Theoretical Study of the CO2 Adsorption by Zeolitic Imidazolate Frameworks (ZIFs)

Density functional theory with Grimme's empirical correction, DFT-D3, has been used to examine the adsorption of a carbon dioxide molecule by different sets of zeolitic imidazolate framework materials (ZIF-1 to -4, -6 to -10, and -zni). We have calculated the interaction energy, the dipole moment variation, and the charge density difference for the different CO2@ZIF structures. Our study shows a strong relationship between the CO, adsorption energy and the volume of the cavities of the ZIFs: the capture of carbon dioxide depends on the shape and size of the ZIFs pore in which CO, has been inserted. The physisorption phenomena that govern the adsorption of CO, molecule require both it-stacking interactions and hydrogen-like bonding. We have found that adsorption does not change the geometry of CO2, but it induces a significant structural change in some ZIF structures.