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.

Fused radical SAM and αKG-HExxH domain proteins contain a distinct structural fold and catalyse cyclophane formation and β-hydroxylation.

Two of nature's recurring binding motifs in metalloproteins are the CxxxCxxC motif in radical SAM enzymes and the 2-His-1-carboxylate motif found both in zincins and α-ketoglutarate and non-haem iron enzymes. Here we show the confluence of these two domains in a single post-translational modifying enzyme containing an N-terminal radical S-adenosylmethionine domain fused to a C-terminal 2-His-1-carboxylate (HExxH) domain. The radical SAM domain catalyses three-residue cyclophane formation and is the signature modification of triceptides, a class of ribosomally synthesized and post-translationally modified peptides.

Impact of the Surface Microenvironment on the Redox Properties of a Co-Based Molecular Cathode for Selective Aqueous Electrochemical CO-to-CO Reduction.

Electrode-confined molecular catalysts are promising systems to enable the efficient conversion of CO to useful products. Here, we describe the development of an original molecular cathode for CO reduction to CO based on the noncovalent integration of a tetraazamacrocyclic Co complex to a carbon nanotube-based matrix. Aqueous electrochemical characterization of the modified electrode allowed for clear observation of a change of redox behavior of the Co center as surface concentration was tuned, highlighting the impact of the catalyst microenvironment on its redox properties.

Synthetic styrene-based bioinspired model of the [FeFe]-hydrogenase active site for electrocatalytic hydrogen evolution.

Integration of molecular catalysts inside polymeric scaffolds has gained substantial attention over the past decade, as it provides a path towards generating systems with enhanced stability as well as enzyme-like morphologies and properties. In the context of solar fuels research and chemical energy conversion, this approach has been found to improve both rates and energy efficiencies of a range of catalytic reactions. However, system performance still needs to be improved to reach technologically relevant currents and stability, parameters that are heavily influenced by the nature of the incorporated molecular catalyst.