(261h) A Nature-Inspired Design of a Double-Layer Graphene Membrane Module for Potassium Ion Transport

The nature-evolved protein KcsA transports potassium with not only a high-speed up to 10⁸ ions/s, and, moreover, high selectivity in terms of K⁺/Na⁺ selectivity ratio up to 1000:1. The functional structure region (selective filter, SF) of KcsA is a four-layer cylindrical nanopore with a length of about 1.2 nm and an inner diameter of 0.3 nm, with a conserved sequence of TVGYG. Recently, we designed a graphene membrane module and demonstrated a solution-mixed power generation model that can obtain a power density of up to 1280 w/m² by separating potassium ions from chloride ions in a solution with a porosity of less than 1%.

In this work, we proposed a carbonyl-modified double-layer graphene nanopore structure mimicking the SF region of the KcsA protein. Our results show that the four carbonyl-modified sites rotating between the double layers can achieve potassium ion selectivity, with a dynamic K⁺/Na⁺ selectivity ratio of up to 1295, and a potassium ion transport rate of 3.5 × 10⁷ ions/s, which is close to that of the KcsA. Moreover, the simulation has shown a double-ion transfer mode of potassium ions, which reproduced the previously discovered knock-on mechanism. The present work offered a molecular insight of the biomimetic ion-selective nanostructures, which is helpful for the design and application of ion-selective membrane materials and modules.