Abstract
The current trend in atmospheric carbon dioxide concentrations is causing increasing concerns for its environmental impacts, and spurring the developments of sustainable methods to reduce CO2 to usable molecules. We report the light-driven CO2 reduction in water in mild conditions by artificial protein catalysts based on cytochrome b 562 and incorporating cobalt protoporphyrin IX as cofactor. Incorporation into the protein scaffolds enhances the intrinsic reactivity of the cobalt porphyrin toward proton reduction and CO generation. Mutations around the binding site modulate the activity of the enzyme, pointing to the possibility of further improving catalytic activity through rational design or directed evolution.
Highlights
The ongoing use of fossil fuels has led to an increase in atmospheric CO2 concentrations, causing severe consequences for the environment (Lacis et al, 2010)
We have investigated the effect of the primary coordination sphere provided by the protein environment of cobalt cytochrome b562 in the light-promoted CO2 reduction pathway in mild aqueous conditions
Our results indicate that the native CO2 reduction activity of cobalt protoporphyrin IX (CoPPIX) is increased when incorporated into the protein, whereas HCO2− production is not affected by the protein scaffold
Summary
The ongoing use of fossil fuels has led to an increase in atmospheric CO2 concentrations, causing severe consequences for the environment (Lacis et al, 2010). Protein scaffolds may aide the efficiency of the organometallic center by offering tunable primary and secondary coordination spheres, by facilitating reactant binding and product release to and from the active site, and by protecting the organometallic center from degradation (Lu et al, 2009; AlcalaTorano et al, 2016; Schwizer et al, 2018; Davis and Ward, 2019; Nastri et al, 2019; Oohora et al, 2019; Vornholt et al, 2020) This approach has been used to produce water-soluble catalysts that are capable of producing hydrogen from protons under mild conditions, repurposing a diverse group of organometallic catalysts (Sano et al, 2011; Roy et al, 2012; Kleingardner et al, 2014; Onoda et al, 2014; Sommer et al, 2014; Sommer et al, 2016; Firpo et al, 2018; Call et al, 2019a; Slater et al, 2019; Walsh et al, 2019; Alvarez-Hernandez et al, 2020; Laureanti et al, 2020; Le et al, 2020; Roy et al, 2020). Little work has been carried out on the reduction of CO2 by hybrid metalloenzymes: in one example nickel cyclam complexes anchored to azurin support catalytic CO2 reduction, with evidence of protein
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