Hyper-Cross-linked Porous Organic Frameworks with Ultramicropores for Selective Xenon Capture

Exceptionally stable ultramicroporous C-C-bonded porous organic frameworks (IISERP-POF6, 7, 8) have been prepared using simple Friedel-Crafts reaction. These polymers exhibit permanent porosity with a Brunauer-Emmett-Teller surface area of 645-800 m²/g. Xe/Kr adsorptive separation has been carried out with these polymers, and they display selective Xe capture ( s(Xe/Kr) = 6.7, 6.3, and 6.3) at 298 K and 1 bar pressure. Interestingly, these polymers also show remarkable Xe/N₂ ( s(Xe/N₂) = 200, 180, and 160 at 298 K and 1 bar) and Xe/CO₂ selectivity ( s(Xe/CO₂) = 5.6, 7.4, and 5.6) for a 1:99 composition of Xe-N₂/Xe-CO₂. Selective removal of Xe at such low concentrations is extremely challenging; the observed selectivities are higher compared to those observed in porous carbons and metal-organic frameworks. Breakthrough studies were performed using the composition relevant to the nuclear off-gas mixture with the polymers, and we find that the polymers hold Xe for a longer time in the column, which illustrates the Xe/Kr separation performance under dynamic conditions.