A metal organic framework based splitter for separating propylene from propane
Separating one organic from another Separating closely related organic molecules is a challenge (see the Perspective by Lin).The separation of acetylene from ethylene is needed in high purity polymer production. Cui et al. developed a copper based metal organic framework with hexafluorosilicate and organic linkers designed to have a high affinity for acetylene. These materials, which capture four acetylene molecules in each pore, successfully separated acetylene from mixtures with ethylene. Propane and propylene are both important feedstock chemicals. Their physical and chemical similarity, however, requires energy intense processes to separate them. Cadiau et al. designed a fluorinated porous metal organic framework material that selectively adsorbed propylene, with the complete exclusion of propane. Science, this issue pp. 141 and 137; see also p. 121 A tailored metal organic framework material is able to separate propane from propylene. The chemical industry is dependent on the olefin/paraffin separation, which is mainly accomplished by using energy intensive processes. We report the use of reticular chemistry for the fabrication of a chemically stable fluorinated metal organic framework (MOF) material (NbOFFIVE 1 Ni, also referred to as KAUST 7) The bridging of Ni(II) pyrazine square grid layers with (NbOF5)2 pillars afforded the construction of a three dimensional MOF, enclosing a periodic array of fluoride anions in contracted square shaped channels. The judiciously selected bulkier (NbOF5)2 caused the looked for hindrance of the previously free rotating pyrazine moieties, delimiting the pore system and dictating the pore aperture size and its maximum opening. The restricted MOF window resulted in the selective molecular exclusion of propane from propylene at atmospheric pressure, as evidenced through multiple cyclic mixed gas adsorption and calorimetric studies.
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