1.D.184.  Ion-selective Crown-ether Crystal Pore (IS-CE-P) Family

Artificial solid-state ionic devices enable separation technologies. Ye et al. 2021 reported 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 ⁺ (comparable to the biological counterpart, 523 against Ca²⁺) 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.

Crown ethers (CEs) are widely studied in the area of artificial ion channels owing to their intrinsic host-guest interaction with different kinds of organic and inorganic ions. Other advantages such as lower price, chemical stability, and easier modification also make CEs a research hotspot in the field of synthetic transmembrane nanopores. Numerous CE-based membrane-active synthetic ion channels have been designed and fabricated in the past, but progress of CEs-based synthetic ion transporters has been  reviewed, including their design principles, functional mechanisms, controllable properties, and biomedical applications (He et al. 2023).

Xin et al. 2025 have synthesized bis (cholesterol-dibenzo-18-crown-6-ether)-pillar[5]arene compound 1 through a click reaction.  It could spontaneously insert into lipid bilayers to form an ion channel due to the membrane anchor cholesterol group. It shows significant transport activity of K⁺ over Na⁺, with a permeability ratio of K⁺/Na⁺ equal to 4.58. Compound 1 two crown ether modules act as selective filters similar to natural K⁺ channels, which are determined to 1 : 2 binding stoichiometry to K⁺ by Job's plot and NMR titration. This structurally unambiguously unimolecule artificial channel provides ideas for constructing highly K⁺/Na⁺ selective molecular filters.