Selective anion extraction and recovery using a FeII 4L4 cage

Zhang, Dawei and Ronson, Tanya K. and Mosquera, Jesús and Martinez, Alexandre and Nitschke, Jonathan R. (2018) Selective anion extraction and recovery using a FeII 4L4 cage. Angewandte Chemie - International Edition, 57 (14). pp. 3717-3721. ISSN 1433-7851 (

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Selective anion extraction is useful for the recovery and purification of valuable chemicals, and in the removal of pollutants from the environment. Here we report that FeII 4L4 cage 1 is able to extract an equimolar amount of ReO4 −, a high-value anion and a nonradioactive surrogate of TcO4 −, from water into nitromethane. Importantly, the extraction was efficiently performed even in the presence of 10 other common anions in water, highlighting the high selectivity of 1 for ReO4 −. The extracted guest could be released into water as the cage disassembled in ethyl acetate, and then 1 could be recycled by switching the solvent to acetonitrile. The versatile solubility of the cage also enabled complete extraction of ReO4 − (as the tetrabutylammonium salt) from an organic phase into water by using the sulfate salt of 1 as the extractant.