Light-Driven Hydrogen Evolution Reaction Catalyzed by a Molybdenum–Copper Artificial Hydrogenase
Raphaël J. Labidi, Bruno Faivre, Philippe Carpentier, Giulia Veronesi, Albert Solé‐Daura, Ragnar Björnsson, Christophe Léger, Philipp Gotico, Yun Li, Mohamed Atta, Marc Fontecave
Abstract
Orange protein (Orp) is a small bacterial metalloprotein of unknown function that harbors a unique molybdenum/copper (Mo/Cu) heterometallic cluster, [S 2 MoS 2 CuS 2 MoS 2 ] 3– . In this paper, the performance of Orp as a catalyst for the photocatalytic reduction of protons into H 2 has been investigated under visible light irradiation. We report the complete biochemical and spectroscopic characterization of holo -Orp containing the [S 2 MoS 2 CuS 2 MoS 2 ] 3– cluster, with docking and molecular dynamics simulations suggesting a positively charged Arg, Lys-containing pocket as the binding site. Holo -Orp exhibits excellent photocatalytic activity, in the presence of ascorbate as the sacrificial electron donor and [Ru(bpy) 3 ]Cl 2 as the photosensitizer, for hydrogen evolution with a maximum turnover number of 890 after 4 h irradiation. Density functional theory (DFT) calculations were used to propose a consistent reaction mechanism in which the terminal sulfur atoms are playing a key role in promoting H 2 formation. A series of dinuclear [S 2 MS 2 M′S 2 MS 2 ] (4 n )– clusters, with M = Mo VI, W VI and M′ ( n +) = Cu I, Fe I, Ni I, Co I, Zn II, Cd II were assembled in Orp, leading to different M/M′-Orp versions which are shown to display catalytic activity, with the Mo/Fe-Orp catalyst giving a remarkable turnover number (TON) of 1150 after 2.5 h reaction and an initial turnover frequency (TOF°) of 800 h –1 establishing a record among previously reported artificial hydrogenases.