Flexible Crown‐Ether Polyimides Break the K + /Na + Selectivity Barrier in Artificial K + Channels

linker, achieves an unprecedented selectivity of 153.2 ± 5.3. This synergistic combination of ultrahigh selectivity and superior conductance establishes a new benchmark for artificial potassium channels and provides a versatile platform for biomimetic membrane technologies, channel-targeted therapeutics, and biosensing applications.