Some considerations regarding the mesopore structure and order in MSU-3 and MSU-F (organo)silicas

Abstract

Development of mesoporous materials and specifically mesoporous silica was an advancement of that of microporous materials such as zeolites. Major advantages associated with mesopore nanostructures have largely depended on bigger pore size, high pore order and rather high flexibility in modification of the pore system. For this reason, large-pore and highly ordered mesoporous silica (e.g. SBA-15) were introduced taking advantage of co-polymer surfactants as structure directing agents, while pore size expansion was still extended toward making mesoporous silica foams. At the same time neutral cooperative self-assembly of silica precursors and non-ionic surfactants resulted in facile preparation of MSU-X family of mesoporous silica obtained in milder synthesis conditions. This research tries to bring new insights into the versatility of MSU-X preparations that would show highly ordered or engineered mesopore network. The mesostructural properties of MSU-3 and MSU-F materials subjected to hydrothermal processing and different functionalization were studied in detail with gas adsorption, TEM and XRD analyses. Use of different silica precursors and functionalizations brought differences in the mesopore structure. It was possible, in these syntheses, to obtain highly hexagonal mesopore order in the hybrid MSU-3 in a co-condensation synthesis with MPTMS in presence of inorganic silica precursor. On the other hand, during the course of silica foam (MSU-F) preparations, due to the effect of post-synthesis hydrothermal processing, considerable modification of the large mesopores brought the opportunity to achieve fully bimodal (both channel-like and mesocellular) pore morphologies in the material framework.