ic5b01216_si_001.pdf (1.7 MB)
Efficiency of Polyoxometalate-Based Mesoporous Hybrids as Covalently Anchored Catalysts
journal contribution
posted on 2015-08-03, 00:00 authored by Faiza Bentaleb, Ourania Makrygenni, Dalil Brouri, Cristina Coelho Diogo, Ahmad Mehdi, Anna Proust, Franck Launay, Richard VillanneauPolyoxometalate
(POM) hybrids have been covalently immobilized through the formation
of amide bonds on several types of mesoporous silica. This work allows
the comparison of three POM-based mesoporous systems, obtained with
three different silica supports in which either the organic functions
of the support (amine vs carboxylic acid) and/or the structure of
the support itself (SBA-15 vs mesocellular foams (MCF)) were varied.
The resulting POM-based mesoporous systems have been studied in particular
by high resolution transmission electronic microscopy (HR-TEM) in
order to characterize the nanostructuration of the POMs inside the
pores/cells of the different materials. We thus have shown that the
best distribution and loading in POMs have been reached with SBA-15
functionalized with aminopropyl groups. In this case, the formation
of amide bonds in the materials has led to the nonaggregation of the
POMs inside the channels of the SBA-15. The catalytic activity of
the anchored systems has been evaluated through the epoxidation of
cyclooctene and cyclohexene with H2O2 in acetonitrile.
The reactivity of the different grafted POMs hybrids has been compared
to that in solution (homogeneous conditions). Parallels can be drawn
between the distribution of the POMs and the activity of the supported
systems. Furthermore, recycling tests together with catalyst filtration
experiments during the reaction allowed us to preclude the hypothesis
of a significant leaching of the supported catalyst.