Siting of the Cu + ions in dehydrated ion exchanged synthetic and natural chabasites: a Cu + photoluminescence study

Abstract

Cu + emission spectra of Cu 2+ ion exchanged and reduced natural and synthetic CuNa-, CuCa-, CuCs- and CuBa-chabasites were used to identify cationic sites of the Cu + luminescence centres in this zeolite. Two different Cu + emission bands with maxima at 500 and 540 nm were observed; the emission at 540 nm prevailed at higher Cu loadings. The concentration dependence of the intensity of 500 and 540 nm emission bands indicated that both bands correspond to the single Cu + ions. The effect of the presence of co-cations in Cu-chabasites on the luminescence spectra was employed for the identification of the cationic sites corresponding to the individual emission bands. Cu + emission at 500 nm reflects the Cu + ion located at the cationic site in the eight-membered ring. Cu + emission at 540 nm is attributed to the Cu + ion coordinated to three oxygen atoms of the regular six-membered ring. The Cu + ion in this site is suggested to be located above the six-ring plane, similar to the siting of Cu + ions in Y zeolite.