Artificial sodium-selective ionic device based on crown-ether crystals with subnanometer pores

Biological sodium channels ferry sodium ions across the lipid membrane while rejecting potassium ions and other metal ions. Realizing such ion selectivity in an artificial solid-state ionic device will enable new separation technologies but remains highly challenging. In this work, we report an artificial sodium-selective ionic device, built on synthesized porous crown-ether crystals which consist of densely packed 0.26-nm-wide pores. The Na⁺ selectivity of the artificial sodium-selective ionic device reached 15 against K⁺, which is comparable to the biological counterpart, 523 against Ca^2 +, which is nearly two orders of magnitude higher than the biological one, and 1128 against Mg^2 +. The selectivity may arise from the size effect and molecular recognition effect. This work may contribute to the understanding of the structure-performance relationship of ion selective nanopores.