Diamino-functionalized SBA-15 as an efficient catalyst for the Knoevenagel reaction of benzaldehyde and malononitrile.

Abstract

Highly ordered mesoporous silica SBA-15 was synthesized and functionalized via silane chemistry with N-[3-(trimethoxysilyl)propyl]ethylenediamine to create surface base sites. The diamino-functionalized SBA-15 was characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), thermogravimetric analysis (TGA), Fourier transform infrared (FT-IR), elemental analysis (EA), and nitrogen physisorption measurements. The modified SBA-15 was used as an efficient heterogeneous base catalyst for the Knoevenagel condensation of benzaldehyde with malononitrile to produce benzylidene malononitrile as the principal product. Quantitative reaction conversion (>99%) was achieved under very mild conditions. It was also observed that no contribution from homogeneous catalysis of active amine species leaching into reaction solution was detected, indicating evidence for a real heterogeneous catalysis.