Truss-inspired ultra-high strength, fire-safe, and thermal insulating double-crosslinked wood aerogels

Bio-based wood aerogel is one of the most promising materials to replace traditional petrochemical-based insulation materials. However, the flammability and poor mechanical strength of bio-based wood aerogels limit their applications in emerging fields. Inspired by a truss-supporting system, this study prepared a multifunctional bio-based cross-linked wood aerogel (TSP@Ca) by a dual hydrogen-ionic bonding strategy involving an oxidized wood cellulose framework, sodium alginate, phytic acid (PA), and Ca²⁺. Finite element simulation and mechanical analysis indicated that the multi-point support structure, resembling a truss framework, formed in the oxidized wood template significantly improved the strength of TSP@Ca aerogel (9.99 MPa), with a 154.84% enhancement relative to that of oxidized delignified wood (TODW). The limiting oxygen index of TSP@Ca3 aerogel was as high as 43.3%, and it can extinguish immediately when the fire was removed. The introduction of PA and Ca²⁺ promoted the dehydration, cross-linking, and charring of TSP@Ca aerogel, while the produced phosphorus-containing free radicals played an inhibitory role in the gas phase. Therefore, the peak of heat release rate of TSP@Ca aerogel was 80.66% lower than that of TODW, showing excellent fire safety. Benefiting from the complex heat conduction path and enhanced interface resistance, the thermal conductivity of TSP@Ca was 46.4% lower than that of TODW. The resulting aerogel combines ultra-high mechanical strength, excellent fire resistance, and thermal insulation, aligning with “green” development goals and offering broad application potential in construction, rail transport, and new energy sectors.