Highly Selective Anion Recognition, Extraction and Deep Removal Using a Superphane

Highly selective anion recognition and extraction are critical and challenging to deep removal of pollutants from the environment and effective recovery of valuable chemicals from low–content (at sub–ppm or ppb level) sources. Herein, we detail the gram–scale synthesis of a superphane 2, a new supramolecular host that was found capable of encapsulating ReO4– with high selectivity, as suggested by the single–crystal structures, NMR spectroscopy and theoretical calculations. Under solid–liquid extraction condidtions, 2 proved able to extract perrhenate from the solid mixture containing trace ReO4– (as low as 200 ppb) with near 100% selectivity over other 7 competing anions. Under liquid–liquid extraction conditions, using 2 as the supramolecular extractant, over 99.99% of ReO4– could be separated from the complex simulated aqueous waste streams containing ppm–level perrhenate and large excess of competing ions. Notably, after extraction, 2 could be recycled and reused by simple treatment with NaHCO3. This study opens up the door to development of superphane–based advanced materials for deep elimination of pollutants from the envirenment and purification of chemicals of interest with high efficiency and selectivity.