A highly selective superphane for ReO4− recognition and extraction

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 ReO 4 − . Superphane 2 can extract perrhenate from solid mixtures containing traces of ReO 4 − 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 ReO 4 − 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 NaHCO 3 . • A superphane for highly selective recognition of ReO 4 − is synthesized in gram scale • Over 99.99% of ReO 4 − can be separated from complex simulated waste streams • Rapid removal of ppb-level ReO 4 − is achieved via extraction or column adsorption • The superphane for ReO 4 − extraction/adsorption can be recycled and reused Extraction of low concentrations of rhenium anions from waste streams is important industrially. Zhou et al. present the facile and gram-scale synthesis of a superphane via dynamic imine chemistry coupled with NaBH 4 reduction, which can separate perrhenate from low-content mixtures and simulated Hanford waste streams with exceptionally high efficiency and selectivity, along with good recyclability and reusability.