Regensburg 2010 – scientific programme
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ST: Fachverband Strahlen- und Medizinphysik
ST 7: Nuclear Magnetic Resonance: Frontiers and Applications (CPP and ST)
ST 7.2: Talk
Tuesday, March 23, 2010, 14:00–14:15, H48
NMR studies of benzene mobility in microporous metal-organic framework MOF-5 — •Stefan Hertel1, Saeed Amirjalayer2, Markus Wehring1, Rochus Schmid2, and Frank Stallmach1 — 1Universität Leipzig, Fakultät für Physik und Geowissenschaften, Deutschland — 2Ruhr-Universität Bochum, Fakultät für Chemie und Biochemie, Deutschland
Microporous metal-organic frameworks (MOF) are crystalline coordination polymers with regular three dimensional pore networks. These pore networks enable adsorption and diffusion of guest molecules. Molecular Dynamics (MD) simulations show that benzene has a liquid-like mobility inside the pores of MOF-5. Nuclear Magnetic Resonance (NMR) methods allow experimental access to guest mobilities inside such pore networks. This report presents the results of pulsed field gradient NMR (PFG NMR) self-diffusion measurements of benzene adsorbed in MOF-5. In these experiments multi-exponential spin echo decays were observed, which are usually caused by different phases of self-diffusion. These different phases of benzene mobility were unexpected for diffusion of molecules inside an isotropic framework and have to originate in the host-guest and guest-guest interaction. By modern diffusion-relaxation correlation spectroscopy (DRCOSY) translational self-diffusion and microscopic relaxation behavior were correlated. Together with magic angle spinning (MAS) NMR spectroscopy these investigations reveal that the faster component of the diffusion coefficients can be assigned to diffusion inside the porous crystal structure of MOF-5.