The Polymeric Upper Bound for N2/NF3 Separation and Beyond; ZIF-8 Containing Mixed Matrix Membranes

Global production for NF₃ is continuously increasing, especially due to its heavy consumption in the semiconductor industry. Even though the amount of its emission is relatively small compared to other greenhouse gases, especially CO₂, its relatively long atmospheric lifetime makes its emissions cumulative, possibly causing global climate change. Membrane-based separation technique can be an attractive alternative for the energy-efficient NF₃ recovery, and thereby, evaluating the N₂/NF₃ separation performance by using commercial polymeric membranes is crucial. For the first time, the empirical N₂/NF₃ upper bound relationship was established by using a wide variety of commercial polymeric membranes including both glassy and rubbery polymers based on their single gas (i.e., N₂ and NF₃) permeation characterization. Among them, 6FDA-DAM:DABA (3:2), Teflon® AF 2400 and PTMSP were found to show relatively high N₂/NF₃ separation performance. The theoretical N₂/NF₃ upper bound curve was also defined and it was comparable with our empirical upper bound limit. In addition, diverse zeolitic imidazolate frameworks (i.e., commercial ZIF-8 (Basolite® Z1200), house-made ZIF-8 or ICA-ZIF-8) were incorporated into Matrimid® 5218 as molecular sieves to improve the N₂/NF₃ separation performance. More specifically, the effect of solvent, particle size and ligands on the transport properties in mixed matrix membranes was investigated.