Abstract:
Usually, the term porosity refers to solid materials, such as carbons, zeolites, metal-organic frameworks, etc. However, processing of these solid powders is challenging. More often than not, for real-world applications, porous materials are required to be processed in a shape of, for instance, membrane or monolith. In our recent research1, 2 we explore the possibilities on how to process solid Zeolitic Imidazolate Frameworks (ZIFs) through a liquid phase mediation. Specifically, we modify the surface of ZIFs with carbene 1,3-bis(2,6-diisopropylphenyl)-1H-imidazol-3-ium-2-ide in mesitylene in order to get a type III porous liquid (PL). We explored how different parameters such as particle size, topology, metal and linker nature affect stability of ZIF-based PL. It was found that ZIF particle size and its topology have the highest impact here.
Further, we employed several PLs to obtain mixed matrix membranes. We showed that modification of ZIFs with the carbene promotes the interaction between ZIF particles and polymers, yielding in highly loaded MMMs1. For comparison, we also fabricated similar membranes, but without carbene modification. Comparing those membranes we found that modification with the carbene prevents swelling and/or dilatation of the MOF-polymer interface. Thus, MMMs with modified ZIFs in general show better permeability and selectivity in both tests: single gas and mixed gas separation. For instance, in mixed gas separation in the case of ZIF-67 based membranes, we observe 89% permeability and 82% selectivity enchantment for propane/propylene separation for similar loadings.
1. Knebel, A.; Bavykina, A.; Datta, S. J.; Sundermann, L.; Garzon-Tovar, L.; Lebedev, Y.; Durini, S.; Ahmad, R.; Kozlov, S. M.; Shterk, G.; Karunakaran, M.; Carja, I. D.; Simic, D.; Weilert, I.; Klüppel, M.; Giese, U.; Cavallo, L.; Rueping, M.; Eddaoudi, M.; Caro, J.; Gascon, J., Solution processable metal–organic frameworks for mixed matrix membranes using porous liquids. Nature Materials 2020, 19 (12), 1346-1353.
2. Poloneeva, D.; Datta, S. J.; Garzon-Tovar, L.; Durini, S.; Rueping, M.; Eddaoudi, M.; Bavykina, A.; Gascon, J., Toward Liquid Phase Processable Metal Organic Frameworks: Dream or Reality? Accounts of Materials Research 2021, 2 (12), 1133-1140.