Porous materials are widely used in industry for applications that include chemical separations and gas scrubbing. These materials are typically porous solids, although the liquid state can be easier to manipulate in industrial settings. The idea of combining the size and shape selectivity of porous domains with the fluidity of liquids is a promising one and porous liquids composed of functionalized organic cages have recently attracted attention. Here we describe an ionic-liquid, porous, tetrahedral coordination cage. Complementing the gas binding observed in other porous liquids, this material also encapsulates non-gaseous guests—shape and size selectivity was observed for a series of isomeric alcohols. Three gaseous chlorofluorocarbon guests, trichlorofluoromethane, dichlorodifluoromethane and chlorotrifluoromethane, were also shown to be taken up by the liquid coordination cage with an affinity that increased with their size. We hope that these findings will lead to the synthesis of other porous liquids whose guest-uptake properties may be tailored to fulfil specific functions.
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The authors declare that all data supporting the findings of this study are included within the article and its Supplementary Information, and are also available from the authors upon request.
O’Reilly, N., Giri, N. & James, S. L. Porous liquids. Chem. Eur. J. 13, 3020–3025 (2007).
Zhang, J. et al. Porous liquids: a promising class of media for gas separation. Angew. Chem. Int. Ed. 54, 932–936 (2015).
Li, P. et al. Electrostatic-assisted liquefaction of porous carbons. Angew. Chem. Int. Ed. 56, 14958–14962 (2017).
Costa Gomes, M., Pison, L., Červinka, C. & Padua, A. Porous ionic liquids or liquid metal–organic frameworks? Angew. Chem. Int. Ed. 57, 11909–11912 (2018).
Giri, N. et al. Liquids with permanent porosity. Nature 527, 216–220 (2015).
Shan, W. et al. New class of type III porous liquids: a promising platform for rational adjustment of gas sorption behavior. ACS Appl. Mater. Inter. 10, 32–36 (2018).
Liu, H. et al. A hybrid absorption–adsorption method to efficiently capture carbon. Nat. Commun. 5, 5147 (2014).
Gaillac, R. et al. Liquid metal–organic frameworks. Nat. Mater. 16, 1149–1155 (2017).
Bennett, T. D. & Horike, S. Liquid, glass and amorphous solid states of coordination polymers and metal–organic frameworks. Nat. Rev. Mater. 3, 431–440 (2018).
Jie, K. et al. Transforming porous organic cages into porous ionic liquids via a supramolecular complexation strategy. Angew. Chem. Int. Ed. https://doi.org/10.1002/anie.201912068 (2020).
Greenaway, R. L. et al. Understanding gas capacity, guest selectivity, and diffusion in porous liquids. Chem. Sci. 8, 2640–2651 (2017).
Zhang, F. et al. Thermodynamics and kinetics of gas storage in porous liquids. J. Phys. Chem. B 120, 7195–7200 (2016).
Greenhouse Gas Protocol: A Corporate Accounting and Reporting Standard (WBCSD and WRI, 2012).
Castilla, A. M., Ronson, T. K. & Nitschke, J. R. Sequence-dependent guest release triggered by orthogonal chemical signals. J. Am. Chem. Soc. 138, 2342–2351 (2016).
Tao, S. J. Positronium annihilation in molecular substances. J. Chem. Phys. 56, 5499–5510 (1972).
Kleywegt, G. J. & Alwyn Jones, T. Detection, delineation, measurement and display of cavities in macromolecular structures. Acta Crystallogr. D 50, 178–185 (1994).
Montzka, S. A. et al. An unexpected and persistent increase in global emissions of ozone-depleting CFC-11. Nature 557, 413–417 (2018).
Rigby, M. et al. Increase in CFC-11 emissions from eastern China based on atmospheric observations. Nature 569, 546–550 (2019).
Chen, T. H. et al. Mesoporous fluorinated metal–organic frameworks with exceptional adsorption of fluorocarbons and CFCs. Angew. Chem. Int. Ed. 54, 13902–13906 (2015).
Shiflett, M. B. & Yokozeki, A. Hydrogen substitution effect on the solubility of perhalogenated compounds in ionic liquid [bmim][PF6]. Fluid Phase Equilib. 259, 210–217 (2007).
Yang, D. et al. Encapsulation of halocarbons in a tetrahedral anion cage. Angew. Chem. Int. Ed. 54, 8658–8661 (2015).
Heinz, T., Rudkevich, D. M. & Rebek, J. Pairwise selection of guests in a cylindrical molecular capsule of nanometre dimensions. Nature 394, 764–766 (1998).
Akine, S., Miyashita, M. & Nabeshima, T. A metallo-molecular cage that can close the apertures with coordination bonds. J. Am. Chem. Soc. 139, 4631–4634 (2017).
Käseborn, M., Holstein, J. J., Clever, G. H. & Lützen, A. A rotaxane-like cage-in-ring structural motif for a metallosupramolecular Pd6L12 aggregate. Angew. Chem. Int. Ed. 57, 12171–12175 (2018).
Hof, F., Nuckolls, C. & Rebek, J. Diversity and selection in self-assembled tetrameric capsules. J. Am. Chem. Soc. 122, 4251–4252 (2000).
Yan, Y. et al. Smart self-assemblies based on a surfactant-encapsulated photoresponsive polyoxometalate complex. Angew. Chem. Int. Ed. 49, 9233–9236 (2010).
Wang, M., Zheng, Y.-R., Ghosh, K. & Stang, P. J. Metallosupramolecular tetragonal prisms via multicomponent coordination-driven template free self-assembly. J. Am. Chem. Soc. 132, 1–9 (2010).
Mondal, B. & Mukherjee, P. S. Cage encapsulated gold nanoparticles as heterogeneous photocatalyst for facile and selective reduction of nitroarenes to azo compounds. J. Am. Chem. Soc. 140, 12592–12601 (2018).
Bondy, C. R., Gale, P. A. & Loeb, S. J. Metal–organic anion receptors: arranging urea hydrogen-bond donors to encapsulate sulfate ions. J. Am. Chem. Soc. 126, 5030–5031 (2004).
Scherer, M., Caulder, D. L., Johnson, D. W. & Raymond, K. N. Triple helicate–tetrahedral cluster interconversion controlled by host–guest interactions. Angew. Chem. Int. Ed. 38, 1588–1592 (1999).
Liu, Y., Hu, C., Comotti, A. & Ward, M. D. Supramolecular Archimedean cages assembled with 72 hydrogen bonds. Science 333, 436–440 (2011).
Ajami, D. & Rebek, J. Compressed alkanes in reversible encapsulation complexes. Nat. Chem. 1, 87–90 (2009).
Roy, X. et al. Prussian blue nanocontainers: selectively permeable hollow metal–organic capsules from block ionomer emulsion-induced assembly. J. Am. Chem. Soc. 133, 8420–8423 (2011).
Campos-Fernández, C. S. et al. Anion template effect on the self-assembly and interconversion of metallacyclophanes. J. Am. Chem. Soc. 127, 12909–12923 (2005).
Turunen, L., Warzok, U., Schalley, C. A. & Rissanen, K. Nano-sized I12L6 molecular capsules based on the [N⋅⋅⋅I+⋅⋅⋅N] halogen bond. Chem 3, 861–869 (2017).
Sun, L. Y. et al. Template synthesis of three-dimensional hexakisimidazolium cages. Angew. Chem. Int. Ed. 57, 5161–5165 (2018).
Markiewicz, G. et al. Selective C70 encapsulation by a robust octameric nanospheroid held together by 48 cooperative hydrogen bonds. Nat. Commun. 8, 15109 (2017).
Jie, K. et al. Linear positional isomer sorting in nonporous adaptive crystals of a pillararene. J. Am. Chem. Soc. 140, 3190–3193 (2018).
Jia, C. et al. Selective binding of choline by a phosphate-coordination-based triple helicate featuring an aromatic box. Nat. Commun. 8, 938 (2017).
Brachvogel, R. C., Hampel, F. & Von Delius, M. Self-assembly of dynamic orthoester cryptates. Nat. Commun. 6, 7129 (2015).
Ozores, H. L., Amorín, M. & Granja, J. R. Self-assembling molecular capsules based on α,γ-cyclic peptides. J. Am. Chem. Soc. 139, 776–784 (2017).
Xuan, W. et al. A chiral quadruple-stranded helicate cage for enantioselective recognition and separation. J. Am. Chem. Soc. 134, 6904–6907 (2012).
Preston, D., Sutton, J. J., Gordon, K. C. & Crowley, J. D. A nona-nuclear heterometallic Pd3Pt6 ‘donut’-shaped cage: molecular recognition and photocatalysis. Angew. Chem. Int. Ed. 57, 8659–8663 (2018).
Chepelin, O. et al. Luminescent, enantiopure, phenylatopyridine iridium-based coordination capsules. J. Am. Chem. Soc. 134, 19334–19337 (2012).
Krieg, E. et al. A recyclable supramolecular membrane for size-selective separation of nanoparticles. Nat. Nanotechnol. 6, 141–146 (2011).
Lee, D. W. et al. Supramolecular fishing for plasma membrane proteins using an ultrastable synthetic host–guest binding pair. Nat. Chem. 3, 154–159 (2011).
Yoshizawa, M., Tamura, M. & Fujita, M. Diels–Alder in aqueous molecular hosts: unusual regioselectivity and efficient catalysis. Science 312, 251–254 (2006).
Cullen, W. et al. Highly efficient catalysis of the Kemp elimination in the cavity of a cubic coordination cage. Nat. Chem. 8, 231–236 (2016).
Zhang, Q., Catti, L., Pleiss, J. & Tiefenbacher, K. Terpene cyclizations inside a supramolecular catalyst: leaving-group-controlled product selectivity and mechanistic studies. J. Am. Chem. Soc. 139, 11482–11492 (2017).
Fukui, T. Control over differentiation of a metastable supramolecular assembly in one and two dimensions. Nat. Chem. 9, 493–499 (2017).
L.M., A.B.G., C.J.E.H. and A.T. acknowledge support from the UK Engineering and Physical Sciences Research Council (EPSRC EP/P027067/1) and the European Research Council (ERC 695009). C.C.P. acknowledges the Engineering and Physical Sciences Research Council for funding (EPSRC DTP grant EP/M508007/1). L.L. acknowledges an EPSRC Departmental Studentship. A.W. and A.R.S. acknowledge the National Centre for Research and Development (LIDER/024/391/L-5/13/NCBR/2014) and National Science Centre in Poland (PRELUDIUM UMO-2016/21/N/ST5/00851) for funding). T.D.B. thanks the Royal Society for a University Research Fellowship (UF150021), and for a Research Grant (RSG\R1\180395). C.M.D. acknowledges the Veski Inspiring Women Fellowship for support. We acknowledge Z. Wu and O. Planes for preliminary work done on this project, as well as D. S. Robson for videography. Additionally, we thank the NMR facility at the University of Cambridge Chemistry Department and the EPSRC UK National Mass Spectrometry Facility at Swansea University for characterization.
The authors declare no competing interests.
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Synthesis and characterization of materials, characterization data, porosity measurements on cage 2, guest uptake experiments and computational modelling.
Flow of the neat-liquid cage 2 material in a 3 mm NMR tube on pushing a reference capillary into the sample.
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Ma, L., Haynes, C.J.E., Grommet, A.B. et al. Coordination cages as permanently porous ionic liquids. Nat. Chem. 12, 270–275 (2020). https://doi.org/10.1038/s41557-020-0419-2
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