In-Situ XAFS, Photoluminescence, and IR Investigations of Copper Ions Included within Various Kinds of Zeolites. Structure of Cu(I) Ions and Their Interaction with CO Molecules

Abstract

The characterization of the coordination geometry of copper ions included within zeolites has been carried out with a combination of in-situ XAFS, photoluminescence, and IR measurements in order to obtain a detailed description of the formation of isolated Cu + monomers with planar 3-coordinate or linear 2-coordinate geometry in the zeolite channels by thermal treatment under vacuum. The Cu + ions within the zeolites were found to exist as isolated Cu + monomers and (Cu + −Cu + ) dimers, their relative concentrations strongly depending on the type of zeolite used. With ZSM-5 and mordenite zeolites, most of the copper cations were found to exist as isolated Cu + monomers, in contrast to the case of the Y-zeolite. CO molecules were adsorbed selectively only on isolated Cu + monomers, distorting the coordination geometry to form stable one-on-one Cu + −CO complexes.