In situ assembly of a covalent organic framework composite membrane for dye separation

Covalent organic frameworks (COFs) are prominent candidates for water separations and treatment. They have ordered channel structures, low densities, large specific surface areas, and tunable pore sizes. These features can be used to construct advanced organic solvent nanofiltration and separation membranes. Here, membranes with high permeability and selectivity are prepared in situ with 10% 1,3,5‒triformylphloroglucinol (Tp) and 4,4′,4″- (1,3,5- triazine-2,4,6-triyl) trianiline (TTA) on a Noria−polyethyleneimine co-modified ultrafiltration membrane substrate. The membrane thickness is only 200 nm. Moreover, the loaded COF Tp-TTA significantly increases the chemical stability and solvent resistance of the membrane, which enables a high (Chrome black T) CB-T dye rejection rate (>94%) in water and ethanol. The COF-based membrane is superior to previously reported dye-separation membranes, and has great potential.