Precise Hydrogen Sieving by Carbon Molecular Sieve Membranes Derived from Solution-Processable Aromatic Polyamides

Aromatic polyamides (aramids) are broadly used to manufacture desalination membranes; however, they are rarely considered for gas separation. Here, we report precise hydrogen sieving in ultramicroporous carbon molecular sieve (CMS) membranes derived from an uncrosslinked aramid synthesized by stirred interfacial polymerization of diamine and mixed diacid chloride monomers. While hydrogen bonds gave the aramid precursor unattractive separation performance, they were leveraged to provide aramid-derived CMS membranes with ultrahigh H2/CO2 selectivity exceeding all known CMS membranes. Adsorption in aramid-derived CMS membranes suggested their ultrahigh H2/CO2 selectivity was attributable to diffusion selectivity above 3000. The excellent solution processability of uncrosslinked aramids allowed the fabrication of scalable CMS hollow fiber membranes. The findings of this work open the door to a new class of highly selective CMS membranes for H2 separation and CO2 capture.