Energetics and Structure of Ag-Water Clusters Formed in Mordenite

Zeolite-supported Ag⁰ clusters have broad applications from catalysis to medicine, necessitating a mechanistic understanding of the formation of Ag⁰ clusters in situ. Density functional theory (DFT) simulations have been performed on silver, water, and silver-water clusters in silica mordenite (Si-MOR), to identify the role of the confinement on the structure and energetics of Ag⁰ cluster formation. The most favorable binding energy in the 12-membered ring (MR) pore of the Si-MOR is a 10-15-atom Ag⁰ cluster. Computational pair distribution function (PDF) data indicates that the Ag⁰ and Ag⁰-H₂O clusters formed in vacuum versus in Si-MOR exhibit structural differences. Additionally, when the Ag⁰ cluster is confined, the density decreases and the surface area increases, hypothesized to be due to the limiting geometry of the 12-MR main channel. An energetic drive toward formation of larger Ag⁰ clusters was also identified, with hydrated silver atoms generating higher energy structures. Overall, this work identifies mechanistic and structural insight into the role of nanoconfinement on formation of Ag⁰ clusters in mordenite.