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 (Cu_6mr···O_4mr) 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.