Enhanced CO 2 adsorption in metal-organic frameworks via occupation of open-metal sites by coordinated water molecules

Abstract

CO 2 is one of the most important greenhouse gases and its removal from flue gas and natural gas has become increasingly important. We report an interesting discovery in which the CO 2 uptake and its selectivity over N 2 and CH 4 in the metal-organic framework (MOF) Cu-BTC were significantly increased by the presence of water molecules coordinated to open-metal sites in the framework. This was first predicted by molecular simulations and later validated by experiments. A detailed analysis of simulation data revealed that interaction between the quadrupole moment of CO 2 and the electric field created by water molecules is responsible for the enhanced CO 2 uptake. These findings could open new possibilities for tuning the adsorption behavior of MOFs for CO 2 capture and other applications. © 2009 American Chemical Society.