Organic-inorganic hybrid chitosan-based adhesive combined with Cu/ZIF-8 to construct wood composites with flame retardant properties.

The application of biopolymers in adhesive design holds immense potential for advancing the sustainable manufacturing of high-performance materials. In this study, chitosan (CS), a renewable and biodegradable biopolymer, serves as the structural backbone for developing an innovative organic-inorganic hybrid resin Cu/ZIF-8@CS-MCS@BN. Initially, CS was chemically functionalized via crosslinking with maleic anhydride (MA) to form a maleated chitosan network (CS-MCS), exploiting the biopolymer's abundant amino and hydroxyl groups for covalent bonding. This chitosan-based network was subsequently reinforced with boron nitride nanosheets (BN) and copper-doped ZIF-8 metal-organic frameworks (Cu/ZIF-8), synergistically combining the flame-retardant and mechanical-enhancing properties of inorganic fillers with the organic network of the chitosan matrix. The Cu/ZIF-8@CS-MCS@BN resin was processed into two distinct wood composites: (1) plywood fabricated by hot-pressing poplar veneers with the resin exhibited exceptional interfacial adhesion, achieving a boiling-water-resistant shear strength of 1.01 MPa, which surpasses the requirements of the Chinese national standard GB/T 9846-2015; (2) lightweight aerogels prepared by freeze-drying resin-wood flour mixtures demonstrated outstanding compressive resistance (compressive modulus: 45.23 MPa) and fire safety (limiting oxygen index (LOI) = 42.8 %, UL-94 V-0 rating). This work establishes a green paradigm for fabricating multifunctional wood composites, highlighting the pivotal role of biopolymer engineering in next-generation construction materials.