Diffusion/Modulator Dual‐Mediated Solid‐Liquid/Vapor Interfacial Synthesis of Crystalline Covalent Organic Framework Membranes

Constructing oriented crystalline covalent organic framework (COF) membranes with controllable thickness for water purification is highly desirable. Herein, we present a simple and universal protocol to prepare high‐quality COF membranes on the inner wall of a glass vessel using a diffusion/modulator dual‐mediated solid‐liquid/vapor interfacial synthesis strategy. By meticulous control of the solvent and temperature, a thin supersaturated spreading liquid layer was formed on the glass wall surface and served as a confined microreactor for incubating crystal nuclei. This induced the aniline‐modulated solid‐liquid/vapor interfacial exchange reaction and upward growth of a highly ordered COF membrane. The experiments and theoretical simulations revealed the underlying mechanisms of solid‐liquid/vapor interfacial nucleation, growth and crystallization. Using this strategy, we created 13 types of new, free‐standing, imine‐linked COF membranes with exceptional performances in crystallinity, porosity, stability, processability and adsorption capacity. As an application demonstration, a COF membrane‐filled filter was coupled with high‐performance liquid chromatography system for the automated removal of multitarget liquid‐crystal monomers in real water samples (removal efficiency ≥ 96%). This study enriches the synthesis toolboxes of COF membranes and broadens their application scopes.