Accelerating chlorine desorption from metal active sites in thermal catalytic oxidation of dichloromethane via UV-vis assistance for persistent and complete mineralization

Abstract

Thermal catalytic oxidation has achieved widespread industrial adoption for eliminating chlorinated volatile organic compounds, yet it remains persistently restricted by chlorine poisoning of metal active sites, resulting in reduced efficiency and stability and increased by-product formation. To address this challenge, we developed a Pt nanoparticle-loaded TiO₂ catalyst (PCTO) derived from a metal organic framework, in which introducing UV-vis irradiation into the thermal catalytic oxidation process promotes chlorine desorption from the metal active sites, thereby enabling the efficient and stable degradation of dichloromethane (DCM). The optimal PCTO-3 shows exceptional photothermal catalytic performance with ≥99% DCM conversion and mineralization rates under UV-vis irradiation at 275 °C, far surpassing that of the MOF-derived TiO₂ catalyst (CTO). Remarkably, this outstanding activity is well maintained even when the catalytic time is prolonged to 9 h and when 2 vol% water vapour is present for over 10 h. In situ XPS and in situ DRIFTS combined with density functional theory calculations reveal that both DCM activation and chlorinated intermediate adsorption preferentially occur on Pt surfaces, which accounts for the rapid inactivation of PCTO under heating conditions. The introduction of light facilitates the generation of reactive oxygen species, which effectively promotes the desorption of chlorine species from the Pt surface via their rapid oxidation to Cl₂, thus alleviating chlorine accumulation on Pt nanoparticles. These findings provide a new perspective for mitigating chlorine poisoning in the catalytic oxidation of CVOCs.