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 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.