Facile synthesis and morphology control of highly ordered cubic mesoporous silica SBA-1 using short chain dodecyltrimethylammonium chloride as the structure-directing agent

Abstract

We presented a facile synthesis route for the formation of highly ordered cubic mesoporous silicas SBA-1 ( Pm3n mesophase) with rich morphologies over a broad synthesis temperature range and synthesis compositions by using dodecyltrimethylammonium chloride (C 12TMACl), a surfactant with a relatively short alkyl chain as compared to the conventional C 16TMABr often used for the synthesis of the M41S materials, as the template under strongly acidic conditions. Various synthesis parameters such as HCl concentration, synthesis temperature, and surfactant concentrations were systematically investigated. The materials thus obtained were characterized by a variety of techniques including powder X-ray diffraction (XRD), solid-state 29Si nuclear magnetic resonance (NMR) spectroscopy, scanning electron microscopy (SEM), and nitrogen sorption measurements. It was found that increasing the synthesis temperature and HCl concentration during the synthesis not only enhanced the cross-linking degree of silica framework, as revealed by 29Si magic angle spinning (MAS) NMR, but also prevented the undesirable phase transformation that was often observed in the conventional synthesis of pure silica SBA-1. By controlling the synthesis temperature and compositions, rich morphologies (cubic, octadecahedron, spherical, edged-truncated cube) of the SBA-1 particles can be obtained.