Efficient and simple synthesis of B2O3-Al2O3 nanocomposites assisted by deep eutectic solvent for production of 5-hydroxymethylfurfural from glucose

The catalytic conversion of glucose to high valueadded platform chemical 5-hydroxymethylfurfural (HMF) is a promising biorefinery process, and alumina-boria catalysts are considered to be green and mild solid acid catalysts for this catalytic reaction. Here, compared to the common synthesis methods with complicated steps, we reported a simple and efficient strategy to prepare B2O3-Al2O3 nanocomposites by calcining cost-effective glucose-urea deep eutectic solvent (DES) solution containing the precursors. The prepared B2O3- Al2O3 nanocomposites exhibited an open three-dimensional skeleton and two-dimensional porous lamellar substructure, endowing them with a high specific surface area (228.27 m2/g). The introduction of boron changed the ratios of different aluminum species (AlIV, AlV, and AlVI) and borate species (BO3 and BO4), thus further affecting the acidity and the types of acid sites of the materials. The prepared B2O3-Al2O3 bifunctional acid catalysts possessing abundant Lewis acid sites and adjustable Br & oslash;nsted acid sites showed complete glucose conversion and 55.38% of HMF yield under the optimum conditions. Our study proposed a concise method to synthesize alumina-boria solid acid catalysts assisted by glucose-urea DES. We hope to extend the application and prospect of this efficient and simple synthesis strategy.