Potassium‐Selective Covalent Organic Framework Membranes Enable Dynamic Monitoring of Microbial K ⁺ Metabolism

Abstract Ultraselective and rapid transport of potassium ion (K ⁺ ) is crucial for maintaining life activities such as osmotic pressure equilibrium, protein synthesis regulation, microbial growth, and communication. However, it is challenging to achieve high efficiency and precise K ⁺ transport due to the existence of competitive cations with similar size and valence. Here, a biomimetic K ⁺ nanochannel based on sulfonated covalent organic frameworks (COF) is reported with high K ⁺ screening selectivity to achieve dynamic microbial K ⁺ metabolism monitoring. Similar to the structure and function of biological KcsA channels, sulfonated COF feature ordered nanochannels and abundant surface charges, facilitating effective sieving of K ⁺ and sodium ions (Na ⁺ ) through size screening and electrostatic interactions, achieving a K ⁺ /Na ⁺ selectivity ratio of 17.3. Molecular dynamic simulations indicate that the K ⁺ /Na ⁺ selectivity of the COF nanochannels arises from the interaction of K ⁺ with the sulfonate functional groups on the nanochannels, resulting in a decreased energy barrier for K ⁺ . Given the excellent K ⁺ screening selectivity and efficiency, the designed COF nanochannels enable real‐time monitoring of K ⁺ in complex microbial systems and provide guidance for the synthesis of high value‐added products. These findings suggest approaches for developing efficient and selective nanochannels for ion separation, nanofluidic, and complex microbial metabolism systems.