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DOI: 10.1039/A908252B (Paper) Reference Section for: Chem. Commun., 1999, 2539-2540

Periodic mesoporous organosilicas, PMOs: fusion of organic and inorganic chemistry ‘inside’ the channel walls of hexagonal mesoporous silica

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Chiaki Yoshina-Ishii, Tewodros Asefa, Neil Coombs, Mark J. MacLachlan and Geoffrey A. Ozin

Abstract

Synthesis and characterization of new periodic mesoporous organosilicas, PMOs, containing benzene and thiophene groups ‘within’ the channel walls, is presented.

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  14. The following procedure for the synthesis of mesoporous benzenesilica is representative: bis(triethoxysilyl)benzene (0.96 g, 2.4 mmol) was added to a homogeneous solution of water (4.88 g, 0.27 mol), HCl (36%, 0.81 g, 8.1 mmol), and CPCl (0.11 g, 0.3 mmol) at ca. 32 °C, and the solution was stirred moderately for 15 min. The resulting mixture was neutralized with portionwise addition of NaHCO3 prior to adding NH4F (0.1 mg, 2.7 µmol) and aging at room temp. for two days. The powder was filtered and washed with copious amounts of water.
  15. The possibility that a mixture of amorphous organosilica and periodic mesoporous organosilica resulting from hydrolytic cleavage of the Si–C bond could give rise to the observed PXRD and NMR was addressed by examining large areas of the powder by TEM. The results of an extensive TEM study show that the PMO phase dominates over any amorphous organosilicate xerogel phase. Therefore the PMOs are responsible for both the solid state NMR and PXRD data reported here. Polarisation optical microscopy and micro-Raman spectroscopy confirm this proposal and show bridge bonded organics homogeneously dispersed throughout the PMO.7.
  16. Surfactant-free mesoporous benzenesilica shows a Type IV nitrogen adsorption isotherm at 77 K. Calculated BET suface area = 1365 m2 g–1, pore volume = 0.67 cm3 g–1, pore diameter = 2 nm, which together with PXRD–TEM d100= 3.8–3.2 nm provides a channel wall thickness ≈ 2 nm.