Water Effects on Postcombustion CO2 Capture in Mg-MOF-74

Mg-MOF-74, one of the best metal–organic framework (MOF) materials for CO2 adsorption and separation, has been widely explored in CO2 capture. In this work, water effects on postcombustion CO2 capture in Mg-MOF-74 are evaluated by using a combination of Grand Canonical Monte Carlo and density functional theory (DFT) simulations. Our results show that in this MOF the CO2 adsorption capacity is decreased by the presence of water molecules linked to coordinatively unsaturated metal sites (CUMs). This effect is a consequence of the reduction of binding energy between CO2 and the water-coordinated Mg-MOF-74 framework. DFT calculations indicate that such binding energy is much lower than that without coordinated water. More importantly, we find that the difference of the binding energy between CO2 and CUM in a MOF and that between CO2 and CUM-coordinated water are good descriptors to evaluate water effects on CO2 capture in MOFs with CUMs. At the same time, these investigations further demonstrate that the CUMs in MOFs play an important role in their performance for CO2 capture from a practical stream containing water and other impurities.