Cyclodextrin-Assisted Synthesis of Pd/Co/C Nanopolyhedra by ZIF-67 as a Highly Acid Tolerant Catalyst for Hexavalent Chromium Reduction

The palladium/cobalt/carbon (Pd/Co/C) nanopolyhedra were synthesized by calcinating the precursor prepared by a cyclodextrin (CD) modified palladium acetylacetonate loaded on ZIF-67, hydroxypropyl-β-cyclodextrin (HP-β-CD)–[Pd­(acac)₂]/ZIF-67. On one hand, the HP-β-CD was used to increase the solubility of Pd­(acac)₂ by supramolecular interactions, and on the other hand, ZIF-67 was employed to provide the Co/C as the magnetic support. The Pd/Co/C nanopolyhedra obtained with the assistance of HP-β-CD have high activity and reusability for the reduction of the dichromate ion in the presence of formic acid without using any buffer solution, and no significant leaching of metallic Co of the catalyst was observed. This could be ascribed to the fact that the presence of HP-β-CD could lead to a more homogeneous distribution of metallic Pd in the Pd/Co/C nanopolyhedra, which could prevent the dissolution of metallic Co by formic acid.