Abatement of dichloromethane with high selectivity over defect-rich MOF-derived Ru/TiO2 catalysts

Abstract

The regulation of oxygen vacancies and Ru species using metal–organic frameworks was synergically adopted in a rational design to upgrade Ru/TiO₂ catalysts, which are highly active for the catalytic oxidation of dichloromethane (DCM) with less undesired byproducts. In this work, Ru/M-TiO₂ and Ru/N-TiO₂ catalysts were synthesized by the pyrolysis of MIL-125 and NH₂-MIL-125 incorporated with Ru, the existence of Ru nanoclusters and nanoparticles was detected by XAFS, respectively, and the catalytic performance was analyzed comprehensively. Complete oxidation of DCM was obtained at ∼290 °C over Ru/M-TiO₂ and Ru/N-TiO₂ catalysts, while Ru/N-TiO₂ showed quite less monochloromethane (MCM) and higher CO₂ yields, and better dechlorination capacity in oxidation. The distinction comes down to that the easier desorption of chlorine could be achieved over Ru⁴⁺ which act as the main activated adsorption sites for DCM in Ru/N-TiO₂, compared to oxygen vacancies that serve as the main dissociation sites in Ru/M-TiO₂. Additionally, Ru/N-TiO₂ exhibited superior stability and excellent resilience in moisture. An in situ DRIFTS experiment further indicated the different DCM catalytic degradation process as well as the reaction mechanism over the as-prepared catalysts.