Robust metal-organic framework with multiple traps for trace Xe/Kr separation

Direct separation of Xe and Kr from air or used nuclear fuel (UNF) off-gas by means of porous adsorbents is of industrial importance but is a very challenging task. In this work, we show a robust metal-organic framework (MOF), namely ECUT-60, which renders not only high chemical stability, but also unique structure with multiple traps. This leads to the ultrahigh Xe adsorption capacity, exceeding most reported porous materials. Impressively, this MOF also enables high selectivity of Xe over Kr, CO₂, O₂, and N₂, leading to the high-performance separation for trace quantitites of Xe/Kr from a simulated UNF reprocessing off-gas. The separation capability has been demonstrated by using dynamic breakthrough experiments, giving the record Xe uptake up to 70.4 mmol/kg and the production of 19.7 mmol/kg pure Xe. Consequently, ECUT-60 has promising potential in direct production of Xe from UNF off-gas or air. The separation mechanism, as unveiled by theoretical calculation, is attributed to the multiple traps in ECUT-60 that affords rigid restrict for Xe atom via van der Waals force.