Combined Experimental and Computational Approaches To Elucidate the Structures of Silver Clusters inside the ZSM-5 Cavity

Abstract

A combination of experimental and computational analyses suggested the presence of Ag3 or Ag4 clusters inside a nanometer-sized cavity in Ag–ZSM-5 zeolites, which were formed from H–ZSM-5 using the conventional ion-exchange method in an aqueous silver nitrate solution. During the experimental analyses, we investigated the structural and absorption properties of Ag–ZSM-5 through UV–vis diffuse reflectance and X-ray absorption fine structure (XAFS) measurements. The results from the extended XAFS (EXAFS) analysis indicated that clusters contained in the ZSM-5 cavity have Ag–Ag separations of approximately 2.6 A. The UV–vis measurements indicated that the clusters located in the cavity present three prominent absorption bands centered at approximately 255, 287, and 331 nm for the sample treated at 473 K. The Ag–ZSM-5 treated at 573 or 673 K presents new UV–vis bands at approximately 303 and 319 nm. The experimental results regarding the structural and absorption properties of Ag–ZSM-5 could be well-reproduce...