Ab Initio and DFT Studies on CO2 Interacting with Znq+-Imidazole (q=0, 1, 2) Complexes: Prediction of Charge Transfer through σ- or π-Type Models

• Published in: Chemphyschem 2016-04, Vol.17 (7), p.994-1005
• Main Authors: Boulmene, Reda, Boussouf, Karim, Prakash, Muthuramalingam, Komiha, Najia, Al-Mogren, Muneerah M., Hochlaf, Majdi
• Format: Article
• Language: English
• Subjects: ab initio calculations; charge transfer; CO2 adsorption and selectivity; solvent effects; Zn complexes
• ISSN: 1439-4235; 1439-7641
• DOI: 10.1002/cphc.201501185

Using first‐principles methodologies, the equilibrium structures and the relative stability of CO2@[Znq+Im] (where q=0, 1, 2; Im=imidazole) complexes are studied to understand the nature of the interactions between the CO2 and Znq+–imidazole entities. These complexes are considered as prototype models mimicking the interactions of CO2 with these subunits of zeolitic imidazolate frameworks or Zn enzymes. These computations are performed using both ab initio calculations and density functional theory. Dispersion effects accounting for long‐range interactions are considered. Solvent (water) effects were also considered using a polarizable continuum model approach. Natural bond orbital, charge, frontier orbital and vibrational analyses clearly reveal the occurrence of charge transfer through covalent and noncovalent interactions. Moreover, it is found that CO2 can adsorb through more favorable π‐type stacking as well as σ‐type hydrogen‐bonding interactions. The inter‐monomer interaction potentials show a significant anisotropy that might induce CO2 orientation and site‐selectivity effects in porous materials and in active sites of Zn enzymes. Hence, this study provides valuable information about how CO2 adsorption takes place at the microscopic level within zeolitic imidazolate frameworks and biomolecules. These findings might help in understanding the role of such complexes in chemistry, biology and material science for further development of new materials and industrial applications. CO2 capture and noncovalent interactions: A study of the mechanism of CO2 adsorption at the microscopic level reveals that charge transfer and weak interactions have key roles. Charge transfer through σ‐type bonds in CO2@Znq+–imidazole (q=0, 1, 2) is dominant over π‐stacking interactions.