Novel carbonaceous catalysts for the conversion of glucose to 5-hydroxymethylfurfural and levulinic acid under microwave irradiation: Experimental and mechanistic-theoretical studies

Achieving an excellent yield of 5-hydroxymethylfurfural (5-HMF) and levulinic acid (LA) through the direct, one-pot catalytic conversion of glucose remains a challenge, making the synthesis of a low-cost, bifunctional, sustainable heterogeneous catalyst critical. In this work, amorphous carbon-containing Brønsted – Lewis acid sites and dimethyl sulfoxide (DMSO) were utilized to perform a one-pot direct conversion of glucose into 5-HMF and LA using domestic microwave irradiation. Under one-pot conditions, combining acidic Brønsted–Lewis sites enables the direct preparation of 5-HMF and LA from glucose via isomerization, dehydration, and water addition. The influences of solvent, heating techniques, reaction time, and catalyst loading on the process were studied thoroughly. The optimized conditions (reaction time of 20 min under the microwave power of 80 W) resulted in 5-HMF and LA yields of 26.7% and 29.3%, respectively, with the glucose conversion of nearly 90% in DMSO solvent. Furthermore, the catalyst could be quickly recovered, but the reusability of the recovered catalyst was limited. To gain a deeper understanding and explore further applications, density functional theory (DFT) and statistical mechanical calculations were conducted to elucidate the comprehensive mechanism of glucose transformation into 5-HMF. This work demonstrates a simple microwave-assisted strategy for sustainable glucose valorization using a low-cost bifunctional catalyst, offering a practical approach toward integrated biomass conversion.