NMR of Materials
NMR spectroscopic methods are used in our group to investigate materials such as metal-organic frameworks (MOFs), adsorption complexes (e.g., metal adsorption on biopolymers), as well as for in situ reaction monitoring in ionic liquids.
NMR on Metal-Organic Frameworks (Research Unit FOR 2433 MOF Switches)
Metal-Organic Frameworks (MOFs) represent a novel class of hybrid materials built from inorganic clusters and multifunctional organic linkers. The resulting two- or three dimensional network structures exhibit special characteristics such as high porosity, large specific surface area, and a high thermal stability. Numerous applications such as in gas purification, gas storage, catalysis, and separation processes are recently discussed.
In situ NMR Spectroscopy:
In situ NMR spectroscopy, e.g., of 129Xe, offers a variety of interesting parameters encoding information about the surface and pore system of porous materials. It is particularly suitable for the characterization of flexible frameworks to detect structural transformations such as the so-called gate-pressure-effect.
Depending on pressure and temperature, these flexible compounds show reversible structural changes during adsorption/desorption of several molecules (e.g. nitrogen, xenon).
Using a home-made high-pressure apparatus we are able to measure gas adsorption/desorption isotherms and isobars of MOFs. The apparatus allows for in situ regulation of Xenon pressure, i.e., inside the NMR magnet.
Bioinspired Materials
Diatoms are single-celled microorganisms capable of forming remarkable SiO2 (silica) based cell walls. Diatom biosilica exhibits hierarchical patterns of nano- to microscale features, which endow the material with interesting properties that are difficult to reproduce synthetically. The project combines methods for the deposition of inorganic materials under mild reaction conditions with genetic manipulation of diatom silica biogenesis to synthesize hierarchically structured organic-inorganic hybrid materials with interesting catalytic and optical properties. Diatom biosilica uniformly coated with enzymes and noble metal nanoparticles is studied with respect to the favorable catalytic properties of diatom biosilica. The catalytic tests are accompanied by extended analytical studies - especially of its surface properties - in order to interpret the catalytic behavior with respect to the hypothesized influence of the species-specific silica structures.