Highly ordered large mesopore organosilicas have been obtained by direct liquid crystal
templating in acid media using bridged silsesquioxane (EtO)3Si−CH2−CH2−Si(OEt)3 [bis(triethoxysilyl)ethane, BTSE] precursor and triblock copolymers as structure-directing
species. The degree of long-range ordering of the structure as determined from X-ray
diffraction and transmission electron microscopy, and the most probable pore diameter, in
the range 4−8 nm, were observed to depend on the concentration of triblock copolymer used
in the synthesis. Further pore-wall functionalization was achieved by co-condensation with
Cu(II)-complexed N,N‘-bis[3-(trimethoxysilyl)propyl]ethylenediamine (BTSPED). Surfactant
extraction produces periodic mesoporous organosilicas functionalized with this complex in
the framework, from which the Cu(II) can then be removed by acid leaching. Such hybrid
bridged bifunctional organosilicas are homogeneously mesoporous, and the pore diameter
increases in the range 11−21 nm as the mole ratio of BTSPED to BTSE is increased from
0.1 to 0.3. 29Si MAS NMR shows that under the conditions used, no cleavage of the Si−C
bond occurs, and suggests that the degree of condensation is higher in the bridged bifunctional
organosilicas than in the bridged monofunctional organosilicas.
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