A multifunctional ionic liquid-biphasic strategy for balanced utilization of cellulose, hemicellulose and lignin in...

An integrated biorefinery strategy for the comprehensive valorization of sugarcane bagasse was developed using a sulfonic acid-functionalized ionic liquid, 1-butyl-3-methylimidazolium benzene sulfonate ([C₄SO₃Hmim][PhSO₃]), in a ternary biphasic solvent system. By coupling the strong Brønsted acidity of the ionic liquid with solvent-regulated phase separation, efficient fractionation and selective conversion of lignocellulosic components were achieved. Aprotic cosolvents, particularly γ-valerolactone (GVL), effectively modulated reaction pathways, enabling high xylose conversion (∼80%) with furfural selectivities of 74.8-79.8% while suppressing side reactions. Under optimized GVL/H₂O/MIBK conditions, a furfural yield of 71.5% was obtained at 150 °C, accompanied by efficient delignification (82.5%) and high cellulose retention (74.7%). Structural analyses confirmed the selective cleavage of lignin-carbohydrate complex linkages and β-O-4 ether bonds while preserving the aromatic backbone of lignin. Density functional theory calculations revealed that strong hydrogen bonding and van der Waals interactions between the ionic liquid and a lignin-carbohydrate model compound weakened inter-component linkages, providing molecular-level evidence for the experimentally observed enhancement in lignin removal and biomass fractionation efficiency. The cellulose-rich residues exhibited excellent enzymatic digestibility, achieving a glucose yield of 91.6%, while the recovered lignin showed increased phenolic hydroxyl content and improved antioxidant activity. Overall, the tunable ionic liquid-biphasic system enabled efficient and balanced utilization of hemicellulose, cellulose, and lignin, while providing mechanistic insight into solvent-regulated biomass fractionation for integrated biorefinery applications.