A promising metal-organic framework (MOF), MIL-96(Al), for CO2 separation under humid conditions

The CO2 adsorption uptake and enthalpies with MIL-96(Al) were assessed in the presence of up to 40% relative humidity via both experiment and simulation. Interestingly at 10% relative humidity, the water equilibrated in the pores of this MOF proffers a significant increase in affinity for CO2 at 0.2 bar, which is associated with a limited decrease in capacity. This study suggests that at medium RH, water and CO2 are able to adsorb in different regions of the structure. Indeed, such behaviour is explained by the preferential adsorption of H2O in cavities containing more hydrophilic groups including Al(1)-H2Oterminal, Al(3')-OHterminal and Al(3)-H(2)Oterminal while CO2 adsorbs in the remaining, less hydrophilic cavities containing mu(2)-OH groups. This highlights the interest of using materials with this variety in pore chemistry as one way forward for CO2 capture in the presence of contaminants such as water.