XAFS study of silver clusters in zeolites.
The EXAFS measurements on Ag K-edge have been carried out at 298K on completely Ag+-exchanged zeolite 4A(Ag-4A) with different dehydration treatments. Ill the Fourier trmislbnns F(r) of EXAFS spectra there appear two distinct peaks. By two-shell curve-fitting analysis it is tbund that the Ag ion-ti-amework oxygen and Ag-Ag contact distances decrease as the color of Ag4A changes fi-om white (fidly hydrated) to brown (fitlly dehydrated). The coordination number of Ag atom (Ag °) around a central Ag °, 9.0 + 0.5, tbr brown Ag-.4A suggests a tbnnation of a silver cluster with Ag o -Ag o contact distance of 2.81 A.