Linkage engineering of covalent-organic frameworks for CO2 capture

The growing concern over climate change due to the continuous increase in CO2 concentration calls for efficient ways for carbon capture. Covalent-organic frameworks (COFs), as a new type of porous materials, are considered ideal platforms for carbon capture due to their high surface area and porosity, while their intrinsic CO2 uptake is relatively low owing to the lack of functionalities. Herein, we report a linkage engineering strategy to develop more efficient CO2 adsorbents through the conversion of imine-bonded COFs to amide-bonded COFs. After conversion, the CO2 uptake capacity is increased significantly from ∼ 55 mg/g to ∼ 235 mg/g, while the N2 uptake capacity remains almost unchanged, and breakthrough experiments show that the CO2/N2 separation performance is greatly improved. Monte Carlo simulations and density-functional theory calculations show that the interaction between the carbonyl group in the amide segment and the CO2 molecule is the key to the improved performance. Overall, this work provides an efficient and facile strategy for the structural design of COFs for carbon capture applications.