Copper Pairing in the Mordenite Framework as a Function of the CuI/CuII Speciation

A series of gas-phase reactants is used to treat a Cu-exchanged mordenite zeolite with the aim of studying the influence of the reaction environment on the formation of Cu pairs. The rearrangement of Cu ions to form multimeric sites as a function of their oxidation state was probed by X-ray absorption spectroscopy (XAS) and also by applying advanced analysis through wavelet transform, a method able to specifically locate Cu-Cu interactions also in the presence of overlapping contributions from other scattering paths. The nature of the Cu-oxo species formed upon oxidation was further crosschecked by DFT-assisted fitting of the EXAFS data and by resonant Raman spectroscopy. Altogether, the Cu-I/Cu-II speciation clearly correlates with Cu proximity, with metal ion pairs quantitatively forming under an oxidative environment.

Automated summary

In this study, a series of gas-phase reactants were used to investigate the formation of Cu pairs in a Cu-exchanged mordenite zeolite under different reaction environments. The rearrangement of Cu ions to form multimeric sites was studied using X-ray absorption spectroscopy and advanced analysis through wavelet transform. The results showed that under an oxidative environment, Cu-I/Cu-II speciation correlated with Cu proximity, with metal ion pairs quantitatively forming.