Quantification of Exchanged Copper Species in Cu‐Chabazite Zeolite using Cryogenic Probe Infrared Spectroscopy

The development of a low temperature (−160 °C) NO adsorption technique is disclosed that avoids the chemical conversion of the probe molecule at room temperature. The observed IR peaks for Cu+(NO)2 and Cu2+(NO) species can be used to quantify the amount of exchanged copper species in a broad range of samples, including a wash‐coated honeycomb. Calibration curves for Cu+(NO)2 and Cu2+(NO) are determined for copper loadings up to 3.99 wt% with Silica‐to‐Alumina Ratio (SAR) of 16–22, and quantitative agreement with the complementary hydrogen Temperature Programmed Reduction (H2‐TPR) results is established. This methodology allows to identify different Cu species in Cu‐CHA, such as Z2Cu(II), Z1Cu(II)OH and Cu dimers, based on their distinct IR signatures. In addition, the perturbed T−O−T framework vibration – characterized at 400 °C – can also be used as a complimentary method to quantify Z2Cu(II) species. Copper quantification: This work demonstrates that cryogenic NO‐IR is a facile technique to identify and quantify the exchanged copper species in Cu‐CHA. The observed IR peaks for Cu+(NO)2 and Cu2+(NO) species can be used to quantify the amount of exchanged copper species in a broad range of samples, including a wash‐coated honeycomb.