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 ma gnetic resonance (NMR) spectroscopy to the structural characterization of microporous host-guest systems is demonstrated by a series of soda lites 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-2 9 and Al-27 NMR provide information on the local structure and composi tion of the framework, Na-23 and H-1 NMR give insights into the struct ure and dynamics of the cage fillings. The number of crystallographica lly inequivalent Si, Al and Na sites in the sodalite structures is det ermined from the Si-29, Al-27 and Na-23 NMR spectra and their local ge ometry is characterized by detailed interpretation of the isotropic ch emical shifts and the Al-27 and Na-23 quadrupole parameters. Dynamic r eorientation processes of the guest species and structural phase trans itions of distinct sodalite compositions were studied by multinuclear magic angle spinning (MAS) NMR at variable temperature. Besides MAS NM R, double rotation (DOR) NMR experiments at different field strengths were performed for Al-27 and Na-23 to resolve strongly overlapping lin es of the MAS NMR spectra.