Macrocyclic Pyridone Pentamers for Highly Selective High-Capacity Removal of Caesium Ions from Radioactive High-Salinity Waste.

We report here that macrocyclic H-bonded pyridone pentamers, containing five properly and convergently spaced electron-rich O-atoms that decorate a rigid cavity of 2.85 Å across, exhibit an extraordinarily high yet pH-independent capacity and selectivity in Cs+ removal. In particular, with [host]=240 μM and [Cs+ ]=15 μM, a single extraction efficiently removes more than 91% of Cs+ ions from artificial sea water, containing various competitive metal ions at a total concentration of 0.68 M ([total Mn+ ]/[Cs+ ]=4.5×104 ]). To our best knowledge, these pyridone pentamers represent the best small organic molecule-based extractants that target Cs+ ions.