Fabrication of smart spherical three-dimensional covalent organic framework membranes with switchable oil–water separation via interfacial polymerization
Abstract
The three-dimensional covalent organic framework (3D COF) materials exhibit low density and facile functional group modification, rendering them highly promising for applications in adsorption, separation, and catalysis. However, there is a paucity of research on switchable oil–water separation using 3D COF materials. In this study, we have successfully fabricated a multifunctional spherical 3D COF membranes through interfacial terpolymerization. The presence of abundant hydroxyl groups within the porous structure imports hydrophilicity, while the incorporation of numerous fluorine atoms enhances lipophilicity. Furthermore, the capillary action exhibited by the spherical architecture provides an excellent foundation for pre-wetting processes. As well, by theoretical calculation, the membrane is easy to transition from the Cassie state to the Wenzel state, which is conducive to the formation of oil–water amphiphobicity membranes. By leveraging these unique characteristics, our prepared membrane enables facile transition between hydrophilic and lipophilic states via pre-wetting techniques. Moreover, it demonstrates exceptional performance in selectively separating light oil–water mixtures, heavy oil–water mixtures, water-in-oil emulsions, and oil-in-water emulsions with separation efficiencies exceeding 98?% and separation fluxes surpassing 632 L·m-2h-1bar?1. Notably, our membrane exhibits remarkable solvent stability and cyclic stability as well. We anticipate that this straightforward approach will pave the way for developing 3D COF membranes as switchable materials for efficient oil–water separation.