Synthesis of highly ordered mesoporous silica using cationic trimeric surfactant as structure-directing agent

Abstract

Using a cationic trimeric surfactant [C 14H 29N +(CH 3) 2(CH 2) 2N +(CH 3)(C 14H 29) (CH 2) 2N +(CH 3) 2C 14H 29]·3Br − (C 14-14-2-14), with a short spacer group ( s = 2) as structure-directing agent and sodium silicate as precursor, high quality, ordered two-dimensional (2D) hexagonal mesoporous silica was prepared through the S +I − route (S = surfactants, I = precursor). The samples were characterized by small-angle X-ray diffraction, transmission electron microscopy (TEM) and N 2 adsorption–desorption. Results showed that the pore structure belonged to 2D hexagonal structure with space group P6 mm. The mesoporous silica possessed uniform pore arrays, which pore size was about 3.0 nm. The Brunauer–Emmet–Teller (BET) surface area was up to 1000 m 2/g. With the decrease of hydrothermal temperature and of the molar ratio of sodium silicate to C 14-2-14-2-14, the mesostructure of silica became more ordered. Compared with tetradecyltrimethylammonium bromide (TTAB), which could be taken as the monomer of C 14-2-14-2-14, and it was also used as structure-directing agent to synthesize mesoporous silica, C 14-2-14-2-14 was a good structure-directing agent for the synthesis of mesoporous materials due to its strong assembly ability.