Promoting photocatalytic CO2 reduction with a molecular copper purpurin chromophore

Abstract

Summary

A photochemical reduction of CO₂ to CO was shown using the iron porphyrin Fe(DHPP)Cl as catalyst in combination with the copper purpurin photosensitizer [Cu(PP)2][TBA]2. Turnover numbers (TONs) over 16100 and a selectivity of 95% for CO were reached in DMF. The experiments were conducted under visible-light irradiation (λ > 400 nm) using BIH as sacrificial electron donor (see section SEDs below).

Advances and special progress

The authors designed an efficient photosensitizer for CO₂ reduction via the connection of a redox-active metal center to a natural organic dye. The reported turnover number is among the highest known for homogenous and noble metal-free systems and its efficiency is comparable to highly active noble metal-based systems.

Additional remarks

Two different pathways for the photocatalytic CO₂ reduction depending on the concentration of BIH are proposed.

Content of the published article in detail

The article contains results for the reduction of CO₂ to CO under visible-light catalysis using an iron complex as a catalyst. The catalytic system performs best (referring to the TON of CO production) in DMF.

Catalyst

Fe(DHPP)Cl

Photosensitizer

[Cu(PP)2][TBA]2 purpurin

Investigation

	cat	cat conc [µM]	PS	PS conc [mM]	e-D	e-D conc [M]	solvent A	λexc [nm]	.	TON CO	.	TON H2	.
1.	Fe(DHPP)Cl	0.0002	purpurin	0.1	BIH	0.01	DMF	>400		88		0
2.	Fe(DHPP)Cl	0.0002	[Cu(PP)2][TBA]2	0.1	BIH	0.01	DMF	>400		4779		270
3.	Fe(DHPP)Cl	0.0002	[Cu(PP)2][TBA]2	0.1	BIH	0.1	DMF	>400		16109		843
4.	Fe(DHPP)Cl	0	[Cu(PP)2][TBA]2	0.1	BIH	0.1	DMF	>400		4.4		0

Experiment-Name: Photocatalytic CO2 reduction: best resultsExport

	cat	cat conc [µM]	PS	PS conc [mM]	e-D	e-D conc [M]	solvent A	additives	.	.	λexc [nm]	.	TON CO	TON H2	.
1.	[MoO(2Hqpdt)2][NBu4]	0.0001	[Cu(PP)2][TBA]2	0.1	BIH	0.1	DMF				white LED		8600	144
2.			[Cu(PP)2][TBA]2	0.1	BIH	0.1	DMF				white LED		0	0
3.	[MoO(2Hqpdt)2][NBu4]	0.0001			BIH	0.1	DMF				white LED		0	0
4.	[MoO(2Hqpdt)2][NBu4]	0.0001	[Cu(PP)2][TBA]2	0.1	BIH	0.1	DMF				white LED		0	1466
5.	[MoO(2Hqpdt)2][NBu4]	0.0001	[Cu(PP)2][TBA]2	0.1	BIH	0.1	DMF						0	0
6.	[MoO(2Hqpdt)2][NBu4]	0.0001	[Cu(PP)2][TBA]2	0.1			DMF				white LED		0	0
7.	[MoO(2Hqpdt)2][NBu4]	0.00002	[Cu(PP)2][TBA]2	0.1	BIH	0.1	DMF				white LED		16109	843
8.	[MoO(2Hqpdt)2][NBu4]	0.0002	[Cu(PP)2][TBA]2	0.1	BIH	0.1	DMF				white LED		5963	63
9.	[MoO(2Hqpdt)2][NBu4]	0.0001	[Cu(PP)2][TBA]2	0.1	BIH	0.1	DMF	Hg			white LED		8600	144
10.	[MoO(2Hqpdt)2][NBu4]	0.0005	[Cu(PP)2][TBA]2	0.1	BIH	0.1	DMF				white LED		3385	43
11.	[MoO(2Hqpdt)2][NBu4]	0.001	[Cu(PP)2][TBA]2	0.1	BIH	0.1	DMF				white LED		3131	12

Experiment-Name: Control experimentsExport

Sacrificial electron donor

In this study, the experiments were done with the sacrificial electron donor BIH (100508).

Additives

In this study, control experiments with Hg were conducted.