Supramolecular Assembly\nof One-Dimensional Coordination\nPolymers for Efficient Separation of Xenon and Krypton

Abstract

Efficient separation and purification of xenon (Xe) from\nkrypton\n(Kr) represent an industrially crucial but challenging process. While\nthe adsorption-based separation of these atomic gases represents an\nenergy-efficient process, achieving highly selective adsorbents remains\na difficult task. Here, we demonstrate a supramolecular assembly of\ncoordination polymers, termed as M(II)-dhbq (M = Mg, Mn, Co, and Zn;\ndhbq = 2,5-dihydroxy-1,4-benzoquinone), with high-density open metal\nsites (5.3 nm^–3) and optimal pore size (5.5 Å),\nwhich are able to selectively capture Xe among other chemically inert\ngases including Kr, Ar, N₂, and O₂. Among M(II)-dhbq\nmaterials, Mn-dhbq exhibits the highest Xe uptake capacity of 3.1\nmmol/g and a Xe/Kr selectivity of 11.2 at 298 K and 1.0 bar, outperforming\nmany state-of-the-art adsorbents reported so far. Remarkably, the\nadsorption selectivity of Mn-dhbq for Xe/O₂, Xe/N₂, and Xe/Ar at ambient conditions reaches as high as 70.0, 139.3,\nand 64.0, respectively. Direct breakthrough experiments further confirm\nthat all M(II)-dhbq materials can efficiently discriminate Xe atoms\nfrom other inert gases. It is revealed from the density functional\ntheory calculations that the strong affinity between Xe and the coordination\npolymer is mainly attributed to the polarization by open metal sites.