نبذة مختصرة : International audience ; Light-dependent reduction of carbon dioxide (CO 2 ) 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 photoreduction of CO 2 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 -1 , a turnover value of ~ 589, after 3 h reaction, and a CO vs H 2 selectivity of 72 % were obtained, establishing a record among previously reported artificial CO 2 reductases. Thorough photophysical studies allowed tracking reaction intermediates and provided insights into the reaction mechanism. Thanks to a high-resolution crystal structure of the artificial enzyme, both in the absence and in the presence of the protein-bound CO 2 substrate, a rational sitedirected mutagenesis approach was used to study the effect of some modifications of the active site on the activity.
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