X-Nuclei NMR Self-Diffusion Studies in Mesoporous Silica Foam and Microporous MOF CuBTC

A standard X-observe NMR probe was equipped with a z-gradient coil to enable high-sensitivity pulsed field gradient NMR diffusion studies of [Formula: see text] and [Formula: see text] cations of aqueous salt solutions in a high-porosity mesocellular silica foam (MCF) and of [Formula: see text] adsorbed in metal-organic frameworks (MOF). The coil design and the necessary probe modifications, which yield pulsed field gradients of up to [Formula: see text] , are introduced. The system was calibrated at [Formula: see text] resonance frequency and successfully applied for diffusion studies at [Formula: see text] , [Formula: see text] , [Formula: see text] and [Formula: see text] frequencies. Significant reductions of the diffusivities of the cations in [Formula: see text] and [Formula: see text] solution introduced into MCFs are observed. By comparison of the diffusion behavior with the bulk solutions, a tortuosity of the silica foam of [Formula: see text] was derived. Single component self-diffusion of [Formula: see text] and [Formula: see text] (measured by [Formula: see text] NMR) as well as self-diffusion of the individual components in [Formula: see text] / [Formula: see text] 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.