Understanding the Mechanisms of CO2 Adsorption Enhancement in Pure Silica Zeolites under Humid Conditions

Abstract

Using grand canonical Monte Carlo simulations, computational screening of hundreds of pure silica zeolites were conducted to identify materials that show enhanced CO2 uptake under humid conditions. Herein, we show that CO, adsorption performance can be either enhanced or degraded depending on the CO2/H2O binding site separations and characteristics of CO2/H2O interaction energies. As expected, CO2 adsorption capacity is significantly degraded when its binding sites overlap with the H2O sites. On the other hand, CO2 adsorption performance is enhanced when CO2/H2O binding sites are clearly separated as shown from the molecular simulations. However, we show that there are zeolite structures where CO2 enhancement is observed despite the close distance between the CO2 and H2O binding sites. It is demonstrated that favorable long-range Coulomb interaction between CO2 and H2O molecules is responsible for enhanced CO2 adsorption performance in these materials