Periodic mesoporous organosilicas: versatile materials hosting catalytic centers
26 January 2018
Campus Drie Eiken, Promotiezaal Q0.02 - Universiteitsplein 1 - 2610 Antwerpen-Wilrijk (route: UAntwerpen, Campus Drie Eiken
Organization / co-organization:
Department of Chemistry
PhD defence Ward Huybrechts - Faculty of Science, Department of Chemistry
Periodic mesoporous organosilicas have been standing in the center of attention of many scientists working on hybrid materials since they first appeared in 1999. Due to their both inorganic and organic nature, they offer the best of both worlds.
PMOs have found their way to a variety of applications, often in comparison to their siliceous analogues. Certain applications however, require the presence of very specific functional groups that are not always directly attainable by utilizing a certain precursor. Furthermore, modifying the precursors with the desired functionality before PMO synthesis can lead to bulky building blocks that no longer offer the desired ordering or pore characteristics in the final material. It is therefore crucial that research is performed on post-synthetical modification reactions.
Nevertheless, transferring known organic modification reactions to the world of PMOs is hardly straightforward. Besides the reactions having to occur in a confined space, the substrate molecule is built in to the solid framework as well. Hence, the substrate molecule cannot arrange itself towards the reagents, nor can the anchoring carbon-silicon bonds be cleaved because of the reaction conditions.
In this work, we explored the potential of PMOs by performing post-synthetical modification reactions. First of all bromination of aniline bridged PMOs was obtained by performing a one-pot diazotation-de-diazotation-bromination reaction. This shows the opportunities towards functionalization of these materials in a variety of different fields.
Furthermore, the development of L-serine modified benzene bridged PMO was investigated. This material was then catalytically tested in the aldol condensation of acetone and 4-nitrobenzaldehyde. This test reaction shows the potential of PMOs towards valorization of biomass-based resources into biodiesel. Moreover, compared to its siliceous counterpart, PMOs can offer significant advantages.
Finally, the synthesis of a guanylated PMO was explored as a means to create a PMO for base catalysis. Although the modification and subsequent characterization of this PMO was not straightforward, the first preliminary catalytic tests were very promising.