Insight into the role of Na distribution in Cu-SSZ-39 catalysts

• Na + cations predominantly occupied the 6MR sites of SSZ-39 zeolites . • Na locations in Cu-SSZ-39 zeolites affected Cu distribution. • Cu-SSZ-39 obtained directly by Na-SSZ-39 exhibited higher deNO x efficiency. • Na locations did not alter the reaction mechanism of Cu-SSZ-39 at low temperature. Cu-SSZ-39 has garnered significant attention because of its outstanding NH 3 -SCR activity and hydrothermal stability. To facilitate commercial application of Cu-SSZ-39, it is crucial to streamline the synthesis process, adopt eco-friendly synthesis methods, enhance the catalytic performance, and explore the underlying catalytic mechanisms. Herein, ammonia exchange was skipped and Cu-SSZ-39 was directly synthesized via Cu-exchange of Na-SSZ-39. This approach yielded a Cu-SSZ-39 with superior catalytic performance compared to that prepared using the conventional NH 4 -SSZ-39. Comparative characterization of the Cu-SSZ-39 catalysts, derived from both Na-SSZ-39 and NH 4 -SSZ-39 exchanges demonstrated that the positioning of Na cations affected Cu distribution, and controlling Na distribution can enhance deNO x activity. It was also found that while cation locations did not alter the reaction mechanism of Cu-SSZ-39 at low temperature, they did increase the concentration of active NO x intermediates, thereby boosting catalytic performance. This study facilitates a more sustainable synthesis of Cu-SSZ-39 and provides deeper insights into how cations’ distribution in zeolites affects catalytic efficiency.