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

Abstract

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.