Gas separations is a process relevant to a variety of chemical industries ranging from petrochemicals and biofuels to pharmaceuticals. The importance of this process has inspired the development of novel materials and technology tailored for efficient membrane-based technologies. The main long-term goal of the work presented in this dissertation is to develop the fundamental science for a conceptually new type of gas separations which is based on induction of single-file diffusion (SFD) for a selected component of a gas mixture inside a microporous membrane. SFD can be exhibited by molecules confined in narrow unidimensional channels that prevent mutual molecular passages. The unique properties associated with this anomalous diffusion mechanism offer the possibility of highly-selective separations.

In this work a diffusion NMR technique at high magnetic field and high magnetic field gradient has enabled the first experimental observation of SFD of molecular mixtures and provided insight into the relationship between SFD rates of pure-sorbates and their respective mixtures. The studied gases include methane and carbon dioxide, which are relevant for natural gas separations. Molecular clustering in the investigated model single-file channels is proposed to explain the observed relationship between the mixture and one-component mobilities and to reconcile reported experimental data with predictions of a random walk model.

In addition to carbon dioxide, hydrogen sulfide represents another hazardous impurity in natural gas. Zeolitic imidazolate frameworks (ZIFs) are promising candidates for natural gas separation and processing. Diffusion NMR was applied to study dynamics of hydrogen sulfide in ZIF-8. Preliminary results reveal an extremely low mobility of hydrogen sulfide in this material. Investigation of the influence of hydrogen sulfide exposure on the transport properties of ZIF-8 is currently underway.

NMR diffusometry is a powerful technique for studying diffusion phenomena in porous materials. However, short NMR transverse relaxation times under conditions of extreme confinement in microporous materials limit applicability of standard diffusion NMR. In an effort to overcome this challenge, a NMR probe capable of performing diffusion measurements under magic angle spinning (MAS) was calibrated and applied for diffusion studies in ZIFs. These studies demonstrate that MAS can drastically improve conditions of NMR diffusion measurements.