Chemometric analysis of diffuse reflectance spectra of Co2+-exchanged zeolites: spectroscopic fingerprinting of coordination environments

A new method for spectroscopic fingerprinting of the coordination environments of Co2+ in zeolites is proposed and discussed. The method is based on the application of different chemometric techniques (curve fitting, Principal Component Analysis (PCA) and SIMPLe-to-use Interactive Self-Modeling Analysis (SIMPLISMA)) on a series of diffuse reflectance (DR) spectra of Co2+-exchanged zeolites dehydrated at 400 °C and 500 °C. Two Co2+ species were determined for CoA and assigned to trigonal and pseudo-tetrahedral coordination of Co2+ at the hexagonal windows of six oxygens. Three components were determined for CoX and CoY: two of them are similar to those of zeolite A; the third one is ascribed to pseudo-octahedral Co2+ in the hexagonal prisms.