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

Using a cationic trimeric surfactant [C14H29N+(CH3)2(CH2)2N+(CH3)(C14H29) (CH2)2N+(CH3)2C14H29]·3Br− (C14-14-2-14), 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 N2 adsorption–desorption. Results showed that the pore structure belonged to 2D hexagonal structure with space group P6mm. 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 m2/g. With the decrease of hydrothermal temperature and of the molar ratio of sodium silicate to C14-2-14-2-14, the mesostructure of silica became more ordered. Compared with tetradecyltrimethylammonium bromide (TTAB), which could be taken as the monomer of C14-2-14-2-14, and it was also used as structure-directing agent to synthesize mesoporous silica, C14-2-14-2-14 was a good structure-directing agent for the synthesis of mesoporous materials due to its strong assembly ability.