Solution-processible polymers of intrinsic microporosity (PIMs) are appealing materials for membrane applications due to their chemical and structural variety available from a wide range of PIM building blocks and significantly improved gas separation performance compared to conventional low-free-volume glassy polymers. This review highlights recent materials design developments in PIMs including: (i) benzotriptycence-based ladder PIMs, (ii) norbornyl-benzocyclobutene-based PIMs made by catalytic arene-norbornene annulation (CANAL), (iii) high-performance functionalized PIMs (iv) PIM-based thin-film composite membranes, and (v) PIM-based carbon molecular sieve (CMS) membranes. Significant advances in gas separation properties of new generation PIMs have set the recent 2015 H2/N2, H2/CH4, and O2/N2 upper bounds, 2018 CO2/CH4 mixed-gas upper bound, and 2019 pure-gas CO2/N2 and CO2/CH4 pure-gas upper bounds. Realizing the full potential of PIMs for future commercial use requires further improvements in (i) gas-pair selectivity, especially for challenging separations, (ii) stability against physical aging and plasticization, (iii) polymer scale-up, and (iv) reproducible membrane fabrication.
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