Photocatalytic CO2 Reduction Using a Robust Multifunctional Iridium Complex toward the Selective Formation of Formic Acid

Abstract

Summary

A photochemical reduction of CO₂ to formic acid and CO was shown using the iridium complex [Ir(mesbpy-(PCy2)2)][BPh4] as a catalyst without any additional photosensitizer. Turnover numbers (TONs) of 2080 and a selectivity of 87% for formic acid were reached in dimethylacetamide/water. 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 have developed a multifunctional catalyst that allows for selective generation of formic acid without the need for an external photosensitizer.

Additional remarks

The developed catalyst reduces CO2 to CO via inner-sphere catalysis and to formic acid via outer-sphere catalysis.

Content of the published article in detail

The article contains results for the reduction of CO₂ to CO and formic acid under visible-light catalysis using an iridium complex. The catalytic system performs best (referring to the TON of formic acid production) in dimethylacetamide/water.

Catalyst

[Ir(mesbpy-(PCy2)2)][BPh4]

Investigation

	cat	cat conc [µM]	e-D	e-D conc [M]	solvent A	.	.	λexc [nm]	.	TON CO	TON H2	TON HCOOH	.
1.	[Ir(mesbpy-(PCy2)2)][BPh4]	0.02	BIH	0.2	DMA			>400		470	15	2080

Investigation-Name: Photocatalytic reduction of CO2, best TONExport

	cat	cat conc [µM]	solvent A	.	.	.	additives	.	.	.	λexc [nm]	.	TON CO	TON H2	TON HCOOH	.
1.	[Ir(mesbpy-(PCy2)2)][BPh4]	0.02	DMA				Hg				>400		69	0.9	291
2.	[Ir(mesbpy-(PCy2)2)][BPh4]	0.02	DMA								>400		62	0.8	323
3.	[Ir(mesbpy-(PCy2)2)][BPh4]	0.02	DMA								>400		3.9	0.9	188
4.	[Ir(mesbpy-(PCy2)2)][BPh4]	0.02	DMA								>400		57	5	115

Investigation-Name: Control experimentsExport

Sacrificial Electron Donor

In this study, the experiments were done with the sacrificial electron donor BIH (BIH), water (H2O) and triethanolamine (TEOA).

Additives

In this study, additional control experiments were conducted with Hg.