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_nH_{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.