Bioinspired silicification of flame-retardant, thermally insulating, and robust bacterial cellulose composite aerogels.

Cellulose aerogels are promising thermal-insulation materials, but their mechanical weakness, flammability, and poor thermal stability restrict practical applications. Here, a bioinspired silicification strategy was developed to construct a bridged polysiloxane network (BPN) in situ within a bacterial cellulose (BC) framework. Density functional theory calculations revealed preferential silanol condensation, promoting the formation of a continuous BPN, while hydrogen bonding coupled the organic and inorganic networks. The resulting dual-network architecture combined interfacial reinforcement with a hierarchical porous structure, leading to a specific compressive modulus of 5.13 kN m kg-1 and reducing the room-temperature thermal conductivity from 34 mW m-1 K-1 for pristine BC to 28 mW m-1 K-1. The maximum decomposition temperature increased from 287 to 324 °C, while the char yield at 800 °C increased from 2.4% to 24.6%. Meanwhile, the peak heat release rate decreased from 106.34 to 53.21 kW m-2, corresponding to a 49.96% reduction, and the total heat release was reduced by 50.4%. Overall, the BC-BPN aerogel exhibits a competitive combination of mechanical performance, thermal insulation, and fire safety compared with previously reported cellulose-based aerogels. Moreover, a 1 cm-thick sample maintained a back-surface temperature below 50 °C during exposure to a butane flame at approximately 1300 °C. This work provides an effective strategy for developing robust, thermally insulating, and fire-safe bacterial cellulose aerogels.