Daniel HEMMETER1, Daniel KREMITZL2, Peter SCHULZ2, Peter WASSERSCHEID2, Florian MAIER1, Hans-Peter STEINRÜCK1
1Chair of Physical Chemistry II, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
2Chair of Chemical Engineering I, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
Due to their extremely low volatility, high thermal stability and enormous structural variability, ionic liquids (ILs) are attractive solvents for catalytic transformations. One outstanding application field is supported ionic liquid phase (SILP) catalysis where a solid, porous support is impregnated with a thin film of a catalyst dissolved in an IL. The very high surface area of the resulting catalyst material makes a rational design of the gas/IL interface a substantial optimization parameter for the catalytic process – a concept referred to as called interface-enhanced SILP. In this work, we deliberately modified the composition of the gas/IL interface with a very pronounced enrichment of an organometallic Pt(II) catalyst at the surface. For this, we introduced highly surface-affine groups into the ligand system of the complex acting like buoys to trigger surface accumulation. We found that the enrichment is most effective at lowest nominal concentration of the catalyst in solution, which is particularly promising for catalytic applications. For these investigations, angle-resolved X-ray photoelectron spectroscopy (ARXPS) has proven to be a powerful tool. Our ARXPS setup allows for the simultaneous acquisition of XP spectra in normal and grazing emission, representing the composition of the bulk and the topmost molecular layer of the sample, respectively.