Synthesis of Periodic Large Mesoporous Organosilicas and Functionalization by Incorporation of Ligands into the Framework Wall

Highly ordered large mesopore organosilicas have been obtained by direct liquid crystal templating in acid media using bridged silsesquioxane (EtO) 3 Si−CH 2 −CH 2 −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. 29 Si 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.