Synthesis of high-quality MCM-48 mesoporous silica using cationic Gemini surfactant C12-2-12

At mild conditions, high-quality ordered cubic mesoporous silica (space group 1a3d) has been prepared using Gemini surfactant [C12H25N-(CH3)(2),-(CH2)(2)-N-'(CH3)(2)-C12H25] (.) 2Br(-) (denoted as C12-2-12) with a short spacer as structure-directing agent and sodium silicate as precursor. The samples were characterized by X-ray diffraction and N-2 adsorption-desorption technique. Results showed that the resulting mesoporpous silica had a MCM-48 structure. Type IV isotherm occurred in nitrogen adsorption-desorption curves,which indicated that the pore size of the resulting silica was in the range of mesopore. The ordering of pore structure decreased with the increase of the molar ratio of ethyl acetate to sodium silicate. The high-quality cubic mesoporous structure was easily formed at a molar ratio of ethyl acetate/sodium silicate of 2:1, and the formation mechanism was explained according to the theory of the packing parameter of surfactants. (C) 2004 Elsevier B.V. All rights reserved.