Photoreductive Dehalogenation of Bromoform with Titanium Dioxide-Cobalt Macrocycle Hybrid Catalysts

Ronald J. Kuhler, Gregory A. Santo, Thomas R. Caudill, Eric A. Betterton, Robert G. Arnold

Research output: Contribution to journalArticlepeer-review

24 Scopus citations

Abstract

The hybrid semiconductor-macrocycle catalyst, TiO2-Cotetrasulfophthalocyanine, (TiO2—CoTSP) effectively enhances the solar-promoted reductive dehalogenation of bromoform (CHBr3) under anaerobic conditions. Reaction rates are 4–10 times faster than those obtained using silanized TiO2, unmodified TiO2, or direct (uncatalyzed) solar photolysis under the same conditions. CHBr3 is reduced to its lower homologues, dibromomethane (CH2—Br2), and bromomethane (CH3Br). HBr is also produced. No other major dehalogenation products are observed, although methane is found in trace amounts after prolonged photolysis. 2-Propanol, the sacrificial electron donor, is oxidized stoichiometrically to acetone. The catalyst is stable in sunlight for at least 30 h without loss of activity. The reaction mechanism is postulated to involve nucleophilic attack of Co(I)TSP, generated by the semiconductor, on CHBr3. The organometallic complex that is formed, TiO2—CoTSP—CHBr2, is postulated to subsequently undergo photolysis via homolytic Co—C bond cleavage to regenerate the catalyst. 2-Propanol is oxidized by valence band holes.

Original languageEnglish (US)
Pages (from-to)2104-2111
Number of pages8
JournalEnvironmental Science and Technology
Volume27
Issue number10
DOIs
StatePublished - 1993

ASJC Scopus subject areas

  • Chemistry(all)
  • Environmental Chemistry

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