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Bio-inspired cofacial Fe porphyrin dimers for efficient electrocatalytic CO2 to CO conversion: Overpotential tuning by substituents at the porphyrin rings.

Zahran ZN, Mohamed EA, Naruta Y - Sci Rep (2016)

Bottom Line: Efficient reduction of CO2 into useful carbon resources particularly CO is an essential reaction for developing alternate sources of fuels and for reducing the greenhouse effect of CO2.The binuclear Ni, Fe-containing carbon monoxide dehydrogenase (CODHs) efficiently catalyzes the reduction of CO2 to CO.By introducing electron-withdrawing/-donating groups, e.g. electron-withdrawing perfluorophenyl, at all meso positions of the porphyrin rings, the catalysis overpotential, η was minimized by ≈0.3 V compared to that obtained by introducing electron-donating mesityl groups.

View Article: PubMed Central - PubMed

Affiliation: Institute for Science and Technology Research, Centre for Chemical Energy Conversion, Chubu University, Kasugai 487-8501, Japan.

ABSTRACT
Efficient reduction of CO2 into useful carbon resources particularly CO is an essential reaction for developing alternate sources of fuels and for reducing the greenhouse effect of CO2. The binuclear Ni, Fe-containing carbon monoxide dehydrogenase (CODHs) efficiently catalyzes the reduction of CO2 to CO. The location of Ni and Fe at proper positions allows their cooperation for CO2 to CO conversion through a push-pull mechanism. Bio-inspired from CODHs, we used several cofacial porphyrin dimers with different substituents as suitable ligands for holding two Fe ions with suitable Fe-Fe separation distance to efficiently and selectively promote CO2 to CO conversion with high turnover frequencies, TOFs. The substituents on the porphyrin rings greatly affect the catalysis process. By introducing electron-withdrawing/-donating groups, e.g. electron-withdrawing perfluorophenyl, at all meso positions of the porphyrin rings, the catalysis overpotential, η was minimized by ≈0.3 V compared to that obtained by introducing electron-donating mesityl groups. The Fe porphyrin dimers among reported catalysts are the most efficient ones for CO2 to CO conversion. Control experiments indicate that the high performance of the current CO2 to CO conversion catalysts is due to the presence of binuclear Fe centers at suitable Fe-Fe separation distance.

No MeSH data available.


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Chemical structures of the six Fe porphyrin dimers and their corresponding monomers.
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f1: Chemical structures of the six Fe porphyrin dimers and their corresponding monomers.

Mentions: Inspired from the Ni, Fe−containing CODHs, we recently reported a cofacial Fe tetraphenylporphyrin dimer, o-Fe2DTPP having binuclear Fe centers at a suitable Fe−Fe separation distance that efficiently and selectively catalyzes the electrochemical CO2 to CO conversion in a DMF/10% H2O solution with high Faradic efficiency (95%) and TOF (4,300 s−1) without use of any acids. However, its reaction showed a relatively high overpotential, η = 0.66 V. Control experiments with the mononuclear Fe porphyrin monomer, FeTPP and the 1,3-phenylene bridged binuclear Fe porphyrin dimer, m-Fe2DTPP indicate the importance of the binuclear Fe centers and the Fe−Fe separation distance for the CO2 to CO conversion49. Here we introduced electron-donating and electron-withdrawing substituents to the peripheral porphyrin rings (Fig. 1) that tuned η and the activity of the catalytic process. We also performed control experiments with Fe porphyrin monomers (Fig. 1) that show low activity for CO2 reduction compared to that obtained with the binuclear Fe porphyrin dimers that clearly demonstrate the importance of the binuclear metal centers for the high activity and stability in designing CO2 to CO conversion molecular catalysts. Benchmarking with other catalysts, the binuclear Fe porphyrin dimers are, to the best of our knowledge, the most efficient and stable homogeneous molecular catalysts for CO2 to CO conversion at present.


Bio-inspired cofacial Fe porphyrin dimers for efficient electrocatalytic CO2 to CO conversion: Overpotential tuning by substituents at the porphyrin rings.

Zahran ZN, Mohamed EA, Naruta Y - Sci Rep (2016)

Chemical structures of the six Fe porphyrin dimers and their corresponding monomers.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4834491&req=5

f1: Chemical structures of the six Fe porphyrin dimers and their corresponding monomers.
Mentions: Inspired from the Ni, Fe−containing CODHs, we recently reported a cofacial Fe tetraphenylporphyrin dimer, o-Fe2DTPP having binuclear Fe centers at a suitable Fe−Fe separation distance that efficiently and selectively catalyzes the electrochemical CO2 to CO conversion in a DMF/10% H2O solution with high Faradic efficiency (95%) and TOF (4,300 s−1) without use of any acids. However, its reaction showed a relatively high overpotential, η = 0.66 V. Control experiments with the mononuclear Fe porphyrin monomer, FeTPP and the 1,3-phenylene bridged binuclear Fe porphyrin dimer, m-Fe2DTPP indicate the importance of the binuclear Fe centers and the Fe−Fe separation distance for the CO2 to CO conversion49. Here we introduced electron-donating and electron-withdrawing substituents to the peripheral porphyrin rings (Fig. 1) that tuned η and the activity of the catalytic process. We also performed control experiments with Fe porphyrin monomers (Fig. 1) that show low activity for CO2 reduction compared to that obtained with the binuclear Fe porphyrin dimers that clearly demonstrate the importance of the binuclear metal centers for the high activity and stability in designing CO2 to CO conversion molecular catalysts. Benchmarking with other catalysts, the binuclear Fe porphyrin dimers are, to the best of our knowledge, the most efficient and stable homogeneous molecular catalysts for CO2 to CO conversion at present.

Bottom Line: Efficient reduction of CO2 into useful carbon resources particularly CO is an essential reaction for developing alternate sources of fuels and for reducing the greenhouse effect of CO2.The binuclear Ni, Fe-containing carbon monoxide dehydrogenase (CODHs) efficiently catalyzes the reduction of CO2 to CO.By introducing electron-withdrawing/-donating groups, e.g. electron-withdrawing perfluorophenyl, at all meso positions of the porphyrin rings, the catalysis overpotential, η was minimized by ≈0.3 V compared to that obtained by introducing electron-donating mesityl groups.

View Article: PubMed Central - PubMed

Affiliation: Institute for Science and Technology Research, Centre for Chemical Energy Conversion, Chubu University, Kasugai 487-8501, Japan.

ABSTRACT
Efficient reduction of CO2 into useful carbon resources particularly CO is an essential reaction for developing alternate sources of fuels and for reducing the greenhouse effect of CO2. The binuclear Ni, Fe-containing carbon monoxide dehydrogenase (CODHs) efficiently catalyzes the reduction of CO2 to CO. The location of Ni and Fe at proper positions allows their cooperation for CO2 to CO conversion through a push-pull mechanism. Bio-inspired from CODHs, we used several cofacial porphyrin dimers with different substituents as suitable ligands for holding two Fe ions with suitable Fe-Fe separation distance to efficiently and selectively promote CO2 to CO conversion with high turnover frequencies, TOFs. The substituents on the porphyrin rings greatly affect the catalysis process. By introducing electron-withdrawing/-donating groups, e.g. electron-withdrawing perfluorophenyl, at all meso positions of the porphyrin rings, the catalysis overpotential, η was minimized by ≈0.3 V compared to that obtained by introducing electron-donating mesityl groups. The Fe porphyrin dimers among reported catalysts are the most efficient ones for CO2 to CO conversion. Control experiments indicate that the high performance of the current CO2 to CO conversion catalysts is due to the presence of binuclear Fe centers at suitable Fe-Fe separation distance.

No MeSH data available.


Related in: MedlinePlus