Hyperselective carbon membranes for precise high-temperature H2 and CO2 separation.

More than 90% of the world's hydrogen (H2) is produced from fossil fuel sources, which requires energy-intensive separation and purification to produce high-purity H2 fuel and to capture the carbon dioxide (CO2) by-product. While membranes can decarbonize H2/CO2 separation, their moderate H2/CO2 selectivity requires secondary H2 purification by pressure swing adsorption. Here, we report hyperselective carbon molecular sieve hollow fiber membranes showing H2/CO2 selectivity exceeding 7000 under mixture permeation at 150°C, which is almost 30 times higher than the most selective nonmetallic membrane reported in the literature. The membrane is able to maintain an ultrahigh H2/CO2 selectivity over 1400 under mixture permeation at 400°C. Pore structure characterization suggests that highly refined ultramicropores are responsible for effectively discriminating the closely sized H2 and CO2 molecules in the hyperselective carbon molecular sieve membrane. Modeling shows that the unprecedented H2/CO2 selectivity will potentially allow one-step enrichment of fuel-grade H2 from shifted syngas for decarbonized H2 production.