The objective of this project is to develop structure-property relationships that will enable the fabrication of microporous membranes for N2/CO2 separation with high selectivity, which are achieved by selective induction of single-file diffusion to N2 molecules. The research effort is split between the following tasks: (1) fabrication of membrane supports with nanopore diameters below 5 nm and (2) characterization of the diffusion properties of gas mixtures in these membranes. Application of a unique diffusion NMR technique enables distinguishing between different diffusion mechanisms for different gas components inside the membrane on the microscopic length scales. Successful completion of the proposed research affords a transformative membrane-based technology to separate CO2 from combustion gas mixtures. The research plan is integrated with a recruitment program and supervised research for undergraduate students, especially students from the underrepresented groups, as well as mentoring and outreach. The students will be trained to use a unique diffusion NMR technique at the National High Magnetic Field Laboratory.