A density functional theory study of C–H bond activation of methane on a bridge site of M–O–M-ZSM-5 Clusters (M = Au, Ag, Fe and Cu)

Abstract

C–H bond activation of methane on a bridge site M–O–M- of ZSM-5 (M = Au, Ag, Fe and Cu) clusters has been performed by means of Density Functional Theory (DFT) calculations with the utilization of [Si 6Al 2O 9H 14(M–O–M)] 2+ (where M = Au, Ag, Fe and Cu) cluster models representing ZSM-5 surfaces. According to the activation barrier data based on TS calculations. The following activity order of clusters with respect to their activation barriers could be classified: Ag ≈ Au > Cu » Fe for Metal–O–Metal-ZSM-5 clusters. Activation barriers for C–H bond activation of methane on Au–O–Au- and Ag–O–Ag-ZSM-5 clusters are calculated as 4.83 and 4.79 kcal/mol, respectively. These values are lower than the activation barrier values for C–H bond activation on Cu–O–Cu-ZSM-5 and Fe–O–Fe-ZSM-5 which are 9.69 and 26.30 kcal/mol, respectively. Activation process is exothermic on Au–O–Au-, Cu–O–Cu-, and Fe–O–Fe-ZSM-5 clusters whereas it is endothermic on Ag–O–Ag-ZSM-5 cluster.