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NH 3 temperature-programmed desorption (NH 3 -TPD) is frequently used for probing the nature of the active sites in CuSSZ-13 zeolite for selective catalytic reduction (SCR) of NO x . Herein, we propose an interpretation of NH 3 -TPD results, which takes into account the temperature-induced dynamics of NH 3 interaction with the active centers. It is based on a comprehensive DFT/GGA + D and first-principles thermodynamic (FPT) modeling of NH 3 adsorption on single Cu-Cu] 2 species, segregated CuO nanocrystals and Brønsted acid sites (BAS). Theoretical TPD profiles are compared with the experimental data measured for samples of various Si/Al ratios and distribution of Al within the zeolite framework. Copper reduction, its relocation, followed by the intrazeolite olation/oxolation processes, which are concom-itant with NH 3 desorption, were revealed by electron paramagnetic resonance (EPR) and IR. DFT/FPT results show that the peaks in the desorption profiles cannot be assigned univocally to the particular Cu and BAS centers, since the observed low-, medium-and high-temperature desorption bands have contributions coming from several species, which dynamically change their speciation and redox states during NH 3 -TPD experiment. Thus, a rigorous interpretation of the NH 3 -TPD profiles of CuSSZ-13 in terms of the strength and concentration of the active centers of a particular type is problematic. Nonetheless, useful connections for molecular interpretation of TPD profiles can be established between the individual component peaks and the corresponding ensembles of the adsorption centers.

Cu-ZSM-5 zeolites exhibit promising NH3-SCR activity in a wide temperature window. The current challenges in preparing Cu-ZSM-5 are reducing the cost and simplifying the preparation process. The one-pot method using the Cu-amine complex as the template is an excellent strategy for solving the above problems. However, the above method is still lacking in preparing Cu-ZSM-5. In this work, a one-pot method using the Cu-(EDA)2 complex as the template is developed to prepare the Cu-ZSM-5-O catalyst. According to the fundamental measurements, the high dispersion of copper­(II) species, appropriate acidity, and Cu+ species are in favor of the NH3-SCR reaction. Among one-pot catalysts, Cu1.8-ZSM-5-O shows excellent NH3-SCR performance at low temperatures (NO conversion of about 87.5% at 150 °C and N2 selectivity above 95% over the entire temperature window). The boosting activity at low temperatures of one-pot catalysts is probably assigned to abundant [Cu­(OH)]+ species and appropriate amounts of Cu+ species in Cu-ZSM-5-O. Moreover, the variable-temperature EPR and subsequent computer simulation are used first to quantify the content of [Cu­(OH)]+ species in Cu-ZSM-5-O. The NH3-SCR mechanism at low temperatures (150 °C) on [Cu­(OH)]+ species is also investigated by in situ DRIFT spectra and DFT calculations, which mainly follow the Eley–Rideal route. A complete catalytic cycle of the SCR reaction was proposed based on the [Cu­(OH)]+ species by DFT calculations. Our results suggest that [Cu­(OH)]+ species contribute to the adsorption and activation of NH3, thus boosting the catalytic performance.

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