Tunable Wettability of a Dual-Faced Covalent Organic Framework Membrane for Enhanced Water Filtration

Membrane technology plays a central role in advancing
separation
processes, particularly in water treatment. Covalent organic frameworks
(COFs) have transformative potential in this field due to their adjustable
structures and robustness. However, conventional COF membrane synthesis
methods are often associated with challenges, such as time-consuming
processes and limited control over surface properties. Our study demonstrates
a rapid, microwave-assisted method to synthesize self-standing COF
membranes within minutes. This approach allows control over the wettability
of the surface and achieves superhydrophilic and near-hydrophobic
properties. A thorough characterization of the membrane allows a detailed
analysis of the membrane properties and the difference in wettability
between its two faces. Microwave activation accelerates the self-assembly
of the COF nanosheets, whereby the thickness of the membrane can be
controlled by adjusting the time of the reaction. The superhydrophilic
vapor side of the membrane results from −NH2 reactions
with acetic acid, while the nearly hydrophobic dioxane side has terminal
aldehyde groups. Leveraging the superhydrophilic face, water filtration
at high water flux, complete oil removal, increased rejection with
anionic dye size, and resistance to organic fouling were achieved.
The TTA-DFP-COF membrane opens new avenues for research to address
the urgent need for water purification, distinguished by its synthesis
speed, simplicity, and superior separation capabilities.