Electronic Structure Modulation in Covalent Organic Frameworks through Ethynyl Positioning for Enhanced...

Area of Science:

• Materials Science
• Adsorption Science
• Environmental Chemistry

Background:

• Iodine capture from industrial emissions is challenging.
• Covalent organic frameworks (COFs) with ethynyl groups show promise for iodine adsorption.
• The positioning of ethynyl groups (embedded vs. pendant) in COFs impacts performance.

Purpose of the Study:

• To investigate the effect of ethynyl group positioning in COFs on iodine adsorption.
• To synthesize and characterize framework-embedded ethynyl-COF (TPEB-TAPB-COF), pore-pendant ethynyl-COF (BPO-TAPB-COF), and a non-ethynyl COF (TFPB-TAPB-COF).
• To evaluate iodine capture performance under saturated vapor and simulated industrial conditions.

Main Methods:

• Synthesis of three distinct COFs with varying ethynyl group configurations.
• Iodine adsorption capacity measurement under saturated iodine vapor.
• Iodine adsorption testing under simulated industrial conditions (150 °C, 150 ppmv I2).

Main Results:

• TPEB-TAPB-COF (framework-embedded) achieved a high iodine capture capacity of 8.65 g/g under saturated conditions.
• Pore-pendant ethynyl groups in BPO-TAPB-COF showed reduced capacity due to limited electron delocalization.
• TPEB-TAPB-COF exhibited excellent performance (0.493 g/g) under simulated industrial conditions, outperforming most porous materials.

Conclusions:

• Framework-embedded ethynyl groups enhance electron delocalization, leading to superior iodine adsorption in COFs.
• The positioning of ethynyl groups is critical for optimizing COF performance in iodine capture.
• This study presents a new design strategy for developing advanced radioactive iodine capture materials.