Dynamic separation of Xe and Kr by metal-organic framework and covalent-organic materials： a comparison with activated charcoal

We systematically investigate dynamic separation of Xe and Kr at room temperature using four representative porous materials （Cu-BTC, ZIF-8, COP-4 and activated carbon （AC））. Results indicate that among the four materials, Cu-BTC not only shows the highest retention volume per gram （Vg=788 mL g-1, which is 1.8 times of activated carbon （436 mL g-1）） under flowing condition, but also can separate 350 ppm Xe from 35 ppm Kr mixture in air with a high Xe/Kr selectivity of 8.6 at room tem- perature and 200 kPa, due to its suitable pore morphology, open metal sites, small side pockets in the framework. Moreover, the Cu-BTC also performs well on individual separation of Xe, Kr, CO2 from five-component gas mixture （Xe：Kr：CO2：Ar：N2= 1：1：1：1：0.5, V/V） and has the longest retention time for Xe （20 min） in gas chromatographic separation, suggesting that it is a good candidate for potential applications as polymeric sieves.