Sol-gel entrapped Au0- and Ag0-nanoparticles catalyze reductive de-halogenation of halo-organic compounds by BH4

Jaydeep Adhikary, Dan Meyerstein, Vered Marks, Michael Meistelman, Gregory Gershinsky, Ariela Burg, Dror Shamir, Haya Kornweitz, Yael Albo

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16 Scopus citations

Abstract

This study investigated the reductive de-halogenations of toxic Br3CCO2, Br2CHCO2, BrCH2CO2, CH3CHBrCO2, CH2BrCH2CO2, CH2BrCHBrCO2, Cl3CCO2, Cl2CHCO2- and ClCH2CO2 by sodium borohydride catalyzed by sol-gel silica entrapped Au0 and Ag0 nanoparticles. The results indicate that the mechanism of reduction of Br3CCO2 differs from that of Cl3CCO2. Calculated by DFT, the source of this difference lies in the larger bond strength of C–Cl compared to that of C–Br and the weaker M0–C bond strength in Au0-CBr2CO2 compared to those of Au0-CCl2CO2 and Au0-CH2CO2. Furthermore, the de-halogenation mechanisms catalyzed by Ag0-NPs differ from those catalyzed by Au0-NPs. The latter observation is attributed to the different Ag–C and Au–C bond strengths and to the different over-potentials for H2 release of these M0-NPs. In addition, product composition depends on the rate of BH4 addition. Proton labeling experiments prove that nearly all the hydrogen atoms in the products originated from the water solvent and not from the BH4. The detailed mechanistic conclusions that can be drawn from these results differ considerably from those commonly accepted for de-halogenation processes.

Original languageEnglish
Pages (from-to)450-462
Number of pages13
JournalApplied Catalysis B: Environmental
Volume239
DOIs
StatePublished - 30 Dec 2018

Keywords

  • Dehalogenation
  • Gold and silver nanoparticles
  • Mechanistic study
  • Silica matrix
  • Sol-gel

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