MULTINUCLEAR SOLID-STATE NMR OF HOST-GUEST SYSTEMS WITH TO2 (T=SI, AL) HOST-FRAMEWORKS - A CASE-STUDY ON SODALITES

The application of high-resolution multinuclear solid state nuclear magnetic resonance (NMR) spectroscopy to the structural characterization of microporous host-guest systems is demonstrated by a series of sodalites with aluminosilicate, aluminate and silicate host-frameworks and a large variety of guest species (inorganic anions and cations, H2O, OH-, organic molecules) enclathrated in the sodalite cages. While Si-29 and Al-27 NMR provide information on the local structure and composition of the framework, Na-23 and H-1 NMR give insights into the structure and dynamics of the cage fillings. The number of crystallographically inequivalent Si, Al and Na sites in the sodalite structures is determined from the Si-29, Al-27 and Na-23 NMR spectra and their local geometry is characterized by detailed interpretation of the isotropic chemical shifts and the Al-27 and Na-23 quadrupole parameters. Dynamic reorientation processes of the guest species and structural phase transitions of distinct sodalite compositions were studied by multinuclear magic angle spinning (MAS) NMR at variable temperature. Besides MAS NMR, double rotation (DOR) NMR experiments at different field strengths were performed for Al-27 and Na-23 to resolve strongly overlapping lines of the MAS NMR spectra.