A highly gas permeable polymer with exceptional size selectivity is prepared by fusing triptycene units together via a polymerization reaction involving Tröger's base formation. The extreme rigidity of this polymer of intrinsic microporosity (PIM‐Trip‐TB) facilitates gas permeability data that lie well above the benchmark 2008 Robeson upper bounds for the important O2/N2 and H2/N2 gas pairs.
Nitrile groups in the polymer of
intrinsic microporosity PIM-1
were reduced to primary amines using borane complexes. In adsorption
experiments, the novel amine–PIM-1 showed higher CO2 uptake and higher CO2/N2 sorption selectivity
than the parent polymer, with very evident dual-mode sorption behavior.
In gas permeation with six light gases, the individual contributions
of solubility and diffusion to the overall permeability was determined
via time-lag analysis. The high CO2 affinity drastically
restricts diffusion at low pressures and lowers CO2 permeability
compared to the parent PIM-1. Furthermore, the size-sieving properties
of the polymer are increased, which can be attributed to a higher
stiffness of the system arising from hydrogen bonding of the amine
groups. Thus, for the H2/CO2 gas pair, whereas
PIM-1 favors CO2, amine–PIM-1 shows permselectivity
toward H2, breaking the Robeson 2008 upper bound.
Introducing the highly rigid ethanoanthracene unit into polyimides of intrinsic microporosity provides an impressive enhancement of gas selectivity by molecular sieving.
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