The combination of well-defined molecular cavities and chemical functionality makes crystalline porous solids attractive for a great number of technological applications, from catalysis to gas separation. However, in contrast to other widely applied synthetic solids such as polymers, the lack of processability of crystalline extended solids hampers their application. In this work, we demonstrate that metal–organic frameworks, a type of highly crystalline porous solid, can be made solution processable via outer surface functionalization using N-heterocyclic carbene ligands. Selective outer surface functionalization of relatively large nanoparticles (250 nm) of the well-known zeolitic imidazolate framework ZIF-67 allows for the stabilization of processable dispersions exhibiting permanent porosity. The resulting type III porous liquids can either be directly deployed as liquid adsorbents or be co-processed with state-of-the-art polymers to yield highly loaded mixed matrix membranes with excellent mechanical properties and an outstanding performance in the challenging separation of propylene from propane. We anticipate that this approach can be extended to other metal–organic frameworks and other applications.
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All data generated and/or analysed in this study are included in this published article and its supplementary information file and are also available from the corresponding author (Jorge Gascon) on reasonable request.
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L.S., A.K. and J.C. acknowledge support by the Deutsche Forschungsgemeinschaft in the priority program SPP 1928 COORNETs (Coordination Networks: Building Block for Functional Systems), grant no. CA 147/20-1 (J.C.). R.A., S.K and L.C. acknowledge the Supercomputing Laboratory at KAUST for computational resources (Cray XC40, ShaheenII). We thank P. M. Bhatt for helping with the propylene/propane adsorption kinetic study. King Abdullah University of Science and Technology is acknowledged for financial support.
The authors declare no competing interests.
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Knebel, A., Bavykina, A., Datta, S.J. et al. Solution processable metal–organic frameworks for mixed matrix membranes using porous liquids. Nat. Mater. 19, 1346–1353 (2020). https://doi.org/10.1038/s41563-020-0764-y