Unlocking full and fast conversion in photocatalytic carbon dioxide reduction for applications in radio-carbonylation

Harvesting sunlight to drive carbon dioxide (CO2) valorisation represents an ideal concept to support a sustainable and carbon-neutral economy. While the photochemical reduction of CO2 to carbon monoxide (CO) has emerged as a hot research topic, the full CO2-to-CO conversion remains an often-overlooked criterion that prevents a productive and direct valorisation of CO into high-value-added chemicals. Herein, we report a photocatalytic process that unlocks full and fast CO2-to-CO conversion (<10 min) and its straightforward valorisation into human health related field of radiochemistry with carbon isotopes. Guided by reaction-model-based kinetic simulations to rationalize reaction optimisations, this manifold opens new opportunities for the direct access to 11C- and 14C-labeled pharmaceuticals from their primary isotopic sources [11C]CO2 and [14C]CO2

Stratégies bio-inspirées pour la réduction catalytique et la valorisation du dioxyde de carbone

The criticality of global warming urges for the advancement of science to reduce carbon dioxide (CO₂) emissions in the atmosphere. At the heart of this challenge is the development of sustainable catalysts that can help capture, activate, reduce, and eventually valorize CO₂. This PhD work tried to respond to this call by developing molecular mimics inspired by natural systems in the larger scheme of artificial photosynthesis. Firstly, it involved tracking the journey of a photon of visible light and how it is transformed to a reducing power able to reduce CO₂. Secondly, in search for more efficient and stable catalysts, new mimics were synthesized inspired by the exceptional performance of CO dehydrogenase enzymes (CODH) in reducing CO₂. Lastly, further understanding of CODH also led to a proof-of-concept that directly valorizes the photo-produced CO for the synthesis of isotopically-labelled amide bonds, a common motif in pharmaceutically-relevant drugs.La criticité du réchauffement climatique incite à chercher des solutions pour réduire les émissions de dioxyde de carbone (CO₂). Le développement de catalyseurs qui peuvent aider à capturer, activer, réduire et valoriser le CO₂ est au cœur de ce défi. Cette thèse a répondu à cet appel en développant des mimétismes moléculaires inspirés de la Nature, dans le cadre plus large de la photosynthèse artificielle. Au début il s'agissait de suivre le parcours d'un photon de lumière visible et de déterminer comment il peut réduire la molécule de CO₂. Ensuite afin de réaliser des catalyseurs plus efficaces, de nouvelles molécules ont été synthétisées en s’inspirant de l’enzyme CO déshydrogénase (CODH) qui présente des performances exceptionnelles pour la réduction du CO₂. Enfin, une autre propriété du CODH a conduit à une validation de principe pour la valorisation immédiate du CO photo-produit dans la synthèse des liaisons amides marqués, une caractéristique courante des médicaments

Bio-inspired strategies for the catalytic reduction and valorization of carbon dioxide

La criticité du réchauffement climatique incite à chercher des solutions pour réduire les émissions de dioxyde de carbone (CO₂). Le développement de catalyseurs qui peuvent aider à capturer, activer, réduire et valoriser le CO₂ est au cœur de ce défi. Cette thèse a répondu à cet appel en développant des mimétismes moléculaires inspirés de la Nature, dans le cadre plus large de la photosynthèse artificielle. Au début il s'agissait de suivre le parcours d'un photon de lumière visible et de déterminer comment il peut réduire la molécule de CO₂. Ensuite afin de réaliser des catalyseurs plus efficaces, de nouvelles molécules ont été synthétisées en s’inspirant de l’enzyme CO déshydrogénase (CODH) qui présente des performances exceptionnelles pour la réduction du CO₂. Enfin, une autre propriété du CODH a conduit à une validation de principe pour la valorisation immédiate du CO photo-produit dans la synthèse des liaisons amides marqués, une caractéristique courante des médicaments.The criticality of global warming urges for the advancement of science to reduce carbon dioxide (CO₂) emissions in the atmosphere. At the heart of this challenge is the development of sustainable catalysts that can help capture, activate, reduce, and eventually valorize CO₂. This PhD work tried to respond to this call by developing molecular mimics inspired by natural systems in the larger scheme of artificial photosynthesis. Firstly, it involved tracking the journey of a photon of visible light and how it is transformed to a reducing power able to reduce CO₂. Secondly, in search for more efficient and stable catalysts, new mimics were synthesized inspired by the exceptional performance of CO dehydrogenase enzymes (CODH) in reducing CO₂. Lastly, further understanding of CODH also led to a proof-of-concept that directly valorizes the photo-produced CO for the synthesis of isotopically-labelled amide bonds, a common motif in pharmaceutically-relevant drugs

Recent advances in metalloporphyrin-based catalyst design towards carbon dioxide reduction: from bio-inspired second coordination sphere modifications to hierarchical architectures

International audienceResearch in the development of new molecular catalysts for the selective transformation of CO2 to reduced forms of carbon is attracting enormous interest from chemists. Molecular catalyst design hinges on the elaboration of ligand scaffolds to manipulate the electronic and structural properties for the fine tuning of the reactivity pattern. A cornucopia of ligand sets have been designed along this line and more and more are being reported. In this quest, the porphyrin molecular platform has been under intensive focus due to the unmatched catalytic properties of metalloporphyrins. There have been rapid advances in this particular field during the last few years wherein both electronic and structural aspects in the second coordination spheres have been addressed to shift the overpotential and improve the catalytic rates and product selectivity. Metalloporphyrins have also attracted much attention in terms of the elaboration of hybrid materials for heterogeneous catalysis. Here too, some promising activities have made metalloporphyrin derivatives serious candidates for technological implementation. This review collects the recent advances centred around the chemistry of metalloporphyrins for the reduction of CO2

Bimetallic Molecular Catalyst Design for Carbon Dioxide Reduction

The core challenge in developing cost-efficient catalysts for carbon dioxide (CO2) conversion mainly lies in controlling its complex reaction pathways. One such strategy exploits bimetallic cooperativity, which relies on the synergistic interaction between two metal centers to activate and convert the CO2 substrate. While this approach has seen an important trend in heterogeneous catalysis as a handle to control stabilities of surface intermediates, it has not often been utilized in molecular and heterogenized molecular catalytic systems. In this review, we gather general principles on how natural CO2 activating enzymes take advantage of bimetallic strategy and how phosphines, cyclams, polypyridyls, porphyrins, and cryptates-based homo-and hetero-bimetallic molecular catalysts can help understand the synergistic effect of two metal centers

Shaping the Electrocatalytic Performance of Metal Complexes for CO2 Reduction

International audienceThe mass scale catalytic transformation of carbon dioxide (CO2) into reduced forms of carbon is an imperative to address the ever-increasing anthropogenic emission. Understanding the mechanistic routes leading to the multi-electron-proton conversion of CO2 provides handles for chemists to overcome the kinetically and thermodynamically hard challenges and further optimize these processes. Through extensive electrochemical investigations, Prof. J-M. Savéant and coworkers have made accessible to chemists invaluable electro-analytical tools to address and position the electrocatalytic performance of molecular catalysts grounded on a theoretical basis. Furthermore, he has bequeathed lessons to future generations on ways to improve the catalytic activity and on the electrocatalytic zone we must target. As a tribute to his accomplishments, we recall here a few aspects on the tuning of iron porphyrin catalysts by playing on electronic effects, proton delivery, hydrogen bonding and electrostatic interactions and its implications to other catalytic systems

Through‐Space Electrostatic Interactions Surpass Classical Through‐Bond Electronic Effects in Enhancing CO 2 Reduction Performance of Iron Porphyrins

International audienceIn his pioneering work to unravel the catalytic power of enzymes, A. Warshel has pertinently validated that electrostatic interactions play a major role in the activation (bond making and breaking) of substrates. Implementing such chemical artifice in bio-inspired molecular-based catalysts may help in improving their catalytic properties. In this study, we have designed a series of tetra-, di-and mono-substituted iron porphyrins with cationic imidazolium functions. The presence of a cationic module in the second coordination sphere could help to stabilize the [Fe-CO2] intermediate upon electrocatalysis through an electrostatic interaction. We found herein that the overpotential of these catalysts is a function of the number of embarked imidazolium units ranging from 230 to 620 mV compared to 680 mV for the parent nonfunctionalized tetra-phenyl iron porphyrin. Importantly, we evidenced a gain of six orders of magnitude for the turnover frequencies going from the tetra-to the mono-substituted catalyst. The comparative study nails the fact that the electrocatalytic performance trend of through-space electrostatic interaction models outperforms the classic throughstructure electronic effect strategy. Henceforth, including controlled topological electrostatic interaction may be an invaluable chemical tool in the design of molecular catalysts in the activation of small molecules

Local ionic liquid environment at a modified iron porphyrin catalyst enhances the electrocatalytic performance of CO2 to CO reduction in water

International audienceIn this study we report a strategy to attach methylimidazolium fragments as ionic liquid units on an established iron porphyrin catalyst for the selective reduction of CO2 to CO. Importantly, we found that the tetra-methylimidazolium containing porphyrin exhibits an exalted electrocatalytic activity at low overpotential in water precluding the need for an external proton donor