Function-Integrated Ru Catalyst for Photochemical CO2 Reduction

Abstract

Summary

A photochemical reduction of CO₂ to CO was shown using the ruthenium catalyst and sensitizer Ru(dppq)(tpy)(MeCN). Turnover numbers (TONs) up to 353 and a selectivity of 97% for CO were reached in dimethylacetamide/water. The experiments were conducted under visible-light irradiation (λ = 420-750 nm) with BIH or TEOA (see section SEDs below) as sacrificial electron donors.

Advances and special progress

The authors describe the at that time first example of a nonsensitized Ru(II) photocatalyst for CO₂ reduction. The reported catalyst showed a higher TON and selectivity than previously reported nonsensitized photocatalysts.

Additional remarks

The product selectivity can be tuned by modification of the basicity of the reaction media. Formic acid can be produced with a selectivity of >99% and a TON of 14 when switching to a dimethylacetamide/TEOA mixture.

Content of the published article in detail

The article contains results for the reduction of CO₂ to CO under visible-light catalysis using a ruthenium as a catalyst without the need for an additional sensitizer. The catalytic system performs best (referring to the TON of CO production) in dimethylacetamide/water and can be modified to produce formic acid in dimethylacetamide/TEOA.

Catalyst/Photosensitizer

Ru(dppq)(tpy)(MeCN)

Investigation

	cat	cat conc [µM]	e-D	e-D conc [M]	solvent A	.	.	additives	λexc [nm]	.	TON CO	.	.	TON H2	TON HCOOH	.	.
1.	Ru(dppq)(tpy)(MeCN)	0.04	BIH	0.1	DMA				420-750		58			1	3
2.	Ru(dppq)(tpy)(MeCN)	0.04	BIH	0.1	DMA			Argon atmosphere	420-750
3.			BIH	0.1	DMA				420-750
4.	Ru(dppq)(tpy)(MeCN)	0.04			DMA				420-750
5.	Ru(dppq)(tpy)(MeCN)	0.04	BIH	0.1	DMA				dark
6.	Ru(dppq)(tpy)(MeCN)	0.04	TEOA		DMA				420-750						14

Experiment-Name: Control experimentsExport

The catalyst acts also as photosensitizer

	cat	cat conc [µM]	e-D	e-D conc [M]	solvent A	.	.	.	λexc [nm]	.	TON CO	TON H2	TON HCOOH	.
1.	Ru(dppq)(tpy)(MeCN)	0.02	BIH	0.1	DMA				Xenon lamp (420 - 750)		73	1	8
2.	Ru(dppq)(tpy)(MeCN)	0.04	BIH	0.1	DMA				Xenon lamp (420 - 750)		58	1	3
3.	Ru(dppq)(tpy)(MeCN)	0.08	BIH	0.1	DMA				Xenon lamp (420 - 750)		29		2
4.	Ru(dppq)(tpy)(MeCN)	0.04	BIH	0.1	MeCN				Xenon lamp (420 - 750)		42	1	5
5.	Ru(dppq)(tpy)(MeCN)	0.04	BIH	0.1	DMA				Xenon lamp (420 - 750)		67	1	9
6.	Ru(dppq)(tpy)(MeCN)	0.04	BIH	0.1	DMA				Xenon lamp (420 - 750)		20	1	6

Experiment-Name: Concentration and solvent effectExport

	cat	cat conc [µM]	e-D	e-D conc [M]	solvent A	.	.	additives	.	λexc [nm]	.	TON CO	.
1.	Ru(dppq)(tpy)(MeCN)	0.04	BIH	0.1	DMA					Xenon lamp (420 - 750)		4.6
2.	Ru(dppq)(tpy)(MeCN)	0.04	BIH	0.1	DMA			Hg(0)		Xenon lamp (420 - 750)		4.1

Experiment-Name: Hg poisoningExport

	cat	cat conc [µM]	e-D	e-D conc [M]	solvent A	.	.	.	λexc [nm]	.	TON CO	.
1.	Ru(dppq)(tpy)(MeCN)	0.04	BIH	0.1	DMA				Xenon lamp (420 - 750)		1.2
2.	Ru(dppq)(tpy)(MeCN)	0.04	BIH	0.1	DMA				Xenon lamp (420 - 750)		4.6

Experiment-Name: Presence of water effectExport

	cat	cat conc [µM]	e-D	e-D conc [M]	solvent A	.	.	.	λexc [nm]	.	TON CO	.	.
1.	Ru(dppq)(tpy)(MeCN)	0.005	BIH	0.2	DMA				Xenon lamp (420 - 750)		353

Experiment-Name: Maximum TONExport

Sacrificial electron donor

In this study, the experiments were done with the sacrificial electron donors TEOA (100507) and BIH (100508).

Additives

In this study, the addition of Hg(0) was tested and control experiments under argon atmosphere were conducted.