Solid‐Like‐Phase Confined Interfacial Polymerization: A Universal Platform for the Controlled 2D Growth of COP Membranes

Abstract The scalable manufacturing of high‐performance covalent organic framework/polymer (COF/COP) membranes faces persistent challenges due to interfacial instability in conventional liquid–liquid interfacial polymerization (LLIP). Here, a transformative solid‐like‐phase confined interfacial polymerization (SLCIP) strategy is developed that synergizes substrate hydration‐induced confinement and functionalization‐enabled monomer anchoring for synthesizing ultrathin two‐dimensional (2D) COP membranes. By orchestrating the hydration barrier and solvent density modulation at functionalized substrates, SLCIP converts the dynamic liquid–liquid interface into a stable solid‒like phase confined interface. This interfacial confinement engineering enables the ambient synthesis of unique ultrathin COP membranes (<40 nm) via confined 2D reaction zones (1.2 nm thickness via MD simulations). The resulting membranes achieve a record water permeance (161 L m⁻ 2 h⁻¹ bar⁻¹, 3.7‐fold enhancement over LLIP), with >98.8% Congo red rejection. Systematic implementation across three solvent systems and five structurally diverse amine monomers demonstrates the universality and chemical adaptability of SLCIP. Industrial scalability is validated through pilot‐scale fabrication of A4‐sized membranes with <5% spatial performance deviation. This work establishes an ambient‐processable interfacial engineering paradigm, offering a sustainable platform for next‐generation molecular separation technologies.