Biomimetic KcsA channels with ultra-selective K⁺ transport for monovalent ion sieving

Ultra-selective and fast transport of K⁺ are of significance for water desalination, energy conversion, and separation processes, but current bottleneck of achieving high-efficiency and exquisite transport is attributed to the competition from ions of similar dimensions and same valence through nanochannel communities. Here, inspired by biological KcsA channels, we report biomimetic charged porous subnanometer cages that enable ultra-selective K⁺ transport. For nanometer to subnanometer scales, conically structured double-helix columns exhibit typical asymmetric transport behaviors and conduct rapid K⁺ with a transport rate of 94.4 mmol m^-2 h^-1, resulting in the K⁺/Li⁺ and K⁺/Na⁺ selectivity ratios of 363 and 31, respectively. Experiments and simulations indicate that these results stem from the synergistic effects of cation-π and electrostatic interactions, which impose a higher energy barrier for Li⁺ and Na⁺ and lead to selective K⁺ transport. Our findings provide an effective methodology for creating in vitro biomimetic devices with high-performance K⁺ ion sieving.