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Issue 6, 2018
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Solvent exchange in preformed photocatalyst-donor precursor complexes determines efficiency

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Abstract

In homogeneous photocatalytic reduction of CO2, it is widely assumed that the primary electron transfer from the sacrificial donor to the catalyst is diffusion controlled, thus little attention has been paid to optimizing this step. We present spectroscopic evidence that the precursor complex is preformed, driven by preferential solvation, and two-dimensional infrared spectroscopy reveals triethanolamine (donor)/tetrahydrofuran (solvent) exchange in the photocatalyst's solvation shell, reaching greatest magnitude at the known optimal concentration (∼20% v/v TEOA in THF) for catalytically reducing CO2 to CO. Transient infrared absorption shows the appearance of the singly reduced catalyst on an ultrafast (<70 ps) time scale, consistent with non-diffusion controlled electron transfer within the preformed precursor complex. Identification of preferential catalyst–cosolvent interactions suggests a revised paradigm for the primary electron transfer, while illuminating the pivotal importance of solvent exchange in determining the overall efficiency of the photocycle.

Graphical abstract: Solvent exchange in preformed photocatalyst-donor precursor complexes determines efficiency

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Publication details

The article was received on 18 Oct 2017, accepted on 20 Dec 2017 and first published on 21 Dec 2017


Article type: Edge Article
DOI: 10.1039/C7SC04533F
Citation: Chem. Sci., 2018,9, 1527-1533
  • Open access: Creative Commons BY license
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    Solvent exchange in preformed photocatalyst-donor precursor complexes determines efficiency

    Laura M. Kiefer and K. J. Kubarych, Chem. Sci., 2018, 9, 1527
    DOI: 10.1039/C7SC04533F

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