Institut de Chimie Moléculaire et des Matériaux d'Orsay

Iron porphyrins are among the most studied molecular catalysts for carbon dioxide (CO₂) reduction and their reactivity is constantly being enhanced through the implementation of chemical functionalities in the second coordination sphere inspired by the active sites of enzymes. In this study, we were intrigued to observe that a multipoint hydrogen bonding scheme provided by embarked urea groups could also shift the redox activation step of CO₂ from the well-admitted Fe(0) to the Fe(I) state. Using EPR, resonance Raman, IR and UV-Visible spectroscopies, we underpinned a two-electron activation step of CO₂ starting from the Fe(I) oxidation state to form, after protonation, an Fe(III)‒COOH species. The addition of another electron and a proton to the latter species converged to the cleavage of a C‒O bond with the loss of water molecule resulting in an Fe(II)‒CO species. The DFT analyses of these postulated intermediates is in good agreement with our collected spectroscopic data, thus allowing us to propose an alternative pathway in the catalytic CO₂ reduction with iron porphyrin catalyst. Such a remarkable shift opens new lines of research in the design of molecular catalysts to reach low overpotentials in performing multi-electronic CO₂ reduction catalysis.

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 

The development of efficient hydrogen production technologies is fundamental for global sustainability. As such, electrocatalysts derived from earth abundant metal complexes are appealing, and interesting performances have typically been disclosed under acidic conditions in organic solvents. However, their applicability under relevant pH neutral conditions is underexplored. Herein, we demonstrate that non-ionic, dimeric cobalt-dithiolene complexes supported on multi-wall carbon nanotubes (MWCNTs)/carbon paper (CP) electrode are powerful electrocatalysts for hydrogen production in aqueous media at pH 7. The high turnover numbers encountered (TON up to 50980) after long reaction times (up to 16 hours) are reasoned by the increased electro-active cobalt concentration on the modified electrode, which is ca. 4 times higher than that of a state-of-the-art cobalt porphyrin electrocatalyst. These findings point out that immobilizing well-defined, multinuclear low-cost metal complexes on carbon material is a promising strategy to design highly electroactive electrodes.

At the core of carbon monoxide dehydrogenase (CODH) active site two metal ions together with hydrogen bonding scheme from amino acids orchestrate the interconversion between CO₂ and CO. We have designed a molecular catalyst implementing a bimetallic iron complex with an embarked second coordination sphere with multi-point hydrogen-bonding interactions. We

Using light energy to drive multielectron catalytic reduction of CO₂ to produce a fuel is a contemporary research thrust. Recent efforts in the design of porphyrin-based catalysts have positioned them among the most performant electrocatalysts for CO₂ reduction. Powering these catalysts with the help of photosensitizers to realize light-driven catalysis comes along with a couple of

Intense efforts are currently being injected in discovering cost-effective catalysts for the selective reduction of carbon dioxide (CO₂). Much advances have indeed been realized in the design of molecular complexes containing second coordination chemical functionalities that have contributed to boost the homogeneous electrocatalytic activity. Implementing these chemical facets in heterogeneous catalysis can give access to an improved catalysis while opening at the same time the way for practical and sustainable applications. Here we report the catalytic properties for CO₂ electroreduction of a

In his pioneering work to unravel the catalytic power of enzymes, Warshel has pertinently validated that electrostatic interactions play a major role in the activation of substrates. Implementing such chemical artifice in molecular catalysts may help improve their catalytic properties. In this study, we have designed a series of tetra-, di- and mono-substituted iron porphyrins with cationic imidazolium groups. Their presence in the second coordination sphere help stabilize the [Fe-CO₂] intermediate through electrostatic interactions. We found herein that the electrocatalytic overpotential is a function of the number of embarked imidazolium. Importantly, we evidenced a gain of six orders of magnitude in turnover frequencies going from a tetra- to a mono-substituted catalyst. Furthermore, our comparative study shows that catalytic performances trend of through-space electrostatic interaction, a first topological effect reported for iron porphyrins, outperforms the classical through-structure electronic effect.

The manipulation of the second coordination sphere for improving the electrocatalytic CO₂ reduction has led to amazing breakthroughs with hydrogen bonding, local proton source, or electrostatic effects. We have developed two atropisomers of an iron porphyrin complex holding two urea functions acting as multiple hydrogen bonding tweezers to lock the metal bound CO₂ in a similar fashion found in the carbon monoxide dehydrogenase (CODH) enzyme. We found that the aa topological isomer with the two urea groups on the same side of the porphyrin platform provides a stronger binding affinity to tether

Research 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 has been designed along this line and more and more are being reported. In this quest, the

In 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.

Reduce, reuse, recycle: A CO₂ valorization strategy based on its photocatalytic reduction to CO and the direct use of the produced CO in a palladium‐catalyzed aminocarbonylation reaction is reported. This approach provides a means for more efficient application of ¹³C‐isotope and ¹⁴C‐radioisotope‐labeled CO₂ in pharmaceutically relevant drug labeling.