Assembly-Dissociation-Reconstruction Synthesis of Covalent Organic Framework Membranes with High Continuity for Efficient CO2 Separation

Covalent organic frameworks (COFs), at the forefront of porous materials, hold tremendous potential in membrane separation; however, achieving high continuity in COF membranes remains crucial for efficient gas separation. Here, we present a unique approach termed assembly-dissociation-reconstruction for fabricating COF membranes tailored for CO₂/N₂ separation. A parent COF is designed from two-node aldehyde and three-node amine monomers and dissociated to high-aspect-ratio nanosheets. Subsequently, COF nanosheets are orderly reconstructed into a crack-free membrane by surface reaction under water evaporation. The membrane exhibits high crystallinity, open pores and a strong affinity for CO₂ adsorption over N₂, resulting in CO₂ permeance exceeding 1060 GPU and CO₂/N₂ selectivity surpassing 30.6. The efficacy of this strategy offers valuable guidance for the precise fabrication of gas-separation membranes.