Highly Efficient and Selective Photocatalytic CO2 Reduction by Iron and Cobalt Quaterpyridine Complexes
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Abstract
Summary
A photochemical reduction of CO2 to CO was shown using the cobalt complex [Fe(qpy)(H2O)2][ClO4]2 or the iron complex [Co(qpy)(H2O)2][ClO4]2 as catalysts in combination with the ruthenium-based photosensitizer Ru(bpy)3Cl2. Turnover numbers (TONs) up to 2660 and a selectivity of 98% for CO using the cobalt catalyst and TONs of >3000 and a selectivity of 95% for CO using the iron catalyst were reached in acetonitrile/triethanolamine. When swapping the ruthenium photosensitizer for the organic dye sensitizer purpurin, TONs of 790 and 1365 in DMF were obtained for the cobalt and iron catalysts, respectively. The experiments were conducted under visible-light irradiation (λ = 460 nm) using BIH as sacrificial reductant (see section SEDs below).
Advances and special progress
The photocatalytic reduction of CO2 to CO by cobalt and iron complexes was shown with some of the highest TONs for homogeneous photocatalytic CO2 reduction at that time and the (back then) highest TON for a system of fully earth-abundant materials was achieved.
Additional remarks
Content of the published article in detail
The article contains results for the reduction of CO2 to CO under visible-light catalysis using cobalt and iron quaterpyridine complexes as catalysts. The catalytic system performs best (referring to the TON of CO production) in acetonitrile/triethanolamine using the cobalt complex and the ruthenium photosensitizer.
Catalysts
[Fe(qpy)(H2O)2][ClO4]2
[Co(qpy)(H2O)2][ClO4]2
Co(ClO4)2
Photosensitizers
Investigations
| cat | cat conc [µM] | PS | PS conc [mM] | e-D | e-D conc [M] | . | . | solvent A | additives | λexc [nm] | . | TON CO | TON H2 | TON HCOOH | . | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1. | 0.005 | 0.3 | 0.1 | 460 (LED) | 2660 | 23 | 35 | |||||||||
| 2. | 0 | 0.3 | 0.1 | 460 (LED) | 0 | 2 | 1 | |||||||||
| 3. | 0.005 | 0.3 | 0.1 | Argon atmosphere | 460 (LED) | 0 | 33 | 0 | ||||||||
| 4. | 0.005 | 0.3 | 0.1 | 460 (LED) | 182 | 0 | 11 | |||||||||
| 5. | 0.005 | 0.3 | 460 (LED) | 114 | 25 | 25 | ||||||||||
| 6. | 0.01 | 0.3 | 0.1 | 460 (LED) | 1875 | 11 | 18 | |||||||||
| 7. | 0.2 | 0.3 | 0.1 | 460 (LED) | 1262 | 7 | 23 | |||||||||
| 8. | 0.05 | 0.3 | 0.1 | 460 (LED) | 497 | 5 | 3 | |||||||||
| 9. | 0.05 | 0.3 | 460 (LED) | 0 | 1 | 1 | ||||||||||
| 10. | 0.1 | 0.3 | 0.1 | 460 (LED) | 466 | 2 | 22 | |||||||||
| 11. | 0.05 | 0.5 | 0.1 | 460 (LED) | 521 | 49 | 6 | |||||||||
| 12. | 0 | 0.5 | 0.1 | 460 (LED) | 136 | 43 | 5 | |||||||||
| 13. | 0.05 | 0.2 | 0.1 | 460 (LED) | 366 | 15 | 4 | |||||||||
| 14. | 0.05 | 0.2 | 0.1 | Argon atmosphere | 460 (LED) | 0 | 3 | 1 | ||||||||
| 15. | 0 | 0.2 | 0.1 | 460 (LED) | 0 | 6 | 1 | |||||||||
| 16. | 0.05 | 0.3 | 0.1 | 460 (LED) | 33 | 11 | 1 | |||||||||
| 17. | 0.05 | 0.3 | 460 (LED) | 0 | 1 | 1 |
| cat | cat conc [µM] | PS | PS conc [mM] | e-D | e-D conc [M] | solvent A | . | . | additives | λexc [nm] | . | TON CO | TON H2 | TON HCOOH | . | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1. | 0.05 | 0.2 | 0.1 | 460 (LED) | 1879 | 15 | 48 | |||||||||
| 2. | 0.05 | 0.2 | 0.1 | Argon atmosphere | 460 (LED) | 0 | 1 | 3 | ||||||||
| 3. | 0 | 0.2 | 0.1 | 460 (LED) | 0 | 0 | 0 | |||||||||
| 4. | 0.02 | 0.2 | 0.1 | 460 (LED) | 2660 | 29 | 51 | |||||||||
| 5. | 0.02 | 0.2 | 0.1 | Argon atmosphere | 460 (LED) | 0 | 0 | 0 | ||||||||
| 6. | 0.01 | 0.2 | 0.1 | 460 (LED) | 3087 | 121 | 35 | |||||||||
| 7. | 0.01 | 0.2 | 0.1 | Argon atmosphere | 460 (LED) | 0 | 0 | 0 | ||||||||
| 8. | 0.005 | 0.2 | 0.1 | 460 (LED) | 3844 | 118 | 534 | |||||||||
| 9. | 0.005 | 0.2 | 0.1 | Argon atmosphere | 460 (LED) | 0 | 1 | 0 | ||||||||
| 10. | 0.05 | 0.05 | 0.1 | 460 (LED) | 1336 | 10 | 34 | |||||||||
| 11. | 0.05 | 0.05 | 0.1 | 460 (LED) | 0 | 0 | 0 | |||||||||
| 12. | 0 | 0.05 | 0.1 | 460 (LED) | 0 | 1 | 0 | |||||||||
| 13. | 0.005 | 0.2 | 460 (LED) | 160 | 8 | 22 |
Sacrificial electron donor
In this study, the experiments were done with the sacrificial reductant BIH (100508).
Additives
In this study, control experiments were conducted under an argon atmosphere.
Investigations
- Optimizations of conditions for Co(qpy)(H2O)2(ClO4)2 and Ru(bpy)3Cl2 (Molecular process, Photocatalytic CO2 conversion experiments)
- Optimizations of conditions for Co(qpy)(H2O)2(ClO4)2 and purpurin (Molecular process, Photocatalytic CO2 conversion experiments)
- Optimizations of conditions for Fe(qpy)(H2O)2(ClO4)2 (Molecular process, Photocatalytic CO2 conversion experiments)
- Optimizations of conditions for Fe(qpy)(H2O)2(ClO4)2 and Ru(bpy)3Cl2 (Molecular process, Photocatalytic CO2 conversion experiments)
