A facile pore size controlling strategy to construct rigid/flexible silica aerogels for super heat insulation and VOCs adsorption

Silica aerogels have fascinating prospects in the field of energy-saving and environmental purification, however, it is crucial to accurately control the pore structure of aerogel so as to achieve its super heat-insulation and adsorption performance. In this work, two pore size controllable methods were proposed to construct rigid/flexible silica aerogels with an extensive range of pore size by controlling the binding modes among the gel network using methyltriethoxysilane (MTES) as silica source. With the decrease of aerogel pore size from 20.8 µm to 82 nm, the visible light transmittance of wet gel increases from 0.1 % to 34 %. Correspondingly, the thermal conductivity decreases from 0.0567 W/(m·K) to 0.0383 W/(m·K) and then increases to 0.0410 W/(m·K), maintaining a low thermal conductivity in general and showing an excellent thermal insulation and heat preservation performance. In addition, the saturation adsorption capacity of volatile organic compounds (VOCs) such as dichloromethane, dimethylformamide and hexane increases with the increase of pore size of aerogel. The proposed pore size control strategy and the relationship between the pore structure and macroscopic performance of silica aerogels are very helpful for fabricating tailored rigid/flexible silica aerogels suitable for specialized applications.