Microwave-hydrothermal synthesis and characterization of microporous–mesoporous disordered silica using mixed-micellar-templating approach

Abstract

The present investigation reports a mixed micellar supramolecular templating approach to obtain microporous–mesoporous silica frameworks having textural characteristics close to supermicroporous frameworks under microwave-hydrothermal conditions. The crystallization of such frameworks was achieved by templating a silica precursor with a mixed micellar system, comprising of pluronic123 copolymer (EO 20PO 70EO 20; M.W. 5800) and cationic surfactants (n-Decyltrimethyl ammonium bromide/Dodecyltrimethyl ammonium bromide/Hexadecyltrimethyl ammonium bromide) at 373 K. The crystallized materials were characterized by means of powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), and nitrogen adsorption measurements at 77 K. Furthermore, the existence of supramolecular templating phenomenon in the formation of porous silica was established by performing the crystallization in the presence of a swelling agent (mesitylene). The X-ray diffraction patterns for calcined samples exhibited low angle peaks with interplanar spacings in the range of 2.7–3.2 nm. The specific BET surface area values for various samples, based on nitrogen adsorption data, were found to be in the range of 740–953 m 2 g −1 whereas pore volumes for the crystallized samples were found to vary in the range of 0.35–0.52 cm 3 g −1.