Mesoporous Aerogels Synthesized with an Ionic Liquid [Hmim]Br as Template via Ambient Pressure Drying

Abstract

Mesoporous silica aerogels with a high surface area and narrow pore size distribution were prepared from tetraethylorthosilicate (TEOS) precursor at ambient pressure by using a water miscible ionic liquid (IL) [Hmim]Br as a template. The aerogels were characterized by scanning electron microscopy (SEM) and N2 gas adsorption-desorption isotherms (BET and BJH analyses), and the effect of the IL on gel structure was also studied. The results showed that IL plays an important role in regulating the nanostructure of the aerogels, in particular, pore sizes and their distribution. By increasing the IL/Si molar ratio from 4 to 7, the specific surface area of the resultant aerogel increased from 822.38 to 992.43 m2/g, while the pore volume decreased from 1.568 to 1.031 cm3/g. More importantly, the pore size distribution became narrower with minimum average pore radius centralized at 20 nm as the IL/Si molar ratio of 7. Compared with other IL templating methods previously reported, notable attributes of this method include gelation at a much wider range of the IL/Si molar ratios (up to 7) and the formation of homogeneous porous structure whose size can be up to meso-scale (2 nm - 50 nm).