Enhanced glucose conversion to formic acid with deep eutectic solvents-mediated bimetallic oxides: Morphology and valence state regulation

Abstract

The valorization of biomass into chemicals has emerged as an appealing approach for utilizing biomass as a renewable feedstock. In this study, a deep eutectic solvent (DES)-mediated solvothermal strategy was employed to synthesize a bimetallic nanoparticle catalyst for the conversion of glucose to formic acid. The impact of DES-based solvent systems on the morphology, valence states, and catalytic performance of the catalyst were systematically examined. Experimental results demonstrated that at the same reaction conditions (150 °C, 3 h), the catalyst prepared using DES achieved a formic acid yield of 63.63 %, significantly surpassing the 50.37 % yield obtained with catalysts synthesized through conventional hydrothermal methods. Under optimal conditions of reacting at 150 °C for 5 h, maximum formic acid yield of 65.17 % was attained with DES-mediated catalyst. Characterization underscored the crucial role of DES in promoting the construction of uniform nanospheres and in reducing the manganese valence state from +2.69 to +2.30, which serves as the primary active site. Mechanistic studies identified two main pathways governing the glucose-to-formic acid conversion: (i) a direct conversion route from glucose to formic acid and (ii) an initial isomerization of glucose to fructose, followed by the conversion of fructose into formic acid.