Synergy of metal-support interaction and positive Pd species promoting efficient C-Cl bond activation on Pd-based Ce-MOF-derived catalysts

Monochloroacetic acid (MCAA) is identified as a highly carcinogenic disinfection by-product in chlorinated drinking water. In this study, a series of CeO2-supported Pd catalysts (Pd/MCeO2) were synthesized through one-step calcination of Pd-loaded Ce-UiO-66-BDC (Ce-MOF), and the liquid-phase catalytic hydrodechlorination of MCAA was explored using these catalysts. For comparison, Pd/CeO2 catalysts were additionally synthesized using the conventional impregnation method. The characterization results reveal that the catalysts exhibit strong metal-support interaction, leading to high Pd dispersion and Pdn+ content. Additionally, the calcination temperature significantly influences catalytic performance, with the catalyst calcined at 500 degrees C (Pd/MCeO2-500) demonstrating the highest catalytic activity and achieving complete dechlorination of MCAA within 50 min. Furthermore, it is found that the catalytic MCAA hydrodechlorination using the catalysts adheres to the Langmuir-Hinshelwood model. Accordingly, low reaction pH is favorable for the catalytic hydrodechlorination of MCAA, enhancing MCAA adsorption on the catalyst surface due to the electrostatic interaction between MCAA and the catalyst surface. Theoretical results suggest that the presence of Pdn+ efficiently facilitates MCAA adsorption and C-Cl cleavage, thus significantly enhancing the liquid-phase catalytic hydrodechlorination.