Green fabrication of fully bio-based poly(vinyl alcohol)/phytic acid composite aerogels with robust 3D networks for sustainable thermal insulation and fire safety

The development of sustainable thermal insulation materials that combine light weight, high strength, and fire retardancy is essential to support global carbon neutrality goals. Herein, fully bio-based polyvinyl alcohol/phytic acid (PVA/PA) composite aerogels were fabricated through an environmentally benign refrigerator-assisted freezing process without the use of toxic solvents. The strong reactivity of bio-based phytic acid enabled the formation of a robust micro-nano three-dimensional (3D) network, yielding an aerogel with low density (0.075 g cm –3 ), high porosity (94.21%), and ultralow thermal conductivity (33.1 mW·m –1 ·K –1 ). Benefiting from its micro-nano 3D network, the aerogel exhibited excellent mechanical robustness, with compressive strength and specific modulus increasing by 125.7% and 194.5%, respectively. Due to the formation of intrinsic intumescent flame retardant (IFR) system, the aerogel achieved an extremely high limiting oxygen index (LOI) of 41.9% and a UL 94 V–0 rating (self-extinguishing time of only 1.8 s) with significantly reduced heat and smoke release during combustion. Furthermore, a solvent-free thermal chemical vapor deposition (CVD) treatment imparted durable hydrophobicity (water contact angle = 145.6°). This work provides a green and scalable strategy for producing multifunctional bio-based aerogels with great potential for high-performance and sustainable thermal insulation applications.