A covalent organic framework membrane with highly selective and permeable artificial sodium channels via ion recognition

Biological sodium channels efficiently discriminate between same-charge ions with similar hydration shells. However, achieving precise ion selectivity and high throughput in artificial ion channel fabrication remains challenging. Here, we investigate angstrom-scale channels in 15-crown-5 (15C5) functionalized COF membranes for fast, selective ion transport. Due to crown ether recognition of sodium ions, channels in DHTA-Hz-15C5 membranes selectively facilitate Na⁺ transport, further enhanced by the hydroxyl-enriched COF skeleton. A Na⁺/K⁺ selectivity of 58.31 is achieved with 9.33 mmol m^-2 h^-1 permeance, significantly exceeding current membranes and resembling biological channels. Theoretical simulations indicate one-dimensional COF channels facilitate transport, while crown ether recognition makes the Na⁺ energy barrier significantly lower than K⁺, enabling ultrahigh selectivity with high Na⁺ permeability. This promotes COFs for efficient single-ion transport and advances crown ether ion selectivity in nano-restricted environments.