Hyperselective carbon membranes for precise high-temperature H and CO separation.

More than 90% of the world's hydrogen (H) is produced from fossil fuel sources, which requires energy-intensive separation and purification to produce high-purity H fuel and to capture the carbon dioxide (CO) by-product. While membranes can decarbonize H/CO separation, their moderate H/CO selectivity requires secondary H purification by pressure swing adsorption. Here, we report hyperselective carbon molecular sieve hollow fiber membranes showing H/CO 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 H/CO 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 H and CO molecules in the hyperselective carbon molecular sieve membrane. Modeling shows that the unprecedented H/CO selectivity will potentially allow one-step enrichment of fuel-grade H from shifted syngas for decarbonized H production.