Letter | Published:

Visible-light-driven methane formation from CO2 with a molecular iron catalyst

Nature volume 548, pages 7477 (03 August 2017) | Download Citation


Converting CO2 into fuel or chemical feedstock compounds could in principle reduce fossil fuel consumption and climate-changing CO2 emissions1,2. One strategy aims for electrochemical conversions powered by electricity from renewable sources3,4,5, but photochemical approaches driven by sunlight are also conceivable6. A considerable challenge in both approaches is the development of efficient and selective catalysts, ideally based on cheap and Earth-abundant elements rather than expensive precious metals7. Of the molecular photo- and electrocatalysts reported, only a few catalysts are stable and selective for CO2 reduction; moreover, these catalysts produce primarily CO or HCOOH, and catalysts capable of generating even low to moderate yields of highly reduced hydrocarbons remain rare8,9,10,11,12,13,14,15,16,17. Here we show that an iron tetraphenylporphyrin complex functionalized with trimethylammonio groups, which is the most efficient and selective molecular electro- catalyst for converting CO2 to CO known18,19,20, can also catalyse the eight-electron reduction of CO2 to methane upon visible light irradiation at ambient temperature and pressure. We find that the catalytic system, operated in an acetonitrile solution containing a photosensitizer and sacrificial electron donor, operates stably over several days. CO is the main product of the direct CO2 photoreduction reaction, but a two-pot procedure that first reduces CO2 and then reduces CO generates methane with a selectivity of up to 82 per cent and a quantum yield (light-to-product efficiency) of 0.18 per cent. However, we anticipate that the operating principles of our system may aid the development of other molecular catalysts for the production of solar fuels from CO2 under mild conditions.

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This work was partially supported by the CNRS, Défi Transition énergétique “Emergence CO2” (the PERIODIC project). H.R. thanks the China Scholarship Council for a PhD fellowship (CSC student number 201507040033). We thank D. Clainquart (Université Paris Diderot) for assistance in gas chromatography/mass spectrometry analysis and I. Azcarate for porphyrin synthesis.

Author information


  1. Université Paris Diderot, Sorbonne Paris Cité, Laboratoire d’Electrochimie Moléculaire, UMR 7591 CNRS, 15 rue Jean-Antoine de Baïf, F-75205 Paris Cedex 13, France

    • Heng Rao
    • , Luciana C. Schmidt
    • , Julien Bonin
    •  & Marc Robert
  2. INFIQC-CONICET, Departamento de Química Orgánica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, 5000 Córdoba, Argentina

    • Luciana C. Schmidt


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M.R. conceived the research, J.B. and M.R. directed the project and co-wrote the paper. J.B. conceived the experimental setup. J.B., L.C.S. and H.R. conducted experiments. H.R., J.B. and M.R. analysed results. All the authors contributed to the scientific interpretation and reviewed the manuscript.

Competing interests

The authors declare no competing financial interests.

Corresponding authors

Correspondence to Julien Bonin or Marc Robert.

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