Activation of NO2 by Modifying the Porphyrin Unit with Oxygen in a MnN4 Graphene Layer

Abstract

AbstractIn this article, the activation of N−O bonds in NO2 molecules has been investigated by Density Functional Theory (DFT) calculations. Considering the graphene‐based MnN4 layer, nitrogen atoms in the porphyrin unit were sequentially replaced with oxygen atoms to create different MnNmOn/G (m+n=4 and 1<m≤4) layers. As more oxygen atoms are incorporated in porphyrin units for bare layers, the covalent character of the Mn−O bonds is switched to the transit nature with respect to Mn−N bonds. Moreover, the trend in bond strength decreasing in all oxygen‐containing bonds is in line with the formation energy trends of bare layers. The same situation is also valid for the bonds between Mn−N/O. For NO2 adsorption configurations on all MnNmOn/G layers, N−O bonds in NO2 are weakened by populating/depopulating antibonding/bonding orbitals, respectively. Even if the MnN2O2(hex)/G layer has a moderate NO2 adsorption energy among the other layers, this layer provided the most significant activation over N−O bonds based on crystal orbital Hamilton population (COHP), crystal orbital bond index (COBI), and Atoms in Molecules (AIM) Bader Topological Analysis. Our results show that integrated COHP and integrated COBI values show a remarkable correlation with AIM‐Bader parameters for the specific bonds which have descriptive capability over NO2 molecule activation.