Defect-derived catalytic sites in Ce/Zr-UiO-66 for degradation of hexachlorobenzene

Abstract

It is of great significance to develop catalysts for the degradation of hexachlorobenzene from the industrial thermal process. In this paper, formic acid was used as a modulator to generate defect sites in Ce/Zr-UiO-66 with intrinsic Brønsted acidity. The defective formate ligands were removed through methanol–water vapor treatment to expose additional open metal sites with Lewis acidity. The intrinsic Brønsted acid sites of the resulting Ce/Zr-UiO-66-FA-P achieved a hexachlorobenzene degradation efficiency of 99.5% at 250 °C. The generated Lewis acid sites facilitated the C–C cleavage of degradation intermediates. More than 95.0% of the final products were CO₂/CO, coupled with chlorinated alkanes/alkenes, which outperformed other benchmark metal oxide catalysts. The Ce/Zr-UiO-66-FA-P catalyst maintained its catalytic activity in the model industrial flue gas and humid environment. The degradation pathway of hexachlorobenzene was tracked using in situ FT-IR spectra.