Construction of lignin–metal polyphenol networks and their application in smart paper-based active packaging: Multifunctional materials with both antioxidant and UV-shielding functions

Facing the urgent need for sustainable and functional food packaging, developing high-performance materials from natural polymers is crucial. Herein, we propose a green strategy inspired by crustacean exoskeletons to construct lignin–metal polyphenol networks (L-MPNs) via proton-based ionic liquid pretreatment and metal-ion coordination. This forms a stable 3D network utilizing lignin's phenolic hydroxyl groups, which significantly enhances antioxidant activity, achieves >99% UV shielding, and exhibits 92.5% DPPH radical scavenging capacity. Applied to paper packaging, Ferric-ion-coordinated lignin-metal polyphenol networks (FL-MPNs, 100 g/m 2 ) impart excellent barrier and antioxidant properties alongside maintained mechanical strength, cutting water vapor transmission by ∼40%. In freshness tests, they reduced mass loss to 3.52% and pH change to 0.17, effectively inhibiting food deterioration. Thus, FL-MPNs advance lignin valorization for next-generation sustainable smart packaging to ensure safer, more stable food preservation.