All-biomass-based material with tunable mechanical and optical properties fabricated by multiscale cellulose and...

Deep eutectic solvents (DESs) have shown remarkable promise in biomass separation owing to their exceptional lignin solubility. In this work, we present a streamlined method for producing all-biomass-based materials that eliminates the need for energy-intensive lignin regeneration and DES recovery processes. By precisely modulating cellulose-lignin interactions through DES, we demonstrate tunable control over material properties. Results show that increasing lactic acid (LA) concentration in DES suppresses the degradation of lignin's carbon-carbon bonds while promoting partial cleavage of syringyl (S) units. This results in lignin enriched with phenolic hydroxyl groups, which strengthens hydrogen bonding with cellulose and enhances lignin-cellulose adhesion. These synergistic interactions produce an all-biomass pulp material with exceptional mechanical performance: a tensile strength of ∼32 MPa and a Young's modulus of ∼5445 MPa, significantly surpassing those of pure cellulose pulp (9 MPa and 1455 MPa, respectively). Furthermore, the homogeneity and UV shielding performance of these membranes improves with smaller lignin molecular weights, a higher number of phenolic hydroxyl groups in the lignin structure, or coarser cellulose fibers. This work not only advances the high-value utilization of lignocellulosic biomass but also simplifies production workflows, providing an innovative strategy for designing advanced, fully sustainable biomass-based materials.