The identification and quantification of multinuclear Cu-oxo cations in Cu-zeolites is a challenge amidst the dynamic nature of Cu ions in Cu-zeolites. Herein, we synthesized Cu-SSZ-13 zeolites containing varying densities of monomeric Cu cations (Z<sub>2</sub>Cu and ZCuOH, where Z represents an anionic site on the <u>z</u>eolite framework). The number of Cu-oxo cations, quantified using carbon monoxide temperature programmed reduction (CO-TPR), quadratically increased with increasing ZCuOH density, evidencing that proximal ZCuOH sites are precursors to Cu-oxo dimers. We also find that dehydrated proximal ZCuOH with overlapping diffusion radii of at most 0.5 nm can form Cu-oxo dimers. CO-TPR also revealed the presence of three distinct pools of Cu-oxo dimers; these pools catalyze dry NO oxidation at different turnover rates, with the fastest pool 2 to 30 times faster than the slowest pool. Although the precise structural and electronic nature of these pools of Cu-oxo species are still unclear, it begs to question how these pools impact other oxidation chemistries such as methane upgrading (to methanol, dimethyl ether, etc.), CO oxidation, the partial oxidation of aromatics, among others. This fundamental understanding of site requirements will aid in devising strategies for more efficient catalysts.

Multinuclear copper active sites for dry NO oxidation over Cu-SSZ-13

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