Photochemical composition and use thereof for producing CH
The present invention relates to photochemical compositions comprising: a solution comprising an organic solvent, preferably selected from dimethylformamide, acetonitrile, and mixtures thereof with water, a sacrificial electron donor; a proton donor having a pKa in acetonitrile greater than or equal to 28; a photosensitizer whose reduced state has a standard redox potential more negative than −1.45 V vs SCE; and a metal porphyrin complex of formula (I) as defined in claim 1, useful in the production of CH 4 from CO 2 or CO by photochemical catalysis, to a photochemical cell comprising same and to a method for producing CH 4 from CO 2 or CO by photochemical catalysis using same.
1. A photochemical composition for producing methane by reducing at least one of CO 2 and CO at visible light, comprising:
a solution comprising an organic solvent,
a sacrificial electron donor;
a proton donor having a pKa in acetonitrile greater than or equal to 28;
a photosensitizer whose reduced state has a standard redox potential more negative than −1.45 V vs Saturated Calomel Electrode, wherein the photosensitizer is a complex of a transition metal with at least two 2-phenylpyridine (ppy) ligand; and
a metal porphyrin complex of formula (I):
wherein:
M represents a transition metal ion,
R 1 to R 10 and R 1 ′ to R 10 ′ are independently selected from the group consisting of H, OH, F, C 1 -C 6 alcohol, and N + (C 1 -C 4 alkyl) 3 ,
and wherein:
at least one of R 1 to R 5 is OH and at least one of R 1′ to R 5′ is OH, or
at least one of R 1 to R 5 is N + (C 1 -C 4 alkyl) 3 , and at least one of R 1′ to R 5′ is N + (C 1 -C 4 alkyl) 3 ,
and salts thereof.
2. The photochemical composition of claim 1 , wherein the photosensitizer having a standard redox potential more negative than −1.35 V vs Saturated Calomel Electrode in the reduced state is a metal complex of formula (III):
wherein Y 1 , Y 2 and Y 3 are CH 2 , and M′ represents a transition metal.
3. The photochemical composition of claim 1 , wherein the concentration of photosensitizer in the photochemical composition is of between 50 mM and 1 mM.
4. The photochemical composition of claim 1 , wherein the concentration of sacrificial electron donor in the photochemical composition is of between 10 mM and 500 mM.
5. The photochemical composition of claim 1 , wherein the sacrificial electron donor is a tertiary amine.
6. The photochemical composition of claim 5 , wherein the tertiary amine is:
of formula NR 1 R 2 R 3 , in which R 1 , R 2 and R 3 are identical or different and each independently selected from a C 1 -C 6 alkyl group optionally substituted with OH, OC 1 -C 6 alkyl, or COOH; or
of formula (IV):
wherein
X′ is O or NR, with R representing a (C 1 -C 4 )alkyl,
R′ is a (C 1 -C 4 ) alkyl,
R″ is a hydrogen, halogen, CN, or a (C 1 -C 4 ) alkyl, and
Ar 4 is selected from a monocyclic or bicyclic 5- to 10-membered aromatic or heteroaromatic ring, optionally substituted by a halogen, CN, OH, a biaryl group or a monocyclic 5- or 6-membered aromatic or heteroaromatic ring, said monocyclic 5- or 6-membered aromatic or heteroaromatic ring being optionally substituted by a halogen, CN, OH.
7. The photochemical composition of claim 1 , wherein the proton donor is phenol or trifluoroethanol.
8. The photochemical composition of claim 1 , wherein the metal porphyrin complex of formula (I) comprises at least two N + (C 1 -C 4 alkyl) 3 groups.
9. The photochemical composition of claim 1 , wherein, in the metal porphyrin complex of formula (I):
at least one of R 6 to R 10 is OH and at least one of R 6′ to R 10′ is OH, or
at least one of R 6 to R 10 is N + (C 1 -C 4 alkyl) 3 , and at least one of R 6′ to R 10′ is N + (C 1 -C 4 alkyl) 3 .
10. The photochemical composition of claim 1 , wherein in the metal porphyrin complex of formula (I):
R 1 to R 10 and R 1′ to R 10′ are independently H or N + (C 1 -C 4 alkyl) 3 ,
at least one and at most two of R 1 to R 5 represent N + (C 1 -C 4 alkyl) 3 , and
at least one and at most two of R 1′ to R 5′ represent N + (C 1 -C 4 alkyl) 3 .
11. The photochemical composition of claim 1 , wherein the metal porphyrin complex of formula (I) is selected from:
and salts thereof.
12. The photochemical composition of claim 1 , wherein:
the sacrificial electron donor is the tertiary amine of formula NR 1 R 2 R 3 , in which R 1 , R 2 and R 3 are identical or different and each independently selected from a C 1 -C 6 alkyl group optionally substituted with OH, OC 1 -C 6 alkyl, or COOH;
the photosensitizer is the following complex:
the metal porphyrin complex is
the solvent is acetonitrile;
phenol or trifluoroethanol as a proton donor.
13. The photochemical composition of claim 1 , wherein the concentration of the metal porphyrin complex of formula (I) as defined in claim 1 is between 1 mM and 50 mM.
14. A method for producing methane from CO 2 or CO, said method comprising:
a) contacting gaseous CO 2 or CO, with a photochemical composition as claimed in claim 1 to obtain a solution comprising dissolved at least one of CO 2 and CO;
b) irradiation of said solution with visible light; and
c) collecting methane.
15. The method of claim 14 , wherein the pressure of CO 2 or CO of less than 1 bar.
16. The method of claim 14 , wherein the pressure of CO 2 or CO is of 1 bar or more.
17. The method of claim 14 , wherein:
the concentration of a sacrificial electron donor is between 10 mM and 500 mM,
the concentration of the photosensitizer is between 50 mM and 1 mM,
the concentration of the metal porphyrin complex of formula (I) is between 1 mM and 50 mM, the concentration of a proton donor is between 1 mM and 1 M.
18. The method of claim 14 , wherein the irradiation lasts several days with wavelength λ of 400 nm or more, the reaction being stable.