Different neutral surfactant template extraction routes for synthetic hexagonal mesoporous silicas

Abstract

The co-condensation of a tetraethoxysilane molecule on a neutral n-octylamine surfactant template is a convenient synthetic methodology for mesostructured material preparations. Distinct routes of template removal were investigated. The neutral surfactant was removed by calcination, hot solvent extraction, heating at 150 °C, in vacuo at room temperature and at 100 °C, and air drying, with the products assigned as HMM, HMS, HME, HMV1, HMV2 and HM, respectively. ²⁹Si NMR, infrared, surface area, pore diameters and pore volume determinations were employed to characterize each sample. Elemental analysis detected the presence of amine residues of 1.8, 1.2, 0.2, 1.6 and 0.30 mmol g⁻¹ for HMA, HME, HMS, HMV1 and HMV2, respectively. The HMM, HMS and HMV2 samples presented a low amount of amine residues, and HMS and HMV2 have the great advantage of permitting template removal without calcination.