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Iron-based catalyst reduces CO2 to CH4 photochemically

Inexpensive complex turns the greenhouse gas into fuel at ambient temperature and pressure

by Stu Borman
July 24, 2017 | A version of this story appeared in Volume 95, Issue 30

Researchers have been trying to develop efficient techniques that use electrical or sun energy to convert carbon dioxide to methane to supplement fossil-fuel sources and reduce climate-changing CO2 in the atmosphere. But few CO2-reduction catalysts have long-lasting stability and high selectivity for specific products, instead of product mixtures. And the reductions generally produce carbon monoxide, formic acid, or hydrocarbon-oxygenate mixtures. Marc Robert, Julien Bonin, and coworkers at Paris Diderot University now report that an inexpensive iron-based tetraphenylporphyrin catalyst (shown), in the presence of an iridium-phenylpyridine photosensitizer, photochemically reduces CO2 to CO and then to CH4 at ambient temperature and pressure (Nature 2017, DOI: 10.1038/nature23016). The catalyst is stable when used over several days, and its selectivity for CH4 is up to 82%, compared with 35% or less for previous catalysts. CO2 reduction expert Paul J. A. Kenis of the University of Illinois, Urbana-Champaign, comments that CH4 derived from natural gas is currently cheap, making it hard for chemical synthesis to compete, but achieving high selectivity for CH4 with an Earth-abundant catalyst is “a significant achievement.”


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