Superspreading‐Confined Assembly of Oriented 2D MOF Membranes for Biomimetic Cation‐Regulated Ion Transport

Abstract Inspired by biological channels, metal‐organic framework (MOF) membranes with sub‐nanometer sized channels offer an ideal platform to construct high‐performance artificial nanofluidic system. However, fabricating long‐range ordered MOF membranes is still a significant challenge. Herein, a superspreading‐confined assembly method is developed to prepare large‐scale oriented 2D MOF (Zn‐TCPP (TCPP = meso‐tetra(4‐carboxyphenyl) porphine)) membranes. The superspreading of reactant liquid under oil phase to form liquid layer plays a critical role in membrane formation, which provides a dynamic confined space for layered assembly of Zn‐TCPP nanosheets. Accompanied with solvent diffusion, such liquid layer is completely converted into <001>‐oriented MOF membrane with controlled thickness. The prepared membrane exhibits distinct divalent cation (M_x²⁺)‐regulated ion transport behavior as that demonstrated in biological channels: K⁺ flux can be precisely adjusted by anchoring diverse M_x²⁺ ions to binding sites, which is appealing in designing high‐performance nanofluidic iontronics. Moreover, similar strategies can be employed to fabricate other MOF membranes (such as Hf‐BTB (BTB = 1,3,5‐tris(4‐carboxyphenyl)benzene) and Ni‐TCPE (TCPE = tetrakis(4‐carboxyphenyl)ethylene)), indicating the broad applicability of this method in 2D membrane fabrication.