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

Carbon dioxide capture is key to achieving carbon neutrality and addressing climate change. Covalent organic frameworks (COFs) with tailored pore structures have emerged as potential candidates for CO2 adsorption. However, previous postsynthetic modification methods often face an inevitable trade-off between increasing adsorption sites and maintaining pore accessibility. Herein, we report an all-dry molecular scale processing (MSP) approach that forms open pockets in COF mesopores by covalently grafting chains with Zn open metal sites and primary amine groups as dual CO2-philic sites. The resulting COF not only maintains a BET surface area up to 1180 m2 g-1 but also enables an ideal selectivity for CO2/N2 of 153 at 100 kPa, which is almost 10-fold higher than the pristine COF. Mechanistic investigations reveal that micropore filling and strong binding sites contribute to enhanced CO2 adsorption. The pore engineering strategy reported here provides essential insights for developing the next generation of adsorbent materials.