In situ direct bifunctionalization of mesoporous silica SBA-15

Abstract

A novel bifunctional mesoporous material MA/SBA-15 has been synthesized in one pot by in situ introduction of aluminium and magnesium salts and controlling the synthesis conditions, with the framework insertion of aluminium and high dispersion of magnesia resulting in both the strong basic and acidic sites being simultaneously formed on SBA-15. Characterization by low angle X-ray diffraction, N₂ adsorption, high-resolution transmission electron microscopes (HRTEM), ¹H and ²⁷Al magic-angle spinning (MAS) NMR has been carried out to evaluate the effect of the heteroatoms. The acidic–basic properties of bifunctional MA/SBA-15 have been assessed by NH₃ and CO₂-TPD experiments, the Hammett indicator method and titration. The results of ¹H and ²⁷Al magic-angle spinning (MAS) NMR indicate that the location of most aluminium is in a tetrahedral coordination which results in a large amount of Brønsted acid sites. This novel material possesses high activity for the degradation of N-nitrosopyrrolidine (NPYR), a typical volatile nitrosamine, which is attributed to the strong Brønsted acid sites.