The quantity of Cu+ ions forming isolated and bridged carbonyl complexes in FER zeolites determined by IR spectroscopy

The integral absorption coefficients for IR bands of carbonyl complexes formed in Cu+Me+-FER zeolites (Me = Na, K, Cs) were determined. Previous work on such systems based on combination of several experimental techniques and perDFT calculations showed that stable monodentate carbonyls on isolated cations in the so-called single cation sites (SCS) Cu+-CO and Cu+-CO-Me+ (Me = K, Cs) complexes, where CO molecule is bridging two nearby cations in the so-called heterogeneous dual cation sites (DCS), are formed. In this contribution we made an attempt to determine the quantity of individual carbonyl types using the analysis of IR spectra for CO monolayer coverage on Cu+Me+-FER samples varying in copper content, type of co-cation and nominal Si/Al ratio. Study results in conclusion that IR absorption for SCS (band at 2156 cm−1) and heterogeneous DCS (bands at 2138 and 2112 cm−1) complexes has the same magnitude and reaches 21.5 cm μmol−1. The 95% confidence limits were estimated at ±7%. The quantity determination of monovalent copper forming two kinds of carbonyl species in FER pentasil zeolites is demonstrated.