Theoretical Study of Pyrrole Interaction with Alkali Metal Exchanged Zeolites: Investigation of the Reliability of Cluster and Periodic Models

Abstract

The interaction of pyrrole with the alkali metal exchanged zeolites was investigated using cluster models of various sizes and with a hybrid quantum mechanics/interatomic potential function model (QM-pot). The interaction of pyrrole with the M+/zeolite is dominantly driven by the interaction of pyrrole π-system with the alkali metal cation. Further stabilization is due to the formation of the hydrogen bonds between NH and framework oxygen atoms. A good agreement between calculated and experimental shift of the N-H stretching vibration upon the adsorption of pyrrole in M+/zeolite was found with the periodic QM-pot model. The performance of the cluster models for the description of pyrrole interaction with M+/zeolite is discussed. Reliable results can be obtained only when large cluster models are used for description of the zeolite framework.