Integrated in situ spectroscopic characterization of bi-functional nanoporous hybrid catalysts

Abstract

Bi-functional catalysts possess various catalytic sites and can catalyze different types of reactions in a single-pot cascade manner. Herein, we report the synthesis and characterization of mono- and bifunctional silica-based mesoporous hybrid catalysts involving acid and base active sites. The ability for cooperative catalysis has been investigated using a multi-technique approach involving powder X-ray diffraction, FT-IR, and multinuclear MAS NMR spectroscopy, as well as thermogravimetric analysis. To elucidate the nature and strength of multifunctional catalytic sites, different types of probe molecules were employed and studied using spectroscopic techniques. The results show that the activity of the mesoporous surface-grafted acid and/or base sites is directly related to the intimacy criterion, the separation between the different types of catalytic sites. The presence or absence of mutual interactions between the different catalytic sites dictates the selectivity and yield of the reactions.

Keywords

• MAS NMR
• FTIR
• Bi-functional nanoporous hybrids
• Amine groups
• Sulphonic groups
• Green grafting