X-Nuclei NMR Self-Diffusion Studies in Mesoporous Silica Foam and Microporous MOF CuBTC |
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| Authors: | Stefan Schlayer Anne-Kristin Pusch Friederike Pielenz Steffen Beckert Mikulá? Peksa Carsten Horch Lutz Moschkowitz Wolf-Dietrich Einicke Frank Stallmach |
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| Affiliation: | 1.Institute of Experimental Physics I, Universität Leipzig, Linnéstr. 5, Leipzig 04103, Germany; E-Mails: (S.S.); (A.-K.P.); (F.P.); (S.B.); (M.P.); (C.H.); (L.M.);2.Institute of Technical Chemistry, Universität Leipzig, Linnéstr. 4, Leipzig 04103, Germany; E-Mail: |
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| Abstract: | A standard X-observe NMR probe was equipped with a z-gradient coil to enable high-sensitivity pulsed field gradient NMR diffusion studies of Li+ and Cs+ cations of aqueous salt solutions in a high-porosity mesocellular silica foam (MCF) and of CO2 adsorbed in metal-organic frameworks (MOF). The coil design and the necessary probe modifications, which yield pulsed field gradients of up to ±16.2 Tm-1, are introduced. The system was calibrated at 2H resonance frequency and successfully applied for diffusion studies at 7Li, 23Na, 13C and 133Cs frequencies. Significant reductions of the diffusivities of the cations in LiClac and CsClac solution introduced into MCFs are observed. By comparison of the diffusion behavior with the bulk solutions, a tortuosity of the silica foam of 4.5 ± 0.6 was derived. Single component self-diffusion of CO2 and CH4 (measured by 1H NMR) as well as self-diffusion of the individual components in CO2/CH4 mixtures was studied in the MOF CuBTC. The experimental results confirm high mobilities of the adsorbed gases and trends for diffusion separation factors predicted by MD simulations. |
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| Keywords: | probe design diffusion 7Li 13C 133Cs PFG NMR CuBTC MCF |
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