Porphyrin molecular catalysts for selective electrochemical reduction of CO

1. A porphyrin of formula (I):

wherein

R 1 , R 1′ , R 2 and R 2′ independently represent H, OH, F, N + R 7 R 8 R 9 , C 1 -C 4 alkyl or C 1 -C 4 -alcohol,

R 3 , R 3′ , R 6 and R 6′ are independently selected from the group consisting of H, OH, F and C 1 -C 4 -alcohol,

R 4 , R 4′ , R 5 , R 5′ are independently selected from the group consisting of H, OH, F, C 1 -C 4 alkyl, C 1 -C 4 -alcohol, or N + R 7 R 8 R 9 ,

X and X′ independently represent CH, CF, CN + R 7 R 8 R 9 , or N + R 7 ,

Y and Y′ independently represent CH, CF, CN + R 7 R 8 R 9 , or N + R 7 ,

R 7 , R 8 and R 9 independently of each other represent H or a C 1 -C 4 alkyl group,

provided that at least one of X, X′, Y and Y′ represents CF, CN + R 7 R 8 R 9 , or N + R 7 , or at least one of R 3 , R 3′ , R 6 and R 6′ represents F or at least one of R 1 , R 1′ , R 2 , R 2′ , R 4 , R 4′ , R 5 , and R 5′ represents F or N + R 7 R 8 R 9 ,

and salts thereof.

2. The porphyrin of claim 1 , wherein at least one of X, X′, Y or Y′ represents CF, CN+R 7 R 8 R 9 , or N + R 7 or at least one of R 1 , R 1′ , R 2 , R 2′ , R 4 , R 4′ , R 5 , R 5′ represents F or N + R 7 R 8 R 9 , with R 7 , R 8 and R 9 are as described in claim 1 .

3. The porphyrin of claim 1 , wherein it is of formula (III):

with R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , X and Y are as defined in claim 1 .

4. The porphyrin of claim 1 , wherein X and X′ independently represent CH or CF.

5. The porphyrin of claim 1 , wherein R 3 , R 3′ , R 4 , R 4′ , R 5 , R 5′ , R 6 , and R 6′ are independently selected from the group consisting of H and F.

6. The porphyrin of claim 1 , wherein at least one of Y, Y′, X and X′ is CN + R 7 R 8 R 9 or at least one of R 1 , R 1′ , R 2 , R 2′ , R 4 , R 4′ , R 5 , and R 5′ is N + R 7 R 8 R 9 , with R 7 , R 8 and R 9 defined in claim 1 .

7. The porphyrin of claim 6 , wherein it is of the following formula:

wherein R 7 , R 8 and R 9 as independently of each other represent H or a C 1 -C 4 alkyl group.

8. The porphyrin of claim 1 , wherein it is:

9. A complex of a porphyrin according to claim 1 with a transition metal and salts thereof.

10. The complex of claim 9 , wherein the transition metal is iron.

11. An electrochemical cell comprising at least:

an electrolyte solution comprising the solvent, a supporting electrolyte, and the substrate CO 2 ,

a power supply providing the energy necessary to trigger the electrochemical reactions involving the substrate, and

two electrodes, an anode and a cathode,

wherein the electrochemical cell further comprises the complex of claim 8 .

12. The electrochemical cell of claim 11 , wherein the complex is in a concentration, in the electrolyte solution, of between 0.0005 and 0.01 M.

13. The electrochemical cell of claim 11 , wherein the electrolyte further comprises a proton donor selected from the group consisting of water (H 2 O), trifluoroethanol, phenol and acetic acid.

14. The electrochemical cell of claim 11 , wherein the complex is in the electrolyte solution.

15. A method of reducing electrochemically CO 2 into CO using the complex of claim 9 as catalyst or an electrochemical cell comprising at least:

an electrolyte solution comprising the solvent, a supporting electrolyte, and the substrate CO 2 ,

a power supply providing the energy necessary to trigger the electrochemical reactions involving the substrate,

two electrodes, an anode and a cathode, and

the complex of claim 9 .

16. The method of claim 15 , wherein the method is carried out in the presence of a proton donor.

17. The method of claim 15 , wherein the potential applied to the cathode is between −2.5 V and −0.5 V versus NHE.

18. The method of claim 15 , wherein the proton donor is selected from the group consisting of water, trifluoroethanol, phenol and acetic acid.

19. The method of claim 15 , wherein the intensity applied to the cathode is between 2 and 5 A/m 2 .