Ionic liquid-mediated facile synthesis of porous cellulose/silica aerogel composites with improved thermal insulation

Lightweight, flame-retardant biomass aerogels with recyclable property are promising for thermal insulation. To improve the thermal insulation capabilities, silica aerogel (SA) is focused due to its nanoporous microstructure and inherent material characteristics, but major challenges remain in directly dispersing it in polymers meanwhile preserving its nanoporous structure. This study reports a simple method to stably disperse SA in cellulose solution using ionic liquid (IL) through a mechanical stirring-foaming process. Then the cellulose/SA composite aerogels and aerogel fibers with high thermal insulation could be prepared followed by the regeneration process. Abandoning traditional top-to-down diffusion of regeneration bath, an innovative bottom-to-top regeneration (BtTR) technique was utilized, leading to anti-gravity diffusion of water from the bottom to top of the as-foamed cellulose/SA solution, which prevented water-induced pressure that could result collapse of air bubble. After freeze-drying, we produced SA-reinforced thermal insulation cellulose-based aerogels with uniform pore morphology (322-329 μm) and low density (∼17 mgcm⁻^³). And they also achieved a thermal conductivity of 0.034 Wm⁻^¹K⁻^¹, surpassing most reported cellulose-based aerogels (e.g., 0.039-0.045 Wm⁻^¹K⁻^¹). This study offers a new strategy to disperse SA in cellulose assisted by IL, which could be valuable for inspiring the design and construction of multifunctional aerogel materials for engineering applications.