A highly selective superphane for ReO4− recognition and extraction
Wei Zhou, Aimin Li, Philip A. Gale, Qing He
Abstract
Highly selective anion recognition and extraction is challenging and yet critical for removal of pollutants from the environment and the effective recovery of valuable chemicals from low-content (at sub-ppm or ppb level) sources. In this paper, we detail the gram-scale synthesis of a superphane 2, an anion receptor that selectively binds ReO4−. Superphane 2 can extract perrhenate from solid mixtures containing traces of ReO4− anion (as low as 200 ppb) and aqueous media with near 100% selectivity over large excesses of competing anions. Meanwhile, up to 99.99% of ReO4− can be separated from complex simulated aqueous waste streams containing ppm-level perrhenate via either liquid-liquid extraction or simple column adsorption. Importantly, after extraction or adsorption, superphane 2 can be recycled and reused by simple treatment with aqueous NaHCO3.