Microwave synthesis of large pored chloropropyl functionalized mesoporous silica with p6mm, Ia-3d, and Im3m structures

Chloropropyl functionalized mesoporous silicas having various mesostructural phases of hexagonal p6mm. cubic Ia-3d, and cubic Im3m have been synthesized directly via one-step co-condensation of sodium metasilicate and 3-chloropropyltrimethoxysilane (CPTS) in the presence of P123 (EO20PO70EO20) and F127 (EO106PO70EO106) triblock copolymers as structure directing agents under acidic conditions. The mesostructural phases of these mesoporous silicas were closely related to the amount of CPTS in the starting synthesis sol when P123 was used as the structure directing agent. At low concentration of CPTS (Cl/Si = 5%). a hexagonal mesostructure of SBA-15 was obtained while at higher CPTS concentrations (Cl/Si >= 7.5%). phase transformation to a bicontinuous cubic of Ia-3d phase was observed. On the other hand, the amount of CPTS did not alter the mesostructure of the materials templated by F127 structure directing agent in which the mesoporous materials having an Im3m cubic phase of SBA-16 could be synthesized from the synthesis sols with Cl/Si molar ratios as high as 20%. The successful assembly of the highly ordered chloropropyl functionalized mesoporous silicas was found to contingent upon the successful formation of chloropropyl-silicate-block copolymer micelle which was dependent on the addition sequence of the silica source, acid catalyst and CPTS. The hydrophobic chloropropyl moiety of CPTS was proposed to have penetrated into the micelle and interacted strongly with the hydrophobic PPO chain, thus controlling the overall growth of the ordered silica mesostructures. (C) 2008 Elsevier Inc. All rights reserved.