Ultramicroporous carbon molecular sieve membrane derived from hyper-crosslinked ionic polymers for efficient H₂/CO₂ separation

Carbon molecular sieve membranes (CMSMs) are a class of porous membranes inherited with excellent thermal stability, high tolerance and superior mechanical strength. Owing to their nanoporous structures, CMSMs usually hold significant potential for gas separation applications. Specifically, hyper-crosslinked ionic polymer (HIP) membranes possess a highly crosslinked nitrogen-rich framework, high thermal stability together with exceptional mechanical strength, making them excellent precursors for the CMSMs fabrication. Upon pyrolysis of HIP membranes, the resulting CMSMs featured with nitrogen functional sites exhibit strong interactions with CO₂, which significantly reduces the CO₂ permeability while other gas molecules continue to flow through the nanoporous membrane. The resultant CMSMs exhibited excellent H₂/CO₂ selectivity with values of 10.75 and 7.09, together with ultra-high H₂ permeability of 3052 and 9181 barrer, respectively, surpassing the Robeson upper bound. The preparation route towards CMSMs with high nitrogen content from HIP can significantly enrich the rational design and synthesis strategies of high-performance gas separation CMSM materials.