Organically modified hexagonal mesoporous silicas (HMS)- remarkable effect of preparation solvent on physical and chemical properties

The preparation of a series of aminopropyl-substituted micelle templated silicas is presented, in which the materials are synthesised by a one-step co-condensation route using dodecylamine as template. The effect of solvent composition on the material properties, reactivity and catalytic activity is discussed. Increasing the water content of the preparation solvent causes an increase in the framework pore diameter, and, at high water contents, a great deal of textural porosity is seen. Particle size does not change over the range studied, in contrast to other micelle templated silica systems published recently. However, two materials, prepared at intermediate solvent compositions have very different morphology, and curiously, very different reactivities as nucleophiles. Their catalytic activity in the Knoevenagel reaction does however follow the same trend as for all the other samples. The processes occurring are discussed.