Field‐Guided Confined Co‐growth Enables Interwoven 2D MOF–Metal Architectures for Selective Ion Transport

ABSTRACT Two‐dimensional confined environments provide unique opportunities to control chemical reactions and crystal growth beyond conventional 3D limits. Here, we report an electric‐field‐directed confined co‐growth strategy that enables the in‐plane stitching of metal‐organic framework (MOF) and silver nanosheets within the interlayers of graphene oxide (GO) membranes. Under spatial confinement, the z ‐axis growth of both crystalline components is suppressed, forcing their evolution along the x–y plane. An applied electric field synchronizes the migration and reduction of Zn ²⁺ , imidazolate ligands, and Ag ⁺ , resulting in lateral propagation and eventual interfacial fusion of MOF and Ag domains into an interwoven 2D network. This confined co‐assembly produces structurally continuous and mechanically reinforced membranes, where interlayer spacing and ion pathways are precisely tuned at the nanoscale. The resulting GO/MOF/Ag membranes exhibit outstanding monovalent/divalent ion selectivity (Li ⁺ /Mg ²⁺ ≈ 9, Na ⁺ /Mg ²⁺ ≈ 13.5, K ⁺ /Mg ²⁺ ≈ 15) with excellent long‐term stability. Beyond ion separation, this work unveils a general paradigm for field‐guided 2D confined synthesis, revealing how growth dimensionality and electric polarization can be coupled to direct the cooperative evolution of distinct crystalline phases. This confined co‐growth mechanism opens a new avenue for designing multi‐component 2D materials with programmable architecture and function.