Anion-Shielded Porous Organic Cages for High-Performance Xenon/Krypton Separation

The separation of Xe and Kr poses a significant industrial challenge. Herein, we demonstrate an anionic shielding strategy that effectively spatially confines anions within the cage's cavities, constructing unprecedented individually positively charged channel-based adsorbents for Xe/Kr separation. Building on this approach, the obtained POC-TG_Cl achieved high Xe uptake (75.1 cm³ g^-1), remarkably IAST selectivity (23.4), and a record-breaking dynamic selectivity of 15.4 among porous organic materials. These results achieve a superior trade-off between adsorption capacity and selectivity compared to all reported Xe-selective adsorbents. Notably, this is the first Xe/Kr adsorbent to use organic cations as binding sites, offering a new category of adsorbents for Xe/Kr separation. Theoretical calculations and in situ spectroscopic characterizations reveal that the presence of cationic sites accounts for the high performance of POC-TG_Cl. Moreover, unlike conventional ionic materials that are easily affected by water and ion interference, POC-TG_Cl, with its hydrophobic surface and anionic shielding, can effectively prevent the competitive adsorption of water and potential ion exchanges, enabling efficient ppm-level Xe capture from nuclear waste off-gas. Our work not only develops high-performance adsorbents for Xe/Kr separation, but also provides a solution for constructing pure positively charged channels based porous materials for various application.