π-Conjugated deep eutectic solvents enable stabilized lignin fractionation from lignocellulose and enhanced antibacterial biobased nanomaterials

Abstract

Lignin valorization is limited by intrinsic reactivity and uncontrolled aggregation during extraction, which hinder structural preservation and functionality. Here we report π-conjugated deep eutectic solvents (π-DESs) that cooperatively stabilize and assemble lignin via hydrogen bonding and π–π interactions. π-DESs enable efficient fractionation of lignocellulose at lower temperatures (60–80 °C), while preserving β-O-4 linkages and suppressing condensation. Results show that lignin dynamically integrates into a supramolecular π-stabilized solvent network that modulates its electronic environment and aggregation pathways. The extracted lignin spontaneously forms uniform micro/nano-spheres without chemical modification and exhibits excellent antibacterial activity. Meanwhile, the cellulose-rich fraction can be fibrillated into lignocellulosic nanofibrils and combined with lignin nanospheres to produce freestanding composite films with UV shielding, antioxidant, photothermal, and light-activated antibacterial functions. This work establishes π-conjugated solvent design as a strategy to couple lignin stabilization, controlled assembly, and functional materials generation.