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

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.