B. Boury et al., Hybrid organic-inorganic xerogel access to meso- and microporous silica bythermal and chemical treatment, CHEM MATER, 11(2), 1999, pp. 281-291
Hybrid xerogels of general formula (O)(1,5)Si-C=C-(CH2)(n)-C=C-Si(O)(1,5) w
ere prepared by sol-gel polycondensation in THF of the corresponding precur
sors (H3CO)(3)Si-C=C-(CH2)(n)-C=C-Si(OCH3)(3), without catalyst. Treatment
of the hybrid xerogels was with methanol and water in the presence of 2.0%
of ammonium fluoride as catalyst. For 2 < n < 4, elimination of the organic
spacer was quantitatively achieved and the organic spacer was recovered in
high yield. For n = 5, 6, and 8, increasing the length of the spacer resul
ts in a decreasing efficiency of this chemical treatment. Thermal oxidation
at 600-680 degrees C of the hybrid xerogels was also performed and elimina
tion of the organic spacer was obtained in all the cases. Mesoporous silica
with a narrow pore-size distribution was obtained by chemical treatment of
the xerogel with n = 2-4. Microporous silica was obtained by thermal treat
ment of the xerogel at 680 degrees C. All the materials were characterized
by SAXS, BET, and spectroscopy analysis.