All-Dry Molecular Scale Processing for Shaping Open Pockets with CO₂ Affinity in a Covalent Organic Framework

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Carbon dioxide capture is crucial for climate change mitigation and achieving carbon neutrality.
• Covalent organic frameworks (COFs) show promise for CO2 adsorption due to their tunable structures.
• Existing modification methods for COFs often compromise pore accessibility while increasing adsorption sites.

Purpose of the Study:

• To develop an efficient method for enhancing COF performance in CO2 capture.
• To engineer COF pore structures for improved CO2 adsorption capacity and selectivity.
• To overcome the trade-off between adsorption sites and pore accessibility in modified COFs.

Main Methods:

• An all-dry molecular scale processing (MSP) approach was employed.
• Chains with Zn open metal sites and primary amine groups were covalently grafted into COF mesopores.
• The modified COFs were characterized for surface area, pore structure, and CO2/N2 selectivity.

Main Results:

• The MSP approach created open pockets within COF mesopores.
• The modified COF retained a high BET surface area (1180 m2 g-1).
• An exceptional CO2/N2 selectivity of 153 at 100 kPa was achieved, a nearly 10-fold increase over the pristine COF.

Conclusions:

• The developed pore engineering strategy significantly enhances CO2 adsorption.
• Micropore filling and strong binding interactions are key mechanisms for improved adsorption.
• This method offers a promising pathway for designing advanced adsorbent materials for CO2 capture.