Efficient fractionation of lignocellulosic biomass with in-situ generated diformylxylose as renewable solvent.

Development of sustainable solvents for biomass biorefining remains a pivotal challenge of green chemistry. This study presented a circular biorefining strategy that valorized hemicelluloses into biobased solvent diformylxylose (DFX; Hansen solubility parameter: 21.4 MPa-1/2) for acetal-protection pretreatment. The DFX-H2O cosolvent system (90/10, w/w), with addition of formaldehyde and HCl, showed a decent yield of acetal-protected lignin (84.7%) and enzymatic conversion of acetal-protected cellulose after deprotection by acid hydrolysis (82.9%). Crucially, hemicelluloses-derived xylose was concurrently converted into additional DFX in situ during pretreatment, sustaining the delignification process. The spent DFX (including newly formed) was effectively recovered by crystallization and the isolated acetal-protected lignin was upgraded to monomers via hydrogenolysis at near-theoretical yields (46.5%). This work demonstrates a self-reinforcing cycle where a biomass component is transformed into the key solvent enabling efficient fractionation.