Homogeneous Systems Containing Earth‐Abundant Metal Complexes for Photoactivated CO₂ Reduction: Recent Advances

Abstract

Photo-driven reduction of CO 2 into advantageous chemicals is a noteworthy pathway to close the carbon cycle and decrease carbon footprint. The use of visible light and ultimately solar radiation is extremely interesting in managing energy issues. Similarly, the employment of cost-effective materials guides to environmentally friendly applications. This Review addresses the homogeneous systems used for photoactivated the CO 2 reduction in the last years, highlighting the earth-abundant metal-based components. Besides those systems composed only of noble metal-free units, hybrid systems, also containing a noble metal-based complex, are also examined, revealing that research needs to increase the attention on more sustainable alternatives.

Bioinspired motifs in proton and CO2 reduction with 3d-metal polypyridine complexes

“…These studies require the combination of a molecular catalyst (Cat) with a light-harvesting photosensitizer (PS) and an electron donor (ED). 12,29,30 Under irradiation conditions, excitation of the PS is followed by reductive electron transfer quenching of the excited state PS* by the ED, leading to the formation of the reduced PS − species. This latter then undergoes electron transfer to the catalyst, either in its pristine (Cat) or one-electron reduced (Cat − ) form (Fig.…”

Fusion Position-Dependent Aromatic Transitions of Ligand Backbone Rings for Controlling the Redox Energetics of Photoredox Catalysts

“…There is an ongoing demand for ever stronger photooxidants and photoreductants, especially with the aim to develop effective photoredox catalysts for intricate processes like smallmolecule activation (e.g., CO 2 , NO 3 − , and N 2 ). 26,27 Understanding the mechanisms and factors that influence the redox properties of photoredox catalysts is vital to establishing design principles for adjusting the reactivity while meeting the demands for greener synthetic protocols. 23,28 Modifying the metal center, 21,29 counterions, 30 and ligands 2131,32 are known mechanisms for tuning the reduction potentials of transition metal complexes.…”

“…There is an ongoing demand for ever stronger photooxidants and photoreductants, especially with the aim to develop effective photoredox catalysts for intricate processes like small-molecule activation (e.g., CO 2 , NO 3 – , and N 2 ). , Understanding the mechanisms and factors that influence the redox properties of photoredox catalysts is vital to establishing design principles for adjusting the reactivity while meeting the demands for greener synthetic protocols. , Modifying the metal center, , counterions, and ligands , are known mechanisms for tuning the reduction potentials of transition metal complexes. For this, it is important to understand that the four electron transfer events of the oxidative and reductive quenching cycles (shown in Figure ) can be characterized as formally metal- ( D ox → S 0 and T 1 → D red ) and ligand-centered ( S 0 → D red and D ox → T 1 ) redox processes. , Particularly, in the latter, the intrinsic properties of the redox-active ligands profoundly impact the thermodynamics of the electron transfer event.…”

Photocatalytic CO2 Reduction Using Mixed Catalytic Systems Comprising an Iron Cation with Bulky Phenanthroline Ligands

“…Catalytic reactions utilizing earth-abundant metals as catalysts are crucial in terms of the expansion of metal resources. As 3d metals, such as Cu and Fe, are more abundant than central metal ions of well-known efficient catalysts, such as Ru, Rh, and Pd (4d metals) and Pt (5d metal), the utilization of 3d metal elements as catalysts is attracting widespread research attention . However, 3d metals tend to lose their original structure owing to oxidation and/or ligand dissociation, which are generally the main reasons for their efficient catalytic functions being difficult.…”