Ion-Exchanged Cu-SSZ-13 for Catalytic Removal of Dichloromethane: The Essence of Isolated Cu Cations and Reaction Mechanism.

An ion-exchanged Cu-SSZ-13 catalyst exhibited excellent performance in the deep oxidation of dichloromethane, achieving a high reaction rate of 2.41 mmol g-1 h-1 at 200 °C without producing chlorine-containing byproducts. Detailed characterizations indicated abundant isolated Cu species, specifically, [ZCu2+(OH)]+ and Z2Cu2+, in the catalyst. Quantitative analysis of the activity results demonstrated that the Z2Cu2+ in a 6-membered ring had the highest activity (with a turnover frequency of 1.8 × 10-3 s-1 at 200 °C), which was 5-fold higher than that of the [ZCu2+(OH)]+ species in an 8-membered ring and 9-fold higher than the acid sites in the SSZ-13 support. Importantly, the isolated Cu species remained intact during the reaction, ensuring good catalyst stability. In contrast, CuO particles, present in a higher amount in an impregnated Cu/SSZ-13 catalyst, were readily chlorinated, leading to notable deactivation. Moreover, theoretical calculations unraveled the reaction routes, clarifying the crucial role of the frustrated Lewis pair (Cu6mr···O4mr) species in accelerating the reaction. Therefore, this study not only broadens the application scope of SSZ-13-based catalysts but also provides valuable insights for designing efficient catalysts for the catalytic removal of chlorinated volatile organic compounds.