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Biomass-derived sustainable film is a promising alternative to synthetic plastic, but hampered by strength, toughness and flexibility trade-off predicament. Here, a feasible and scalable strategy was proposed to fabricate strong and flexible lignocellulosic film through molecular reconstruction of cellulose and lignin. In this strategy, polyphenol lignin was absorbed and wrapped on the surface of cellulose fiber, forming strong interfacial adhesion and cohesion via intramolecular and intermolecular hydrogen bonding. Further, covalent ether bond was generated between the hydroxyl groups of lignocellulose to form chemical cross-linking network induced by epichlorohydrin (ECH). The synergistic effect of hydrogen bonding and stable chemical cross-linking enabled the resultant lignocellulosic film (ELCF) with outstanding mechanical strength of 132.48 MPa, the elongation at break of 9.77 %, and toughness of 9.77 MJ·m -3 . Notably, the integration of polyphenol lignin synergistically improved the thermal stability, water resistance, UV-blocking performances of ELCF. Importantly, after immersion for 30 d, ELCF still possessed high wet strength of 70.38 MPa, and elongation at break of 7.70 %, suggesting excellent and durable mechanical performances. Moreover, ELCF could be biodegraded in the natural soil. Therefore, this study provides a new and versatile approach to reconstruct highly-performance lignocellulosic films coupling strength, toughness with flexibility for promising plastic replacement., Competing Interests: Declaration of competing interest The authors declare no conflicts of interest., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Due to the complexity, heterogeneity and recalcitrant structure of lignin, the extraction of multifunctional lignin directly from lignocellulose is still a challenge. Here, a green and recyclable route was proposed to separate high-quality lignin and tailor its functionalities. Through tuning the components of deep eutectic solvent (DES) and separation procedures, DES extracted lignin (DESL) exhibited high purity of 99.6 %, yield of 83.2 % and phenolic hydroxyl content of 8.33 wt%. The results of FTIR and 13 C NMR demonstrated that DESL possessed more oxygen-containing reactive groups compared with commercial lignin (CL), enabling DESL with more superior functional activities. DESL exhibited higher antioxidant activity with the DPPH capture rate of 73.2 %. Meanwhile, DESL showed strong bactericidal effects against E. coli (100 %) and S. aureus (100 %) due to higher phenolic hydroxyl content, which could destroy bacterial cell membranes and inhibit bacterial metabolism by interacting with phospholipid layer and protein. Additionally, DESL displayed strong UV absorption and could be blended with polyurethane to enhance UV shielding property of polyurethane composite film with >50 of UPF value. In summary, DES treatment is a suitable strategy for high-quality lignin separation, which opens a broad spectrum of possibilities for lignin valorization., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)