Theoretical Study of NO2 Adsorption on a Transition-Metal Zeolite Model

Calculations for the study of NO2 adsorption on a transition-metal-exchanged zeolite (M=Zn, Cu, Ni, Co, Fe) were carried out using an ab initio density functional theory and pseudopotential approaches. A tritetrahedral model (T3) was used to represent the structure of the zeolite. The density functional calculations predict that the bonding energy follows the order Zn>Ni>Cu>Fe>Co. Analysis of the electronic properties shows that only in the case of Cu and Ni ions does the d10-s1d9 promotion favor interaction between the NO2 molecule and the metallic center. The optimization results show that there is a charge transfer from the metallic ion to the NO2 molecule, which produces a weakening of the N–O bond.