Dissection of Light‐Induced Charge Accumulation at a Highly Active Iron Porphyrin: Insights in the Photocatalytic CO<sub>2</sub> Reduction

Pugliese, Eva; Gotico, Philipp; Wehrung, Iris; Boitrel, Bernard; Quaranta, Annamaria; Ha‐Thi, Minh‐Huong; Pino, T.; Sircoglou, Marie; Leibl, Winfried; Halime, Zakaria; Aukauloo, Ally

doi:10.1002/ange.202117530

Cited by 10 publications

(3 citation statements)

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“…In such a CO 2 reduction system, the catalyst is reduced after gaining electrons from the oxidative/reductive quenching process of the excited photosensitizer to generate the catalytically active species. Apart from the noble metal complexes (i.e., Re, − Ru, − Rh, and Ir complexes − ), many non-noble transition metal complexes, such as Mn, − Fe, − Co, − Ni, − and Cu complexes, − have also been used in photochemical CO 2 reduction. Modifying the ligands from neutral to charged groups can stabilize the critical M–CO 2 and M–CO intermediates through noncovalent electrostatic interactions, thus promoting the CO 2 RR toward target products.…”

Section: Introductionmentioning

confidence: 99%

Mechanistic Insights into Photochemical CO₂ Reduction to CH₄ by a Molecular Iron–Porphyrin Catalyst

Chen

Liao

2023

Inorg. Chem.

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Iron tetraphenylporphyrin complex modified with four trimethylammonium groups (Fe-p-TMA) is found to be capable of catalyzing the eight-electron eight-proton reduction of CO2 to CH4 photochemically in acetonitrile. In the present work, density functional theory (DFT) calculations have been performed to investigate the reaction mechanism and to rationalize the product selectivity. Our results revealed that the initial catalyst Fe-p-TMA ([Cl–Fe(III)-LR4]4+, where L = tetraphenylporphyrin ligand with a total charge of −2, and R4 = four trimethylammonium groups with a total charge of +4) undergoes three reduction steps, accompanied by the dissociation of the chloride ion to form [Fe(II)-L••2–R4]2+. [Fe(II)-L••2–R4]2+, bearing a Fe(II) center ferromagnetically coupled with a tetraphenylporphyrin diradical, performs a nucleophilic attack on CO2 to produce the 1η-CO2 adduct [CO2 •––Fe(II)-L•–R4]2+. Two intermolecular proton transfer steps then take place at the CO2 moiety of [CO2 •––Fe(II)-L•–R4]2+, resulting in the cleavage of the C–O bond and the formation of the critical intermediate [Fe(II)–CO]4+ after releasing a water molecule. Subsequently, [Fe(II)–CO]4+ accepts three electrons and one proton to generate [CHO–Fe(II)-L•–R4]2+, which finally undergoes a successive four-electron-five-proton reduction to produce methane without forming formaldehyde, methanol, or formate. Notably, the redox non-innocent tetraphenylporphyrin ligand was found to play an important role in CO2 reduction since it could accept and transfer electron(s) during catalysis, thus keeping the ferrous ion at a relatively high oxidation state. Hydrogen evolution reaction via the formation of Fe-hydride ([Fe(II)–H]3+) turns out to endure a higher total barrier than the CO2 reduction reaction, therefore providing a reasonable explanation for the origin of the product selectivity.

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Section: Introductionmentioning

confidence: 99%

Mechanistic Insights into Photochemical CO₂ Reduction to CH₄ by a Molecular Iron–Porphyrin Catalyst

Chen

Liao

2023

Inorg. Chem.

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“…The typical metal–ligand synergistic effects to boost CO 2 RR involve H-bonding, proton shuttle, electrostatic interaction, and electron relay (Figure ). The catalysts with active-proton groups, including amide, urea, guanidine, imidazolium, and triazole, can form intramolecular H-bonding and considerably stabilize the metal-carboxylate or metal-carboxylic acid intermediates (Figure a). Such an interaction equals to a 5–15 kcal mol –1 decline of the chemical potential, leading to the gain of the order of magnitude in the turnover frequency .…”

Section: Introductionmentioning

confidence: 99%

Ligand-Bound CO₂ as a Nonclassical Route toward Efficient Photocatalytic CO₂ Reduction with a Ni N-Confused Porphyrin

Yuan,

Krishna,

Wei

et al. 2024

J. Am. Chem. Soc.

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Implementing the synergistic effects between the metal and the ligand has successfully streamlined the energetics for CO 2 activation and gained high catalytic activities, establishing the important breakthroughs in photocatalytic CO 2 reduction. Herein, we describe a Ni(II) N-confused porphyrin complex (NiNCP) featuring an acidic N− H group. It is readily deprotonated and exists in an anion form during catalysis. Owing to this functional site, NiNCP gave rise to an outstanding turnover number (TON) as high as 217,000 with a 98% selectivity for CO 2 reduction to CO, while the parent Ni(II) porphyrin (NiTPP) was found to be nearly inactive. Our mechanistic analysis revealed a nonclassical reaction pattern where CO 2 was effectively activated via the attack of the Lewis-basic ligand. The resulting ligandbound CO 2 adduct could be further reduced to produce CO. This new metal−ligand synergistic effect is anticipated to inspire the design of highly active catalysts for small molecule activations.

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“…Immobilization of the metal complex photocatalysts on solid substrates is an important technique for the easy separation of CO 2 -reduction products. Immobilization of CO 2 -reduction catalysts without the loss of activity and structure analyses of the immobilized catalysts are significant topics in the field of material synthesis and catalyst engineering based on inorganic chemistry. − Metalloporphyrins, a representative CO 2 -reduction photocatalyst, have been immobilized using substrates such as carbon nitride, mesoporous silica, and porous organic polymers. − The activity of immobilized metalloporphyrins is moderate due to the unexpected light scattering and absorption by the substrate materials because the substrates are dispersed in CO 2 -saturated solutions for photoirradiation. − Another reason for the moderate activity is that metalloporphyrins immobilized in the deep subsurface of the substrates hardly absorb light. These problems can be solved by immobilizing the metalloporphyrins in transparent and grain boundary-free membrane substrates with a wide illuminated surface area, but the membranes with these features are not fabricated using conventional substrate materials.…”

Section: Introductionmentioning

confidence: 99%

Heterogenous CO₂ Reduction Photocatalysis of Transparent Coordination Polymer Glass Membranes Containing Metalloporphyrins

et al. 2023

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Transparent and grain boundary-free substrates are essential to immobilize molecular photocatalysts for efficient photoirradiation reactions without unexpected light scattering and absorption by the substrates. Herein, membranes of coordination polymer glass immobilizing metalloporphyrins were examined as a heterogeneous photocatalyst for carbon dioxide (CO 2 ) reduction under visible-light irradiation. [Zn(HPO 4 )-(H 2 PO 4 ) 2 ](ImH 2 ) 2 (Im = imidazolate) liquid containing iron(III) 5,10,15,20-tetraphenyl-21H,23H-porphine chloride (Fe(TPP)Cl, 0.1-0.5 w/w%) was cast on a borosilicate glass substrate, followed by cooling to room temperature, resulting in transparent and grain boundary-free membranes with the thicknesses of 3, 5, and 9 μm. The photocatalytic activity of the membranes was in proportion to the membrane thickness, indicating that Fe(TPP)Cl in the subsurface of membranes effectively absorbed light and contributed to the reactions. The membrane photocatalysts were intact during the photocatalytic reaction and showed no recrystallization or leaching of Fe(TPP)Cl.

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Dissection of Light‐Induced Charge Accumulation at a Highly Active Iron Porphyrin: Insights in the Photocatalytic CO₂ Reduction

Abstract: Scheme 2. Proposed mechanism for the light-induced CO 2 reduction to CO with UrFe with the species characterized.

Cited by 10 publications

References 54 publications

Mechanistic Insights into Photochemical CO₂ Reduction to CH₄ by a Molecular Iron–Porphyrin Catalyst

Mechanistic Insights into Photochemical CO₂ Reduction to CH₄ by a Molecular Iron–Porphyrin Catalyst

Ligand-Bound CO₂ as a Nonclassical Route toward Efficient Photocatalytic CO₂ Reduction with a Ni N-Confused Porphyrin

Heterogenous CO₂ Reduction Photocatalysis of Transparent Coordination Polymer Glass Membranes Containing Metalloporphyrins

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Dissection of Light‐Induced Charge Accumulation at a Highly Active Iron Porphyrin: Insights in the Photocatalytic CO2 Reduction

Abstract: Scheme 2. Proposed mechanism for the light-induced CO 2 reduction to CO with UrFe with the species characterized.

Cited by 10 publications

References 54 publications

Mechanistic Insights into Photochemical CO2 Reduction to CH4 by a Molecular Iron–Porphyrin Catalyst

Mechanistic Insights into Photochemical CO2 Reduction to CH4 by a Molecular Iron–Porphyrin Catalyst

Ligand-Bound CO2 as a Nonclassical Route toward Efficient Photocatalytic CO2 Reduction with a Ni N-Confused Porphyrin

Heterogenous CO2 Reduction Photocatalysis of Transparent Coordination Polymer Glass Membranes Containing Metalloporphyrins

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Dissection of Light‐Induced Charge Accumulation at a Highly Active Iron Porphyrin: Insights in the Photocatalytic CO₂ Reduction

Mechanistic Insights into Photochemical CO₂ Reduction to CH₄ by a Molecular Iron–Porphyrin Catalyst

Mechanistic Insights into Photochemical CO₂ Reduction to CH₄ by a Molecular Iron–Porphyrin Catalyst

Ligand-Bound CO₂ as a Nonclassical Route toward Efficient Photocatalytic CO₂ Reduction with a Ni N-Confused Porphyrin

Heterogenous CO₂ Reduction Photocatalysis of Transparent Coordination Polymer Glass Membranes Containing Metalloporphyrins