The adsorption capability of aerogels is one of their most notable characteristics, primarily attributed to their unique nanoporous network structure and exceptionally high specific surface area. The nanoporous architecture not only provides extensive molecular contact surfaces but also enables selective adsorption of specific molecules through pore size and shape.
For instance, silica aerogels exhibit superior performance in capturing organic molecules compared to traditional adsorbents such as activated carbon and silica gel. This is due to the abundance of unsaturated surface atoms on the aerogel surface, which possess high chemical reactivity, giving SiO₂ aerogels a strong tendency to adsorb various molecules—making them among the first materials applied in gas adsorption applications.
Carbon aerogels have higher specific surface areas and pore volumes than SiO₂ aerogels, reaching up to 3300 m²/g after activation, making them another major category of aerogel adsorbent materials. In filter-type gas masks, Zr(OH)₄-based fibrous aerogels can serve as highly efficient adsorbents and catalytic degradation agents. Additionally, hydrophobically modified aerogels can rapidly absorb oils in water, making them useful for cleaning up oil spills. Unmodified hydrophilic aerogels, on the other hand, effectively adsorb heavy metal ions and other harmful substances from water, enabling their application in water purification processes.
Aerogel materials also demonstrate outstanding thermal insulation properties. Among various types of aerogels, SiO₂ aerogels have been widely used in thermal insulation applications, with thermal conductivity ranging from 0.013 to 0.030 W/m·K, capable of operating within a temperature range of -200°C to 800°C, making them ideal super-insulating materials.
The thermal insulation mechanism of SiO₂ aerogels can be analyzed based on the three fundamental heat transfer modes: conduction, convection, and radiation. The three-dimensional network framework of SiO₂ aerogels consists of spherical SiO₂ nanoparticles, increasing the thermal conduction path and significantly reducing thermal conductivity. With porosity as high as 80.0%–99.9% and pore sizes smaller than the mean free path of air molecules, air movement is restricted, effectively minimizing convective heat transfer.
The pore wall structures of SiO₂ aerogels act as reflective and refractive surfaces, greatly suppressing radiative heat transfer. Moreover, SiO₂ aerogels exhibit excellent high-temperature resistance, maintaining their porous structure even at temperatures up to 900°C. Due to their non-combustible nature, they also offer superior fire-resistant properties.
Beyond SiO₂ aerogels, the thermal insulation performance of other aerogels has recently attracted growing attention, leading to an expanding range of applications. Metal oxide aerogels, such as alumina, leverage their high-temperature tolerance and chemical stability to serve as refractory insulating materials in high-temperature industrial settings. Organic aerogels, such as polyimide (PI) aerogels, feature high mechanical strength and low hygroscopicity, making them widely used in aerospace thermal insulation and fire-resistant fabrics.
In summary, aerogel materials, particularly those represented by SiO₂ aerogels, generally possess excellent thermal insulation and adsorption properties, offering broad prospects in fire prevention and firefighting applications. They can effectively isolate high-temperature sources, slow the spread of fires, and absorb hazardous chemicals and smoke during firefighting operations, thereby enhancing both efficiency and safety.