Light-Activated Artificial CO-Reductase: Structure and Activity.

Light-dependent reduction of carbon dioxide (CO) into value-added products can be catalyzed by a variety of molecular complexes. Here we report a rare example of a structurally characterized artificial enzyme, resulting from the combination of a heme binding protein, heme oxygenase, with cobalt-protoporphyrin IX, with good activity for the photoreduction of CO to carbon monoxide (CO). Using a copper-based photosensitizer, thus making the photosystem free of noble metals, a large turnover frequency value of ∼616 h, a turnover value of ∼589, after 3 h reaction, and a CO vs H selectivity of 72% were obtained, establishing a record among previously reported artificial CO reductases.

[4Fe-4S]-dependent enzymes in non-redox tRNA thiolation.

Post-transcriptional modification of nucleosides in transfer RNAs (tRNAs) is an important process for accurate and efficient translation of the genetic information during protein synthesis in all domains of life. In particular, specific enzymes catalyze the biosynthesis of sulfur-containing nucleosides, such as the derivatives of 2-thiouridine (sU), 4-thiouridine (sU), 2-thiocytidine (sC), and 2-methylthioadenosine (msA), within tRNAs. Whereas the mechanism that has prevailed for decades involved persulfide chemistry, more and more tRNA thiolation enzymes have now been shown to contain a [4Fe-4S] cluster.

An organic O donor for biological hydroxylation reactions.

All biological hydroxylation reactions are thought to derive the oxygen atom from one of three inorganic oxygen donors, O, HO or HO. Here, we have identified the organic compound prephenate as the oxygen donor for the three hydroxylation steps of the O-independent biosynthetic pathway of ubiquinone, a widely distributed lipid coenzyme. Prephenate is an intermediate in the aromatic amino acid pathway and genetic experiments showed that it is essential for ubiquinone biosynthesis in under anaerobic conditions.

Zr-Based MOF-545 Metal-Organic Framework Loaded with Highly Dispersed Small Size Ni Nanoparticles for CO Methanation.

We report the use of Zr-based metal-organic frameworks (MOFs) MOF-545 and MOF-545(Cu) as supports to prepare catalysts with uniformly and highly dispersed Ni nanoparticles (NPs) for CO hydrogenation into CH. In the first step, we studied the MOF support under catalytic conditions using operando diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, ex situ characterizations (PXRD, XPS, TEM, and EDX-element mapping), and DFT calculations. We showed that the high-temperature conditions undoubtedly confer a potential for catalytic functionality to the solids toward CH production, while no role of the Cu could be evidenced.

Smart Electrode Surfaces by Electrolyte Immobilization for Electrocatalytic CO Conversion.

The activity and selectivity of molecular catalysts for the electrochemical CO reduction reaction (CORR) are influenced by the induced electric field at the electrode/electrolyte interface. We present here a novel electrolyte immobilization method to control the electric field at this interface by positively charging the electrode surface with an imidazolium cation organic layer, which significantly favors CO conversion to formate, suppresses hydrogen evolution reaction, and diminishes the operating cell voltage. Those results are well supported by our previous DFT calculations studying the mechanistic role of imidazolium cations in solution for CO reduction to formate catalyzed by a model molecular catalyst.