Polymers of Intrinsic Microporosity Derived from Bis(phenazyl) Monomers Bader S. Ghanem, ² Neil B. McKeown,* ,² Peter M. Budd, ‡ and Detlev Fritsch § School of Chemistry, Cardiff UniVersity, Cardiff, CF10 3AT, U.K., Organic Materials InnoVation Centre, School of Chemistry, UniVersity of Manchester, Manchester, M13 9PL, U.K., and Institute of Polymer Research, GKSS Research Centre Geesthacht GmbH, Max-Planck-Strasse 1, D-21502 Geesthacht, Germany ReceiVed August 15, 2007; ReVised Manuscript ReceiVed December 11, 2007 ABSTRACT: Novel polymers of intrinsic microporosity (PIMs) are prepared from bis(phenazyl) monomers derived from readily available bis(catechol)s. One of the polymers (termed PIM-7) has an excellent combination of properties with high internal surface area, good film-forming characteristics, and gas transport properties that make it a suitable candidate for gas separation membranes. The high gas permeability and good ideal selectivity of PIM-7 place it above Robeson’s upper-bound for a number of commercially important gas pairs (e.g., O 2 /N 2 , CO 2 /CH 4 , and CO 2 /N 2 ). Introduction Microporous materials, such as zeolites or activated carbons, contain interconnected molecular-sized pores (<2 nm) and are of great value as heterogeneous catalysts and adsorbents. Most polymers do not form solids that display classical microporosity because their conformational mobility allows the constituent macromolecules to fill space efficiently. However, microporous polymer-based materials can be obtained by the extensive crosslinking of solvent swollen polymers (e.g., hypercrosslinked polystyrenes) 1,2 or by preparing polymer networks using rigid monomers. 3-10 In addition, certain highly rigid, non-network polymers, for example poly(trimethylsilylpropyne), 11,12 certain polyimides, 13 and a number of fluorinated polymers, 14 form solids with very large free volumes so that they too can behave as microporous materials. These high-free volume polymers are soluble and, therefore, can be processed into forms that are useful as membranes for gas separations and water purification. Recently, we have described a novel class of high-free volume polymer termed polymers of intrinsic microporosity (PIMs) that are composed of rigid and contorted macromolecules, wholly composed of fused-rings some of which are spirocyclic. 15-19 PIMs form microporous organic materials due to their inability to pack space efficiently. PIMs combine high internal surface areas with the synthetic diversity of step-growth polymers and can be used for a wide range of applications including heterogeneous catalysis, 10,19 membrane separations, 15,20 hydro- gen storage, 6,7,21,22 and the adsorption of organic compounds. 10,23 The archetypal PIM, termed PIM-1 (Scheme 1), is prepared as a high molecular mass, soluble polymer from the dioxane- forming reaction between commercially available 5,5′,6,6′- tetrahydroxy-3,3,3′,3′-tetramethyl-1,1′-spirobisindane (monomer 1) and 2,3,5,6-tetrafluoroterephthalonitrile, which is an efficient double aromatic nucleophilic substitution reaction (S N Ar). 15,16 The spiro-center (i.e., a single tetrahedral carbon atom shared by two rings) of monomer 1 provides the site of contortion necessary for solubility and microporosity. On reprecipitation, PIM-1 provides microporous powder with a surface area of 780 m 2 g -1 and can be cast from solution into robust free-standing films that show great promise for gas separations. 20 A number of other bis(catechol) monomers have also been used for PIM synthesis (PIMs-2-6) 16 but there are no readily available tetrahalide monomers that contain spiro-centers to provide a suitable site of contortion. This paper describes the simple synthesis of suitably reactive tetrachloride monomers 4 and 5 based on phenazine units prepared directly from suitable bis- (catechol) monomers such as 1 and 2,3,6,7-tetrahydroxy-9,10- dimethyl-9,10-ethanoanthracene 2. The properties and potential applications of the PIMs (PIMs-7-10) derived from these novel monomers are discussed (Scheme 2). In addition, the properties of two novel “cardo” polymers (Cardo-PIMs 1 and 2) derived from the phenazyl monomers and 9,9-bis(3,4-hydroxyphenyl)- fluorene 3 are compared to the PIMs that contain fully fused- ring structures. Experimental Section Materials and Methods. All materials including monomer 1 (5,5′,6,6′-tetrahydroxy-3,3,3′,3′-tetramethyl-1,1′-spirobisindane) were obtained from Aldrich Chemical Co. or Lancaster Synthesis Ltd. and were used without purification. Monomer 2 (2,3,6,7-tetrahy- droxy-9,10-dimethyl-9,10-ethanoanthracene) was prepared from catechol and 2,5-hexanedione following a literature procedure. 24-26 Monomer 3 (9,9-bis(3,4-dihydroxyphenyl)fluorene) was prepared * To whom correspondence should be addressed. Prof. Neil B. McKeown, E-mail, mckeownnb@cardiff.ac.uk; Phone, +44 (0)2920- 875851, School of Chemistry, Cardiff University, Cardiff, CF10 3AT, U.K. ² Cardiff University. ‡ University of Manchester. § GKSS Research Centre Geesthacht GmbH. Figure 1. The structure of monomer 4 (a) face on and (b) in the plane, as determined from a single-crystal X-ray diffraction study showing the site of contortion provided by the spiro-center. (Raftery, J.; Ghanem, B. S.; McKeown, N. B. Report in preparation). 1640 Macromolecules 2008, 41, 1640-1646 10.1021/ma071846r CCC: $40.75 © 2008 American Chemical Society Published on Web 02/12/2008