Yi Duan, Shangzhong Zhang, Lifeng Yan
Lignocellulosic biomass is an abundant, renewable, and environmentally benign resource that can be catalytically converted into valuable bio-based feedstocks and high-value chemicals through appropriate processes. However, achieving such transformation through environmentally benign and efficient routes remains a significant challenge. In this study, we demonstrate a fully green solvent system composed of a zinc chloride–choline chloride deep eutectic solvent (DES) combined with ethyl acetate to form a biphasic system, which enables the direct one-pot conversion of corncob biomass after a brief microwave-assisted pretreatment under remarkably mild conditions (atmospheric pressure and 90 °C). A high furfural yield of up to 86.5% was achieved via the selective degradation of hemicellulose, while cellulose remained largely unconverted and ultimately enabled the isolation of cellulose and lignin with high contents in the biphasic system. Simultaneously, effective fractionation of lignocellulosic components was achieved, with a lignin removal rate of 78.1%. To the best of our knowledge, there are very limited reports achieving such a high furfural yield directly from lignocellulosic biomass under such mild conditions. Most conventional and recently reported systems typically require elevated temperatures (160–240 °C) to obtain moderate to high furfural yields. The separated cellulose retained high crystallinity, and 2D-HSQC NMR analysis revealed well-preserved characteristic structural units in the extracted lignin, indicating that its fundamental framework was largely maintained. Furfural was predominantly extracted into the ethyl acetate phase, and the low boiling point of ethyl acetate significantly facilitated downstream separation. In addition, the DES exhibited excellent recyclability, maintaining over 80% of the furfural yield after more than five reuse cycles, highlighting its considerable economic potential.