Coordination cages as permanently porous ionic liquids.

Abstract

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.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. (EPSRC DTP grant EP/M508007/1) acknowledges the Engineering and Physical Sciences Research Council for funding. L.L. acknowledges an EPSRC Departmental Studentship. A.W. and A.R.S. acknowledge the National Centre for Research and Development for funding (LIDER/024/391/L-5/13/NCBR/2014 and PRELUDIUM UMO-2016/21/N/ST5/00851). T.D.B. would like to thank the Royal Society for a University Research Fellowship (UF150021), and for a Research Grant (RSG\R1\180395)