Structural characterization of organically-modified porous silicates synthesized using CTA+ surfactant and acidic conditions

Abstract

Organically-modified silicates have been synthesized from RSi(OEt) ₃ (R=CH ₃ , C ₂ H ₅ , C ₈ H ₁₇ , CH ₂ =CH or C ₆ H ₅ ) and TEOS under acidic conditions, in the presence of cetyltrimethylammonium bromide (CTAB). The introduction of RSiO _1.5 units with R/Si=0.2:1, prevents the system from adopting a high degree of hexagonal mesostructural order, except when R=C ₆ H ₅ . For the sample containing the phenyl functionality, removal of the surfactant by calcination at 350°C appears to be more complete, and less disruptive to mesoscopic ordering than solvent extraction using EtOH. Nitrogen adsorption measurements on the hexagonally ordered calcined sample that still contains phenyl groups, yields a type I isotherm, typical of a microporous solid with a pore size distribution centered at 15 Å.