Ultramicroporous Covalent Organic Framework Nanosheets with Functionality Pair for Membrane C₂ H₂ /C₂ H₄ Separation

Area of Science:

• Materials Science
• Chemical Engineering
• Nanotechnology

Background:

• Covalent organic frameworks (COFs) offer tunable properties for gas separation.
• Precise functionalization of COFs is key to enhancing membrane performance.
• Achieving high selectivity and permeability simultaneously remains a challenge in gas separation technologies.

Purpose of the Study:

• To design and synthesize a pair-functionalized COF membrane for improved gas separation.
• To investigate the cooperative interaction of N-O paired groups with specific gases.
• To evaluate the performance of the developed COF membrane in separating acetylene from ethylene.

Main Methods:

• Synthesis of a pair-functionalized COF (TP-IQD) using 1,3,5-triformylphloroglucinol (TP) and isoquinoline-5,8-diamine (IQD) monomers.
• Preparation of TP-IQD nanosheets via mechanical exfoliation.
• Fabrication of a hybrid membrane by incorporating TP-IQD nanosheets into a 6FDA-ODA polymer matrix.
• Characterization of the COF structure, pore size, surface area, and gas interaction properties.

Main Results:

• The synthesized TP-IQD COF exhibits a 2D structure with a pore size of 6.5 Å and a surface area of 289 m²/g.
• The COF's N-O paired groups demonstrate selective interaction with acetylene (C2H2) over ethylene (C2H4).
• The hybrid membrane shows a 160% increase in C2H2 permeability and a 430% increase in C2H2/C2H4 selectivity compared to the pure polymer membrane.

Conclusions:

• The pair-functionality strategy is highly effective for synthesizing separation-focused COFs.
• The developed TP-IQD COF membrane exhibits superior performance for acetylene/ethylene separation.
• This work provides a promising pathway for advanced gas separation materials through rational COF design.