<p>As an emerging and promising two-dimensional (2D) nanoporous membrane material, the K⁺-cross-linked graphene oxide membrane composed of 2D K⁺-controlled nanochannels (abbreviated herein as K⁺-CLGOM) has recently attracted great attention due to its attractive ion-sieving performance. However, the ion-sieving of K⁺-CLGOM for mono-/mono-valent cations has been still far from satisfactory. In this work, a facile and efficient ion sieving system for mono-/mono-valent cations was built by using the K⁺-CLGOM, which was firstly applied to supported a simple model of semi-biomembrane, namely oil/water (O/W) interface. As-obtained voltammetric results demonstrate that K⁺, NH₄⁺ and Rb⁺ can prefer over Na⁺ and Li⁺ to transfer across K⁺-CLGOM in the trans-membrane system with O/W interface. This work not only provides the membrane-supported O/W interface as a novel platform to explore and understand the ion discrimination of K⁺-CLGOM, but also help to further exploit the potential applications of K⁺-CLGOM in the electrochemical ion sieving and extraction.</p> Graphical abstract <p>Schematic illustration for the preparation process of a K⁺-CLGOM and the mechanism of cation-π interaction between K⁺ and graphene oxide aromatic system.</p> <p></p>