Understanding the Effect of Trace Amount of Water on CO2 Capture in Natural Gas Upgrading in Metal-Organic Frameworks: A Molecular Simulation Study

In this work, molecular simulations were performed to investigate the effect of trace amount of water on CO2 capture in natural gas upgrading process in a diverse collection of 25 metal-organic frameworks (MOFs). The results show that the interaction between water molecules and MOFs plays a crucial role: at the condition of weak interaction, water molecules move freely in the materials and show a negligible effect on the adsorption selectivity of CO2/CH4; while when the interaction is strong enough that water molecules are adsorbed to the preferential adsorption sites in MOFs, the effect can be significant, depending on the strength of water adsorption. In this case, the electrostatic interaction produced by the MOF framework is the dominant factor. This work provides a better understanding of the different behaviors of water effect on CO2 capture observed previously that may guide the future application of MOFs in industrial separations.