A Synergistic Pore-Engineering Strategy of COF-300 with Missing-Linker Defects and Hydrophobic Surface for Enhanced Furfural/Water Pervaporation Separation

Recently, significant efforts have been dedicated to enhancing the pervaporation performance of polydimethylsiloxane (PDMS) membranes for organic aqueous solutions through the addition of hydrophobic porous particles. However, the approach typically encourages water penetration as well; a phenomenon that goes against the intended goal of separation yet has not garnered the researchers’ focus. Here, a defect engineering strategy was developed to manufacture COF-300/PDMS mixed matrix membranes (MMMs) for promoting organic permeation and simultaneously inhibiting water permeation. Abundant amino groups were generated in situ on the inner walls of COF (covalent organic framework) pores due to the defect of partially missing aldehyde linker during the assembly reaction of amine monomers and mixed aldehyde monomers. The hydrogen bonds formed between water molecules and the exposed amino groups on the inner wall of the COF increase the mass transfer resistance of water molecules. Additionally, tetrafluorobenzaldehyde was used as a substitute for aldehyde monomers on the surface of the COF nanoparticles to enhance their surface hydrophobicity. The combination of pervaporation experiments with adsorption and diffusion simulations revealed that the COF-300 modified by surface hydrophobicity and pore defect engineering enhanced the permeability of furfural while hindering the transport of water.