Until recently, organic polymers had not been considered as potential microporous materials as they have enough conformational and rotational freedom to pack space efficiently and therefore do not have high surface areas. However PIMs are highly rigid and contorted macromolecules, which form microporous materials because they cannot pack space efficiently. PIMs are formed by the dibenzodioxane formation reaction between suitable monomers, one of which must contain a site of contortion (e.g. a spiro-center or a rigid non-planar unit). PIMs have potential application in gas storage, membrane separations and heterogeneous catalysis. The monomer CTC (cyclotricatechylene) contains a bowl-shaped cavity which may provide pre-formed micropores of dimensions that are appropriate for gas adsorption. Previous work showed that the dibenzodioxane formation reaction between CTC and 2,3,5,6-tetrafluoroterephthalonitrile gave a yellow, insoluble network polymer with a surface area of 830 m2 g-1 (Scheme 1).
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