Ultrathin zwitterionic COF membranes from colloidal 2D-COF towards precise molecular sieving

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Membrane technology is crucial for resource recovery in industrial processes.
• Covalent organic frameworks (COFs) possess ordered structures and porosity, making them suitable for advanced membrane fabrication.
• Zwitterionic COFs offer unique properties compared to single ionic COFs.

Purpose of the Study:

• To synthesize a zwitterionic colloidal 2D-COF (TpPa-Py) and fabricate ultrathin membranes.
• To evaluate the performance of these zwitterionic COF membranes for dye and salt separation.
• To explore the potential of these membranes for resource recovery from dye wastewater.

Main Methods:

• Single-phase synthesis of zwitterionic colloidal 2D-COF (TpPa-Py).
• Facile blade-coating method for fabricating ultrathin zwitterionic COF membranes.
• Experimental characterization and molecular dynamics simulations to assess membrane performance.

Main Results:

• The zwitterionic TpPa-Py membrane demonstrated high permeance and rejection for both positively and negatively charged dyes.
• Excellent separation performance was achieved for dye/dye mixtures (selectivity factor of 89 for Acid Blue/Rhodamine B) and dye/salt mixtures (selectivity factor of 47.8 for Methyl Blue/NaCl).
• The amphiphilic nature of TpPa-Py contributes to its separation capabilities.

Conclusions:

• Zwitterionic COF membranes provide a promising solution for high-performance separation in dye wastewater treatment.
• The developed membranes are effective for resource recovery and address critical needs in water treatment.
• This work highlights the potential of tailored zwitterionic COFs for advanced membrane applications.