Finely Tuning the Free Volume Architecture in Iptycene-Containing Polyimides for Highly Selective and Fast Hydrogen Transport

Iptycene-based polyimides have attracted extensive attention recently in the-membrane gas separation field due to their unique, structural hierarchy and chemical characteristic that enable construction of well-defined yet tailorable free volume architecture for fast and selective molecular transport. We report here a new series of iptycene-based polyimides that are exquisitely tuned in the Monomer structure to afford preferred microcavity architecture for hydrogen transport. In particular, a triptycene-containing dianhydride (TPDAn) was prepared to react with two iptycene-containing diamines (i.e., TPDAm and PPDAm) or 2,2'-bis(3-amino-4-hydroxyphenyl)hexafluoropropane (6FAP) to produce entirely or partially iptyocene-based polyimides. The, incorporation, of iptycene units effectively disrupted chain packing, which resulted in ultrafine microporosity in the membranes with a desired bimodal size distribution with maxima at similar to 3 and similar to 7 angstrom, respectively. Depending on the combination of diamine and dianhydride, the microporosity was feasibly tuned and optimized to meet the needs of challenging H-2 separations) especially for H-2/N-2 and H-2/CH4 gas pairs. Particularly, a H-2 permeability of 27 barrers and H-2/N-2 and H-2/CH4 selectivities of 142 and 300, respectively, were obtained for TPDAn-6FAP.