Initial proof-of-principle for near room temperature Xe and Kr separation from air with MOFs

Abstract

SUMMARYMaterials were developed and tested in support of the U.S. Department of Energy's Office of Nuclear Energy, Fuel Cycle Technology Separations and Waste Forms Campaign. Specifically, materials are being developed for the removal of xenon (Xe) and krypton (Kr) from gaseous products of nuclear fuel treatment.During fiscal year 2012, three metal organic framework (MOF) structures were investigated in greater detail for the removal and storage of Xe and Kr from air at room temperature. Breakthrough measurements on a nickel-based MOF indicate this material could capture and separate parts per million by volume (ppmv) levels of Xe (400 ppmv) from air (40 ppmv Kr, 78% N 2 , 21% O 2 , 0.9% Ar, and 0.03% CO 2 ). Similarly, the selectivity of a fluorinated MOF can be changed from Xe > Kr to Xe < Kr simply by changing the temperature over a narrow range (-30 °C). Estimates were made for the cost of bulk quantities of MOFs and compared to other capture materials.

A Two-Column Method for the Separation of Kr and Xe from Process Off-Gases

“…This observation is supported further by molecular simulations in which MOFs, with pore-limiting diameters slightly above the kinetic diameters of Xe and Kr, are shown to have high Xe/Kr selectivities . Among all the MOF materials tested, − Ni/DOBDC and a partially fluorinated MOF with copper (FMOF-Cu) have shown improved Xe and Kr capacities at room temperature relative to previous materials. ,,, Xe at parts per million (ppm) concentrations have been removed from air at room temperature with Ni/DOBDC and FMOF-Cu, and the selectivity of FMOF-Cu was found to change from Xe > Kr to Xe < Kr simply by changing the temperature. − Herein we demonstrate the removal of Xe and Kr from air and from each other with a two-column breakthrough approach at a noncryogenic temperature.…”

Role of Metal Selection in the Radiation Stability of Isostructural M-UiO-66 Metal–Organic Frameworks

“…Many reports discuss thermal, chemical, and mechanical stability of MOFs, yet relatively few examine their radiation stability. ,− Furthermore, results of previous studies are difficult to compare as they are collectively scattered in both MOF selection and irradiation methodology (see Table S1) and could benefit from more systematic approaches with well-defined variables. Pinpoint studies of irradiated MOFs have observed general reduction in crystallinity, surface roughening, and, where accessible, changes in the apparent surface area. ,,, Volkringer et al describe a gamma irradiation study of model MOFsZIF-8, HKUST-1, MILs (MIL-53, MIL-100, and MIL-120), and UiO-66.…”