Reduction of NO to N2O Catalyzed by a Mn-Substituted Keggin-Type Polyoxometalate: A Density Functional Theory Study

Abstract

Reaction mechanism corresponding to reduction of NO to N2O catalyzed by mono-transition-metal-substituted Keggin-type polyoxometalates (POMs) has been studied by using a density functional theory (DFT) method with the M06L functional. Compared with Fe-, Co-, and Zn-substituted POM complexes, a Mn-substituted POM complex possesses good feature for activation of NO molecule because of considerable absorption energy and significant charge transfer from metal center to NO molecule. The effective interaction between NO ligand and the Mn center mainly comes from an overlap of the π* orbital of the NO molecule with dxz and dz2 orbital of Mn center. Three possible reaction pathways for reduction of NO to N2O catalyzed by Mn-substituted POM complex have been considered based on a dimer mechanism. The calculated free energy profile indicates that the reaction pathway undergoing a cis-(NO)2 conformation is the favorable route because of a low free energy barrier of 4.24 kcal mol–1. This work would be very useful to ...