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

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.