Selective sorbent traps xenon and krypton

By using computational methods, a multi-institutional research team has analyzed chemical and physical properties of 125,000 porous metal-organic framework (MOF) materials and found that one of them is exceptionally good at separating xenon and krypton from gas mixtures. The team then confirmed that prediction experimentally (Nat. Commun. 2016, DOI: 10.1038/ncomms11831). Xenon and krypton, along with oxygen, nitrogen, carbon dioxide, and other gases, are evolved when spent nuclear fuel is reprocessed to extract valuable fissile material. Reprocessing facilities trap and separate the ­gases, which include radioactive isotopes, via cryogenic distillation. But that approach is energy-intensive and expensive. Looking for a better option, Praveen K. Thallapally of Pacific Northwest National Laboratory and coworkers searched for sorbents that could selectively trap and separate xenon and krypton during fuel reprocessing. Nonradioactive xenon could be used for commercial lighting, imaging, and other applications, whereas the recovered krypton contains long-lived isotopes and must be sequestered. The team identified SBMOF-1, a MOF made from calcium ions and sulfonyldibenzoate linkers, as the best candidate. The team found that SBMOF-1 exhibits the highest xenon adsorption capacity for a MOF and an exceptional ability to separate xenon and krypton from each other and from the other gases by size exclusion.