Highly efficient light-gated COF membrane for precise multistage molecular separation.

Area of Science:

• Materials Science
• Chemical Engineering
• Nanotechnology

Background:

• Membrane technology is vital for chemical and biochemical separations, but conventional methods are inefficient and energy-intensive.
• Multistage separations typically require multiple membranes with varying pore sizes, limiting efficiency.
• Natural stomata offer a model for responsive and efficient separation processes.

Purpose of the Study:

• To engineer a light-gated covalent organic framework (COF) membrane with dynamically tunable pore sizes.
• To demonstrate the membrane's capability for efficient multistage separations of valuable compounds and ions.
• To provide a novel strategy for developing advanced separation membranes.

Main Methods:

• Fabrication of a COF membrane incorporating 53.5 wt% azobenzene using click chemistry.
• Utilizing the reversible trans-cis isomerization of azobenzene to dynamically switch pore size between 0.73 and 0.93 nm.
• Testing the membrane for multistage separations of hemp oil components (cannabidiol oil, limonene, chlorophyll) and metal ions (gold, silver, iron).

Main Results:

• The light-gated COF membrane successfully achieved precise multistage separations of high-value pharmaceutical compounds and metal ions.
• The membrane's pore size was dynamically controlled by light, switching between 0.73 and 0.93 nm.
• The separation process demonstrated excellent stability over 100 cycles due to robust triazole bond formation.

Conclusions:

• The developed light-gated COF membrane offers a highly efficient and flexible alternative to conventional separation techniques.
• This technology enables precise molecular separations applicable to pharmaceuticals and resource recovery.
• The study presents an instructive strategy for designing responsive COF membranes for advanced applications.