Functionalized Covalent Organic Framework: Boosting CO₂ Adsorption via Porous Structure Engineering and Molecular Interactions

As porous crystalline materials, covalent organic frameworks, containing an abundant porous structure, can be adopted as host materials for gas adsorption. A series of functionalized covalent organic framework materials, including methoxy-modified COF-A-OMe and vinyl-modified COF-A-Vinyl, have been constructed to compare with original COF-A in terms of regulation of topology and thermal stability. Upon application for CO₂ adsorption, improved adsorption properties have been achieved for COF-A-OMe and COF-A-Vinyl materials with functional group modification. This can be ascribed to the large specific surface area and enhanced pore volume of modified COF materials as well as the optimized adsorption advantages based on the interaction between modified functional groups and CO₂ molecules. Although a physically dominated adsorption mechanism existed for COF-A, COF-A-OMe, and COF-A-Vinyl, the synergistic role of -C═N- and -CH═CH₂ groups in COF-A-Vinyl for CO₂ adsorption has been confirmed based on density functional theory (DFT) simulation. This work can extend the application of organic frameworks for gas adsorption with a rational structure design or functional modification.