Light-Driven CH Oxygenation of Methane into Methanol and Formic Acid by Molecular Oxygen Using a Perfluorinated Solvent

Light-Driven CH Oxygenation of Methane into Methanol and Formic

Acid by Molecular Oxygen Using a Perfluorinated Solvent

Angew. Chem. Int. Ed. 2017, 56, 1-5 

http://onlinelibrary.wiley.com/doi/10.1002/anie.201710945/epdf

Abstract:

The chlorine dioxide radical (ClO2·) was found to act as an efficient oxidizing agent in the aerobic oxygenation of methane to methanol and formic acid under photoirradiation. Photochemical oxygenation of methane occurred in a two-phase system comprising perfluorohexane and water under

ambient conditions (298 K, 1 atm). The yields of methanol and formic acid were 14 and 85 %, respectively, with a methane conversion of 99% without formation of the further oxygenated products such as CO2and CO. Ethane was also photochemically converted into ethanol (19%) and acetic acid (80%). The methane oxygenation is initiated by the photochemical Cl-O bond cleavage of ClO2· to generate Cl· and O2. The produced Cl· reacts with CH4 to form a methyl radical (CH3·). Finally, the oxygenated products such as methanol and formic acid were given by the radical chain reaction. A fluorous solvent plays an important role of inhibiting the deactivation of reactive radical species such as Cl· and CH3·.

Efficient Light-Driven Water Oxidation Catalysis by Dinuclear Ruthenium Complexes

Dr. Serena Berardi, Dr. Laia Francas, Sven Neudeck, Dr. Somnath Maji, Dr. Jordi Benet-Buchholz, Prof. Dr. Franc Meyer, Prof. Dr. Antoni Llobet

Abstract

Mastering the light-induced four-electron oxidation of water to molecular oxygen is a key step towards the achievement of overall water splitting to produce alternative solar fuels. In this work, we report two rugged molecular pyrazolate-based diruthenium complexes that efficiently catalyze visible-light-driven water oxidation. These complexes were fully characterized both in the solid state (by X-ray diffraction analysis) and in solution (spectroscopically and electrochemically). Benchmark performances for homogeneous oxygen production have been obtained for both catalysts in the presence of a photosensitizer and a sacrificial electron acceptor at pH 7, and a turnover frequency of up to 11.1 s⁻¹ and a turnover number of 5300 were obtained after three successive catalytic runs. Under the same experimental conditions with the same setup, the pyrazolate-based diruthenium complexes outperform other well-known water oxidation catalysts owing to both electrochemical and mechanistic aspects.

http://onlinelibrary.wiley.com/doi/10.1002/cssc.201500798/full