Synthesis, characterization and catalytic activity of acid–base bifunctional materials by controlling steric hindrance

Two acid–base bifunctional mesoporous materials Benzyl-APS-S-SBA-15 and Anthracyl-APS-S-SBA-15 (APS: (3-trimethoxysilanyl-propyl)-amine) were successfully synthesized by a direct synthesis method. The influence of steric hindrance upon prevention of interaction between acid and base was investigated by using two different secondary amines, benzyl-(3-trimethoxysilanyl-propyl)-amine and anthracyl methyl-(3-trimethoxysilanyl-propyl)-amine. X-ray diffraction (XRD), N2 adsorption, thermogravimetric analysis (TGA), scanning electron micrographs (SEM), transmission electron micrographs (TEM), elemental analysis, back titration, and 29Si magic-anglespinning (MAS) NMR were employed to characterize the synthesized mesoporous bifunctional materials. The experimental results indicate that the guests can be well dispersed in the channel of SBA-15, and the obtained materials exhibit excellent acid–basic properties, which make it possess high activity for the aldol condensation of acetone with 4-nitrobenzaldehyde.