Snβ zeolites are amongst the most effective heterogeneous catalysts for the Baeyer–Villiger (BV) oxidation of ketones with aqueous hydrogen peroxide (H2O2). The high selectivity is rooted in the activation of the carbonyl substrate through interaction with the isolated SnIV sites. However, these sites are also accessible to other molecules in the reaction mixture (in particular the co-solvent and product). In this contribution, we report the impact of competitive adsorption on the Snβ-catalyzed BV oxidation of cyclohexanone with aqueous H2O2. We furthermore prepared a series of Snβ zeolites with varying amounts of framework silanols and quantified their hydrophilicities with water adsorption and IR experiments. By correlating the results with catalytic data, we show that Snβ zeolites with an intermediate hydrophilicity achieve the highest activity. Our adaptable post-synthetic synthesis allows us to tune the material synthesis, resulting in enhanced activity compared with conventional hydrothermal Snβ.
Bibliographical noteFunding Information:
The authors acknowledge financial support from UW–Madison. S.C. thanks ETH Zurich for financial support (ETH-38 12-1), P.W. acknowledges the SNF (200021_146661) for funding and P.M. thanks the U.S. Army Research Office for financial support under grant W911NF-15-1-0134.
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- Baeyer–Villiger oxidation
- Snβ zeolites
- mass transfer