Selective Permeability of Uranyl Peroxide Nanocages to Different Alkali Ions: Influences from Surface Pores and Hydration Shells

The precise guidance to different ions across the biological channels is essential for many biological processes. An artificial nanopore system will facilitate the study of the ion-transport mechanism through nanosized channels and offer new views for designing nanodevices. Herein we reveal that a 2.5 nm-sized, fullerene-shaped molecular cluster Li48+mK12(OH)(m)[UO2(O-2)(OH)](60-) (H2O)(n) (m approximate to 20 and n approximate to 310) (U60) shows selective permeability to different alkali ions. The subnanometer pores on the water-ligand-rich surface of U-60 are able to block Rb+ and Cs+ ions from passing through, while allowing Na+ and K+ ions, which possess larger hydrated sizes, to enter the interior space of U-60. An interestingly high entropy gain during the binding process between U-60 and alkali ions suggests that the hydration shells of Na+/K+ and U-60 are damaged during the interaction. The ion selectivity of U-60 is greatly influenced by both the morphologies of the surface nanopores and the dynamics of the hydration shells.