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

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.