Dual-functional 3-aminobenzenesulfonic acid additive enhances cellulose pretreatment in DMSO-rich ionic liquid systems.

Ionic liquids (ILs) are effective agents for cellulose pretreatment but are hindered by high cost and high viscosity. While dilution with dimethyl sulfoxide (DMSO) reduces IL viscosity and consumption, high DMSO content (IL/DMSO ≤4:6, w/w) reduces pretreatment efficacy. Herein, 3-aminobenzenesulfonic acid (ABS) was introduced as an additive to enhance pretreatment efficiency within a 1-allyl-3-methylimidazolium chloride ([Amim]Cl)-DMSO system (4:6, w/w). ABS operates through two mechanisms: (1) binding to [Amim]+ to release Cl- (Proven by 1H and 35Cl NMR spectroscopy, ESI-MS, and molecular dynamics simulations.), thereby facilitating the disruption of cellulose inter- and intramolecular hydrogen bonds; and (2) promoting β-1,4-glycosidic bond cleavage via its sulfonic acid group, thereby reducing the cellulose degree of polymerization (DP). Adding ABS reduced the crystallinity and DP of regenerated cellulose while increasing its specific surface area and hydrophobicity. Consequently, cellulose enzymatic hydrolysis performance improved significantly. Compared to the baseline [Amim]Cl-DMSO system (initial rate: 2.18 mg/(L·min) and 144 h glucose yield: 25.11%), the addition of 1.2 wt% ABS increased these values to 7.69 mg/(L·min) and 97.32%, respectively. Adding ABS also markedly enhanced corn straw pretreatment efficiency in high-DMSO-content IL-DMSO systems, representing an approach for designing green, efficient, and economical ionic liquid pretreatment systems.