Structural and Photophysical Characterization of AgClusters in LTA Zeolites

Ag clusters (AgCLs) confined within Na-exchanged Linde type A zeolites are studied by X-ray absorption and steady-state and time-resolved photoluminescence spectroscopies in a coordinated effort to elucidate the photophysical properties and link them to the precise cluster structure. The hydrated sodalite cage contains mostly tetrahedral [Ag4(H2O)4] clusters located at the center of the sodalite cages, whereas octahedral Ag6 clusters coordinated with the zeolite framework oxygen (OF) [Ag6(OF)14] are formed upon dehydration. The time-dependent density functional theory and electron spin resonance reports suggest that both Ag4 and Ag6 clusters have formally a double positive charge of 2+. Time-resolved spectroscopy shows that at room temperature, the emission of the hydrated sample decays with 3.4 ns from a state with the same multiplicity as the ground state. Upon dehydration, the entire excited-state dynamics speeds up to 1.2 ps. The microsecond-scale lifetimes observed at 77 K suggest the occurrence of t...