The sorption and separation mechanism of CO2 in covalent organic frameworks with different aligned structures: DFT and molecular dynamic simulations

Insight into the sorption and separation mechanism of CO2 in covalent organic frameworks (COFs) is vital for efficient CO2 capture and separation. It is noted that COFs with amine functional groups facilitates CO2 sorption compared with the other COFs. Firstly, COFs with hydrazone-based functional groups as an example is used to analyze the interactions of CO2 with hydrazone-based COFs (N-COFs) and the effect of stacking pattern (AA and AB staking) on CO2 sorption and separation property in different mixed gases by DFT and molecular dynamic simulation. Secondly, the CO2 separation effects of N-COFs with different layer spacing and pore size were compared. The results showed that the stronger interaction of CO2 with N-COFs result in higher sorption capacity of CO2 compared with that of the other gas, which facilitate the storage and separation of CO2. Moreover, the stacking pattern of N-COFs result in the different migration path of gases, and the CO2 separation effect of N-COFs are improved by adjusting its layer spacing and pore size. In conclusion, the separation of N-COFs for CO2 is affected by the combined action of CO2 adsorption energy, the species of the mixed gas and the size sieving effect.