Nanoarchitectonics of carbon molecular sieve membranes with graphene oxide and polyimide for hydrogen purification

Abstract

Hydrogen is an important energy carrier for the transition to a carbon-neutral society, the efficient separation and purification of hydrogen from gaseous mixtures is a critical step for the implementation of a hydrogen economy. In this work, graphene oxide (GO) tuned polyimide carbon molecular sieve (CMS) membranes were prepared by carbonization, which show an attractive combination of high permeability, selectivity and stability. The gas sorption isotherms indicate that the gas sorption capability increases with the carbonization temperature and follows the order of PI–GO-1.0%-600 °C > PI–GO-1.0%-550 °C > PI–GO-1.0%-500 °C, more micropores would be created under higher temperatures under GO guidance. The synergistic GO guidance and subsequent carbonization of PI–GO-1.0% at 550 °C increased H₂ permeability from 958 to 7462 Barrer and H₂/N₂ selectivity from 14 to 117, superior to state-of-the-art polymeric materials and surpassing Robeson's upper bound line. As the carbonization temperature increased, the CMS membranes gradually changed from the turbostratic polymeric structure to a denser and more ordered graphite structure. Therefore, ultrahigh selectivities for H₂/CO₂ (17), H₂/N₂ (157), and H₂/CH₄ (243) gas pairs were achieved while maintaining moderate H₂ gas permeabilities. This research opens up new avenues for GO tuned CMS membranes with desirable molecular sieving ability for hydrogen purification.