Theoretical study of the microscopic appearance of the capture and storage of CO₂ by zeolites: Studies of Zn-imidazole and triazole clusters with CO₂

Several experimental and theoretical studies have shown the ability of zeolitic-imidazole frameworks (ZIFs) materials to capture the CO₂ gas. In this study, we have focused on the interaction of CO₂ with one of the sub-unit of ZIFs i.e. the complex between the imidazole and zinc (Im-Zn+q, q = 0,1, 2) or triazole without zinc. Various adsorption sites are examined for these complexes.The calculations were performed using ab initio methods MP2; CCSD(T)-F12 and density functional theory with PBE PBE0, M1 and M05-2X functionals with different basis set (aug-cc-pVDZ, aug-cc-pVTZ and 6-311++G(d, p), tightly integrated in GAUSSIAN and MOLPRO packages. The Grimme corrections for dispersion forces description (DFT-D3) are also included. Our results shows that the stability of our complex structures is achieved by the presence of strong covalent bonds (chemical bonds of organic ligands) and also by Van der Waals and hydrogen weak bonds. Both types of bonding are in competition. This allowed us to better understand the experimental observations. (author)