Ultra‐selective carbon molecular sieve membranes derived from carboxylated <scp>polymers of intrinsic microporosity</scp> for hydrogen and air separation

Abstract Carbon molecular sieve (CMS) membranes hold significant potential for advanced gas separation and purification, yet further improvements in molecular sieving properties remain a critical challenge. In this study, carboxylated‐PIM‐1 (PIM‐COOH) polymers were synthesized by hydrolyzing PIM‐1 polymers, serving as efficient precursors for CMS membrane fabrication. The pyrolysis process was optimized, with the temperature tuned to 800°C for 2 h, resulting in high‐performance CMS membranes. These membranes demonstrated exceptional gas separation capabilities, achieving H 2 and O 2 permeabilities of 831.8 and 79.7 Barrer, respectively, with H 2 /CH 4 and O 2 /N 2 selectivities of 453.6 and 12.8, surpassing the latest 2015 upper bound for H 2 /CH 4 and O 2 /N 2 separation. Mixed gas tests further validated the single‐gas results, revealing H 2 /CH 4 and O 2 /N 2 selectivities as high as 1402.1 and 16.8, respectively. This innovative strategy, leveraging PIM‐COOH‐derived CMS membranes, provides a promising pathway for next‐generation hydrogen purification and air separation technologies.