Mn-carbonyl molecular catalysts containing a redox-active phenanthroline-5,6-dione for selective electro- and photoreduction of CO2 to CO or HCOOH
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Abstract
Summary
A photochemical reduction of CO2 to CO or formic acid was shown using the manganese complexes Mn(phdk)(CO)3Br or Mn(phdk)(CO)3(MeCN) as catalyst in combination with the ruthenium-based photosensitizer Ru(bpy)3Cl2, comparing the results to the previously reported catalysts Mn(phen)(CO)3Br and Mn(bpy)(CO)3Br. Turnover numbers (TONs) of 58 for formic acid were reached in acetonitrile with complex Mn(phdk)(CO)3(MeCN). The experiments were conducted under visible-light irradiation (λ = 480 or 500 nm) using TEOA and BNAH as sacrificial electron donors (see section SEDs below).
Advances and special progress
The efficiency of formic acid generation from CO2 was improved compared to a previously reported manganese complex. The increased water solubility of one of the novel complexes may enable photo- or electrocatalytic CO2 reduction in aqueous media.
Additional remarks
In electrochemical CO2 reduction experiments, a high selectivity for CO formation was observed, contrary to the preferential formation of formic acid in the photocatalytic CO2 reduction.
Content of the published article in detail
The article contains results for the reduction of CO2 to formic acid under visible-light catalysis using manganese complexes as catalysts. The catalytic system performs best (referring to the TON of formic acid production) in acetonitrile using catalyst Mn(phdk)(CO)3(MeCN).
Catalyst
Mn(phdk)(CO)3Br
Mn(phdk)(CO)3(MeCN)
Mn(phen)(CO)3Br
Mn(bpy)(CO)3Br
Photosensitizer
Investigation
| cat | cat conc [µM] | PS | PS conc [mM] | e-D | e-D conc [M] | solvent A | . | . | . | additives | λexc [nm] | . | TON CO | TON HCOOH | . | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1. | 100 | 0.1 | 480 | 8 | 52 | |||||||||||
| 2. | 100 | 0.1 | 480 | 15 | 58 | |||||||||||
| 3. | 100 | 0.1 | 480 | 9 | 48 | |||||||||||
| 4. | 100 | 0.1 | 480 | 47 | 15 | |||||||||||
| 5. | 100 | 0.1 | 500 | 7 | 40 | |||||||||||
| 6. | 100 | 0.1 | 457 | 7 | 34 | |||||||||||
| 7. | 2 | 100 | 0.1 | 480 | 5 | 18 | ||||||||||
| 8. | 200 | 0.1 | 480 | 8 | 52 | |||||||||||
| 9. | 100 | 0.1 | 480 | |||||||||||||
| 10. | 100 | 0.1 | 500 | |||||||||||||
| 11. | 100 | 480 | 3 | |||||||||||||
| 12. | 0.1 | 500 | ||||||||||||||
| 13. | 100 | 0.1 | Argon gas | 480 | ||||||||||||
| 14. | 100 | 0.1 | 480 | |||||||||||||
| 15. | 100 | 0.1 | 480 | |||||||||||||
| 16. | 100 | 0.1 | 480 | 21 | 22 | |||||||||||
| 17. | 100 | 0.1 | 480 | 2 | ||||||||||||
| 18. | 100 | 480 | 9 | 13 | ||||||||||||
| 19. | 100 | 0.1 | 480 | 17 | 4 | |||||||||||
| 20. | 100 | 0.1 | 480 | 6 | 39 | |||||||||||
| 21. | 100 | ascorbic acid/NaA | 480 | |||||||||||||
| 22. | 100 | ascorbic acid/NaA | 500 |
Sacrificial electron donor
In this study, the experiments were done with the sacrificial electron donors TEOA (100507) and BNAH (BNAH).
Additives
In this study, ascorbic acid was tested as an additive and control experiments under argon atmosphere were performed.
Investigations
- Table 1 (Molecular process, Photocatalytic CO2 conversion experiments)
