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A photosensitizer–polyoxometalate dyad that enables the decoupling of light and dark reactions for delayed on-demand solar hydrogen production

Abstract

Decoupling the production of solar hydrogen from the diurnal cycle is a key challenge in solar energy conversion, the success of which could lead to sustainable energy schemes capable of delivering H2 independent of the time of day. Here, we report a fully integrated photochemical molecular dyad composed of a ruthenium-complex photosensitizer covalently linked to a Dawson polyoxometalate that acts as an electron-storage site and hydrogen-evolving catalyst. Visible-light irradiation of the system in solution leads to charge separation and electron storage on the polyoxometalate, effectively resulting in a liquid fuel. In contrast to related, earlier dyads, this system enables the harvesting, storage and delayed release of solar energy. On-demand hydrogen release is possible by adding a proton donor to the dyad solution. The system is a minimal molecular model for artificial photosynthesis and enables the spatial and temporal separation of light absorption, fuel storage and hydrogen release.

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Fig. 1: Schematic illustration of the coupled light and dark reaction.
Fig. 2: Synthesis and spectroscopic properties of PS-POM.
Fig. 3: Irradiation stability assays for PS-POM and the POM-free PS reference system.
Fig. 4: Photophysical properties of PS-POM.
Fig. 5: Spectral evolution of PS-POM upon photoreduction and acid addition.
Fig. 6: Delayed on-demand hydrogen production.

Data availability

All the data supporting the findings of this study are available within the main text of the paper and the Supplementary Information and have been deposited on Zenodo.org under https://doi.org/10.5281/zenodo.5533869.

Crystallographic data for the structure reported in this Article has been deposited at the Cambridge Crystallographic Data Centre, under deposition number CCDC no. 2045447. Copies of the data can be obtained free of charge via https://www.ccdc.cam.ac.uk/structures/.

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Acknowledgements

We gratefully acknowledge the Deutsche Forschungsgemeinschaft DFG for financial support through the TRR234 ‘CataLight’ (project no. 364549901, projects A1, A4, B2, B6 and Z2; U.S.S., S.R., B.D. and C.S.). Funding by the Federal State of Baden-Württemberg and Ulm University for a PhD fellowship (LGFG; S.K.) and a Margarete von Wrangell fellowship (M.A.) is gratefully acknowledged. We thank T. Meyer-Zedler for assistance with the time-resolved emission measurements.

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Contributions

S.A., S.K., A.K.M., S.R., B.D. and C.S. conceived the experiments and performed data analyses. S.A. and S.K. performed syntheses and characterization. S.A. and M.H. performed catalytic tests. C.L., L.Z. and B.D. performed time-resolved spectroscopy and provided data interpretation. D.N. and M.A. performed electrochemistry. W.T. and U.S.S. provided mass-spectrometric data. A.K.M. performed crystallography. All authors cowrote the manuscript.

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Correspondence to Benjamin Dietzek-Ivanšić, Sven Rau or Carsten Streb.

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Supplementary Information

Supplementary Figs. 1–27; Tables 1–3; Discussion; instrumentation, synthesis and characterization details; and spectroscopic, electrochemical, spectro-electrochemical, mass-spectrometric and single-crystal X-ray diffraction data.

Supplementary Data 1

Crystallographic data for (mPO3Et2)bpy; CCDC no. 2045447.

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Amthor, S., Knoll, S., Heiland, M. et al. A photosensitizer–polyoxometalate dyad that enables the decoupling of light and dark reactions for delayed on-demand solar hydrogen production. Nat. Chem. 14, 321–327 (2022). https://doi.org/10.1038/s41557-021-00850-8

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