-based biomass towards the synthesis of high-value platform chemicals. However, the design of water-tolerant catalysts with superior efficiency still remains a substantial challenge. In this work, hierarchically porous tantalum oxide was synthesized via a sol-gel process accompanied by phase separation. Subsequent calcination at temperatures exceeding 600 °C induced crystallization of the tantalum oxide xerogel, leading to the formation of both Lewis and Brønsted acid sites. Electron spin resonance (ESR) analysis revealed that the acid sites originated from oxygen vacancies, characterized by a relatively low molar formation enthalpy (ca. 25 kJ/mol). The resulting tantalum oxide exhibited excellent thermal stability and excellent water tolerance under aqueous reaction conditions. Remarkably, the catalyst afforded a 70.8% HMF yield with 96.5% selectivity from a 1.0 wt.% glucose solution, and an high HMF productivity of 8.0×10 -2 mol h -1 kg-solution -1 from a 20.0 wt.% glucose solution, under mild conditions of 170 °C in a water-MIBK biphasic system. This excellent catalytic performance highlights the strong potential of the tantalum oxide material for practical and scalable HMF production.