Infiltration of COF/PDMS composite coating into porous PVDF membrane: Toward high-permeability alcohol-water separation

To construct a pervaporation alcohol-water separation membrane with high adsorption and dissolution selectivity, as well as fast internal transport channels, covalent organic framework (COF)/PDMS mixed matrix membranes were prepared. The selected hydrophobic fluorine-containing COF, TAPB-TFA, is purely organic, has a uniform spherical shape, and exhibits excellent interfacial compatibility with the PDMS. The TAPB-TFA/PDMS coating was casted into the porous PVDF membrane to form a compact inner selective layer. Meanwhile, the rough surface with honeycomb-like folds of the PVDF membrane was quite preserved, enhancing the hydrophobicity of the membrane surface. This structure provides numerous solvent adsorption sites for alcohols while effectively inhibiting the passage of water. Simultaneously, TAPB-TFA has a well-defined pore structure, offering numerous channels for the rapid transport of alcohols, thereby enhancing their diffusion rates. The flux of the optimized TAPB-TFA/PDMS@PVDF membrane was 4.52 ± 0.13 kg·m −2 ·h −1 with a high separation factor of 10.9 ± 0.32 for 5 wt% ethanol aqueous solution.