Microporous Metal-Organic Framework with Cage-within-Cage Structures for Xenon/Krypton Separation

Separation of Xe/Kr mixtures is of high significance but adaunting task in the chemical industry because of the inert physicochemicalproperties and similar kinetic diameters of Xe and Kr. Herein, a water-resistant metal-organic framework (MOF) JXNU-11(Fe2Ni) featuresdistinctive cage-within-cage structures with small octahedral cagesencapsulated in large cuboctahedral cages. JXNU-11(Fe2Ni) displays ahigh Xe uptake capacity of 124 cm3g-1at 273 K. The breakthroughinterval between Xe and Kr for Xe/Kr (20/80) mixtures is 56 min g-1at273 K, making JXNU-11(Fe2Ni) one of the highest-performing MOF.Additionally, JXNU-11(Fe2Ni) exhibits high Xe productivity for high-purity Xe, good recycling performance, and low regeneration energy inbreakthrough experiments. Computational simulations on JXNU-11-(Fe2Ni) indicate that the preferential site for Xe is the interlayered spacesbetween the octahedral cage and the cuboctahedral cage. The Xe atom isfirmly trapped through extensive Xemiddotmiddotmiddotframework interactions. Thus, the high water stability, high productivity of highly pure Xe,good recyclability, and low regeneration energy of JXNU-11(Fe2Ni) render it a promising adsorbent for actual Xe/Kr separation.