Conformation‐Adaptive Crown Ether‐Polyimides as Superfast and Exceptionally Selective Artificial Na ⁺ Channels

The development of artificial Na + channels that simultaneously achieve high permeability and high selectivity remains a formidable challenge, as existing systems are constrained by a limited performance ceiling. To address the classical permeability–selectivity trade‐off, we present an adaptive design strategy that moves beyond conventional rigid‐pore architectures. The system is based on a flexible polyimide backbone functionalized with 15‐crown‐5 ionophores via tunable alkyl linkers (C n H 2 n +1 , n = 8–16), enabling efficient Na + permeation through multiple adaptive mechanisms. The conformational plasticity of the architecture facilitates dynamic and cooperative ion coordination during capture and transmembrane transport. The best‐performing transporter, 4 , exhibits a high Na + conductance of 48.9 pS, which is twice that of gramicidin A‐mediated K + transport, together with a record Na + /K + selectivity of 37.8. This work establishes a new benchmark for synthetic ion transporters and opens promising avenues for the development of biomimetic membranes and therapeutic applications.