Molecular Catalysis of the Electrochemical and Photochemical Reduction of CO2 with Earth-Abundant Metal Complexes. Selective Production of CO vs HCOOH by Switching of the Metal Center

Abstract

Summary

A photochemical reduction of CO₂ to CO or formic acid was shown using the iron complex [Fe(pabop)Cl2][CLO4] (100755) or the cobalt complex [Co(pabop)][ClO4]2 (100759) as catalysts in combination with the iridium-based photosensitizer Ir(ppy)3 (100843). Turnover numbers (TONs) of 270 for CO with the cobalt complex and 5 for formic acid with the iron complex were reached in acetonitrile. The experiments were conducted under visible-light irradiation (λ > 460 nm) using TEA as sacrificial reductants (see section SEDs below).

Advances and special progress

The authors could demonstrate that switching the metal center has a major influence on the outcome of CO2 reduction, enabling the generation of either CO or formic acid depending on the employed metal.

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 iron or cobalt complexes as catalysts. The catalytic system performs best (referring to the TON of CO production) in acetonitrile with the cobalt catalyst.

Catalyst

[Fe(pabop)Cl2][CLO4] (100755) [Co(pabop)][ClO4]2 (100759)

Photosensitizer

Ir(ppy)3 (100843)

Investigation

		cat	cat conc [µM]	PS	PS conc [mM]	e-D	solvent A	.	.	λexc [nm]	.	TON CO	TON HCOOH	.	.
(edit)	1.	[Co(pabop)][ClO4]2	0.05	Ir(ppy)3	0.2	TEA	MeCN			>460		270
(edit)	2.	[Fe(pabop)Cl2][CLO4]	0.05	Ir(ppy)3	0.2	TEA	MeCN			>420			5

Investigation-Name: Table 1

Sacrificial electron donor

In this study, the experiments were done with the sacrificial electron donor TEA (100505).

Additives

In this study, no additives were tested.