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

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 CO₂ 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.