Rapid fabrication of fluorinated covalent organic polymer membranes for organic solvent nanofiltration

Covalent organic polymers (COPs) are prepared via the non-uniform covalent assembly of organic building blocks, endowing their structures with permanent pores, thereby rendering them suitable for diverse applications. The use of COPs in the fabrication of composite membranes can enhance their permeability, selectivity, and chemical stability. However, the existing COP synthesis processes are typically tedious, thus necessitating the development of rapid and simpler routes. We demonstrate an easily performed synthesis route for the rapid (less than 10 s) fabrication of COP-based composite membranes via interfacial polymerization. The membranes were directly prepared on a polyacrylonitrile substrate without transferring the COP layer onto a porous support. The hydrophobicity of the membranes was achieved by the integration of fluorine-rich groups along the polymer backbone. The obtained solvent-resistant composite membranes exhibited a toluene permeance of 11 L m⁻² h⁻¹ bar⁻¹ and congo red (687 g mol⁻¹) rejection levels of more than 95%. The remarkable performance, crosslinked polymer structure, and manufacturing scalability of the fabricated thin films make them attractive as solvent-resistant nanofiltration membranes.