Fabrication of Silica Monoliths with Hierarchically Porous Structure from Freeze-Drying

Abstract

This paper provides a novel route to prepare silica monoliths with hierarchical porous structure via freeze drying. In this method, macroporous silica monoliths were first produced by freeze-drying and calcination. By adjusting the concentration of cetyltrimethylammonium bromide in ethylsilicate, a layer of mesoporous thin film was attached on the macroporous silica monolith. The structural characterization of the hierarchical porous monoliths were studied by field emission scanning electron microscopy, mercury porosimeter and nitrogen adsorption-desorption techniques (BET). It turned out that the pore distribution of the obtained monoliths was ranged from 3.72 nm to 23.21nm and the maximum specific surface area calculated from BET was about 288 m2/g, which indicated the existence of hierarchical structure in the obtained material.