Effects of water vapor and trace gas impurities in flue gas on CO2 capture in zeolitic imidazolate frameworks: The significant role of functional groups

The water vapor and trace gas impurities play important roles on CO2 capture performance using porous materials. We investigated the effects of H2O, SO2, and O2 on CO2 capture in a series of ZIFs with same SOD topology but different functional groups, such as ZIF-8, ZIF-90, ZIF-Cl, ZIF-NO2, and SALEM-2 by grand canonical Monte Carlo simulations. The results show that H2O and SO2 show a cooperative effect on CO2 adsorption in ZIF-NO2 and ZIF-90 containing polar functional groups, which results in enhanced CO2/N2 selectivity in presence of H2O or SO2. Especially, the presence of H2O or SO2 can enhance the CO2 uptake amounts and the CO2/N2 selectivity in ZIF-NO2 at all H2O or SO2 concentration. On the other hand, the presence of H2O, SO2 has negligible effect on CO2 adsorption and CO2/N2 separation in ZIF-8, ZIF-Cl, and SALEM-2. The presence of O2 has no effect on CO2 capture in all of the materials investigated. Our results indicate that, by changing the functionalities of ZIF materials, H2O and SO2 may play a positive role during CO2 adsorption and separation process.