Combined In-Situ/Operando Spectroscopy Reactor Facility
Zusammenfassung der Projektergebnisse
Ionic liquids are molten salts with melting points below 100°C. Their physico-chemical properties can be tuned by selecting cation-anion combinations from the huge library available. Their unusual properties, such as an extremely low vapor pressure, have stimulated the development of new concepts emerging at the border between homogeneous and heterogeneous catalysis. Among them is the so-called ”Supported Ionic Liquid Phase” (SILP) catalysis, where a thin IL layer immobilizes homogeneously dissolved transition metal complexes on a high-surface-area support. A special type of SILP catalysts involves ionic liquid crystals (ILCs). The existence of an ordered phase in the liquid-crystalline state leads to temperature-switchable environment and, possibly, to temperature-switchable selectivity. In order to study the influence of the support on the phase transitions of ILC-SILP materials. We have studied various ILC-SILP systems and were able to follow the phase transitions on powders. 1. The influence of the pore sizes and of the filling of the support was studied by Diffuse Reflectance IR Fourier Transform Spectroscopy (DRIFTS). Here, Si-based powders with pore sizes ranging from 10 to 50 nm were filled with the ILCs 1-methyl-3-octadecylimidazolium trifluorosulfate [C18C1IM][OTf] and 1- methyl-3-hexadecylimidazolium trifluorosulfate [C16C1Im][OTf]. The smallest fillings have revealed the existence of a contact layer of one or two monolayers in thickness, which shows a single phase transition. Beyond that contact layer, the ILCs show both solid-to-smectic and smectic-to-liquid phase transitions at temperatures close to that of the bulk. 2. Complete ILC-SILP systems have been studied. Quantities of [NiCl2(C12MIM)2] and [NiCl2(C12C12IM)2] catalysts solubilized in the IL 1,3-didodecylimidazolium tetrafluoroborate [C12C12IM][BF4] ranging from 1 to 10 wt.% were investigated under confinement on silica-100. These experiments have shown that the presence of the catalyst does not disturb the smectic-to-liquid transition temperature. These experiments involved the identifications of extremely small shifts of absorption bands in DRIFTS in a practical time scale. Moreover, the experiments were performed and repeated using a fully computercontrolled protocol so that it was possible to investigate the reproducibility and decrease the error on the measurements. Such measurements under these particular conditions are only possible on our apparatus.
Projektbezogene Publikationen (Auswahl)
- Surface-Functionalized Ionic Liquid Crystal–Supported Ionic Liquid Phase Materials: Ionic Liquid Crystals in Mesopores. ChemPhysChem 12 (2011) pp. 3539–3546
Florian T. U. Kohler, Bruno Morain, Alexander Weiß, Mathias Laurin, Jörg Libuda, Valentin Wagner, Berthold U. Melcher, Xinjiao Wang, Karsten Meyer, and Peter Wasserscheid
- Functional nickel complexes of N- heterocyclic carbene ligands in pre-organized and supported thin film materials. Journal of Materials Chemistry 22 (2012) pp. 1893-1898
Xinjiao Wang, Marek Sobota, Florian T. U. Kohler, Bruno Morain, Berthold U. Melcher, Mathias Laurin, Peter Wasserscheid, Jörg Libuda, and Karsten Meyer
