Bioinspired Lignocellulose Foam: Exceptional Toughness and Thermal Insulation

The biofoam exhibits significant advantages in environmental and sustainability aspects as an effective alternative to petrochemical foams; however, its limited mechanical stability seriously hinders its practical application. Herein, a synergistic strategy combining structural bionics and supramolecular cross-linking is proposed to fabricate a biodegradable lignocellulosic biofoam featuring a "pillar-spacer" microlattice texture, utilizing multiscale cellulose fibers (CFs) and sodium lignin sulfonate (SLS) as inspiration from the natural cuttlebone. Attributed to the robust interfacial bonding between nanoscale cellulose and SLS, akin to "rebar and cement", complemented by the mechanical support from cellulose microfibers, the CFs/SLS biofoam with a low density of 62 mg cm-3 exhibits a compression modulus of 6.56 MPa, nearly four times higher than that of the CF biofoam (1.67 MPa). Additionally, it exhibits excellent thermal insulation, boasting a remarkably low thermal conductivity of 0.046 W m-1 K-1, outperforming recently reported biofoams and plastic foams. Moreover, integrating a functional SiO2 nanocoating results in the SiO2@CFs/SLS foam, which delivers satisfactory flame retardation and smoke inhibition without compromising the mechanical strength or thermal insulation. This work highlights the potential for developing sustainable, eco-friendly, and mechanically robust biofoams for practical applications.