Editing Visible-Light-Driven Conversion of CO2 to CH4 with an Organic Sensitizer and an Iron Porphyrin Catalyst

{{BaseTemplate}}
{{DOI|doi=10.1021/jacs.8b09740}}

=== Abstract ===

==== Summary ====
A photochemical reduction of CO<sub>2</sub> to CO and CH<sub>4</sub> was shown using the iron porphyrin catalyst {{#moleculelink:|link=LKNRTBVZMCBYCY-NGWNFTKISA-I|image=false|width=300|height=200}} in combination with the phenoxazine photosensitizers {{#moleculelink:|link=HPIOBCHPZVAATK-UHFFFAOYSA-N|image=false|width=300|height=200}} and {{#moleculelink:|link=IGGSSEOAGCUGDJ-UHFFFAOYSA-N|image=false|width=300|height=200}}. Turnover numbers (TONs) up to 149 for CO and 29 for CH<sub>4</sub> were reached. The experiments were conducted under visible-light irradiation (λ > 435 nm) with a tertiary amine (see section SEDs below) as sacrificial electron donor. 

==== Advances and special progress ====
The first demonstration for the reduction of CO<sub>2</sub> to CH<sub>4</sub> (complete 8e''<sup>–</sup>''/8H<sup>+</sup> reduction) by a combination of an earth-abundant metal catalyst and an organic dye. So far, similar systems were shown to induce 2e<sup>–</sup>/2H<sup>+</sup> reduction of CO<sub>2</sub> to CO or formic acid. 

==== Additional remarks ====
Methane was produced continuously (even after irradiation up to 4 days). The 8e''<sup>–</sup>''/8H<sup>+</sup> reduction efficiency strongly depends on the redox properties of the organic photosensitizer and acidity of the proton source. In additional experiments, CO was used as the gas resource. The system consisting of  iron porphyrin catalyst {{#moleculelink:|link=LKNRTBVZMCBYCY-NGWNFTKISA-I|image=false|width=300|height=200}} in combination with the phenoxazine photosensitizer {{#moleculelink:|link=IGGSSEOAGCUGDJ-UHFFFAOYSA-N|image=false|width=300|height=200}} was able to produce CH<sub>4</sub> with a TON of 80 (85% selectivity, quantum yield: 0.47%). 

=== Content of the published article in detail ===
The article contains results for the reduction of CO2 and CO as feedstock gases. The catalytic system performs best (referring to the TON of CH<sub>4</sub> production) for CO as a feedstock.   

==== Catalysts ====
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  -INDIGO-11282314292D

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M  V30 46 C 12.6043 -7.94076 0.0 0
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M  V30 49 C 10.673 -8.46539 0.0 0
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M  V30 54 C 2.90363 -1.03828 0.0 0
M  V30 55 C 3.06254 0.168823 0.0 0
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M  V30 60 C 13.9201 -9.11372 0.0 0
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M  V30 9 1 9 10
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M  V30 75 8 3 65
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M  V30 END BOND
M  V30 END CTAB
M  END
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==== Photosensitizers ====
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  -INDIGO-11092309282D

  0  0  0  0  0  0  0  0  0  0  0 V3000
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M  V30 BEGIN BOND
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M  V30 4 1 2 3
M  V30 5 2 5 6
M  V30 6 1 6 4
M  V30 7 1 8 7
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M  V30 9 1 7 2
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M  V30 36 1 31 28
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M  V30 END BOND
M  V30 END CTAB
M  END
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  -INDIGO-12132211312D

  0  0  0  0  0  0  0  0  0  0  0 V3000
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M  V30 4 1 2 3
M  V30 5 2 5 6
M  V30 6 1 6 4
M  V30 7 1 8 7
M  V30 8 1 4 9
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M  V30 16 1 14 12
M  V30 17 2 17 15
M  V30 18 2 18 16
M  V30 19 1 15 19
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M  V30 21 2 19 20
M  V30 22 1 20 18
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M  V30 24 2 24 22
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M  V30 27 2 25 26
M  V30 28 1 26 24
M  V30 29 2 29 27
M  V30 30 2 30 28
M  V30 31 1 27 31
M  V30 32 1 28 29
M  V30 33 2 31 32
M  V30 34 1 32 30
M  V30 35 2 35 33
M  V30 36 2 36 34
M  V30 37 1 33 37
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M  V30 39 2 37 38
M  V30 40 1 38 36
M  V30 41 2 41 39
M  V30 42 2 42 40
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M  V30 45 2 43 44
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M  V30 51 1 48 46
M  V30 52 1 5 28
M  V30 53 1 31 34
M  V30 54 1 14 15
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M  V30 56 1 7 44
M  V30 END BOND
M  V30 END CTAB
M  END
</chemform>

==== Investigations ====
{{#experimentlist:|form=Photocatalytic_CO2_conversion_experiments|name=Table 1}}

==== Sacrificial Electron Donor ====
In this study, the experiments were done with the sacrificial electron donors DIPEA ({{#moleculelink:|link=JGFZNNIVVJXRND-UHFFFAOYSA-N|image=false|width=300|height=200}}), TEOA ({{#moleculelink:|link=GSEJCLTVZPLZKY-UHFFFAOYSA-N|image=false|width=300|height=200}}), BIH ({{#moleculelink:|link=VDFIVJSRRJXMAU-UHFFFAOYSA-N|image=false|width=300|height=200}}), and TEA ({{#moleculelink: |link=ZMANZCXQSJIPKH-UHFFFAOYSA-N|image=false|width=300|height=200}}).

==== Additives ====
In this study, different additives were used. As depicted in the investigation table, water ({{#moleculelink:|link=XLYOFNOQVPJJNP-UHFFFAOYSA-N|image=false|width=300|height=200}},) phenol ({{#moleculelink:|link=ISWSIDIOOBJBQZ-UHFFFAOYSA-N|image=false|width=300|height=200}}), and trifluoroethanol ({{#moleculelink:|link=RHQDFWAXVIIEBN-UHFFFAOYSA-N|image=false|width=300|height=200}}) were used. 
[[Category:Photocatalytic CO2 conversion to CH4]]