Hybrid organic–inorganic catalytic porous materials synthesized at neutral pH in absence of structural directing agents

Abstract

Non-ordered porous hybrid materials with different distribution of pore sizes have been synthesized from organic–inorganic bridged silsesquioxane precursors using an NH₄F catalyzed sol–gel route. This methodology has allowed to obtain high surface area porous materials in absence of structural directing agents or surfactant molecules. A variety of organic linkers, such as benzene, disulfide, diamine, ethane and ethylene groups, were incorporated within the framework, and the effective integration was confirmed by elemental and thermogravimetrical analyses, Raman and NMR spectroscopies. The pore dimensions of the hybrids could be modified, within the mesoporous range, with the NH₄F synthesis and the characteristics of the organic linker. Basic catalytic active sites have been introduced in the organic linkers of the hybrid porous materials that are active and selective for Knoevenagel condensations, showing the possibility to heterogenize organic catalysts while preserving their activity and selectivity by means of these porous organic–inorganic hybrids.