Water oxidation catalysis constitutes the bottleneck for the development of energy-conversion schemes based on sunlight. To date, state-of-the-art homogeneous water oxidation catalysis is performed efficiently with expensive, toxic and earth-scarce transition metals, but 3d metal-based catalysts are much less established. Here we show that readily available, environmentally benign iron coordination complexes catalyse homogeneous water oxidation to give O2, with high efficiency during a period of hours. Turnover numbers >350 and >1,000 were obtained using cerium ammonium nitrate at pH 1 and sodium periodate at pH 2, respectively. Spectroscopic monitoring of the catalytic reactions, in combination with kinetic studies, show that high valent oxo-iron species are responsible for the O–O forming event. A systematic study of iron complexes that contain a broad family of neutral tetradentate organic ligands identifies first-principle structural features to sustain water oxidation catalysis. Iron-based catalysts described herein open a novel strategy that could eventually enable sustainable artificial photosynthetic schemes.
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We thank R. Hage, X. Ribas and P. Lahuerta for reading this work and for comments. We thank the European Research Foundation for project FP7-PEOPLE-2010-ERG-268445 (J.Ll.), El Ministerio de Ciencia e Innovación for project CTQ2009-08464 (M.C.), for a Ramon y Cajal contract (J.Ll.) and for a PhD grant (I.G-B.), Generalitat de Catalunya for an ICREA Academia Award and the European Research Council for Project ERC-2009-StG-239910 (M.C.). RahuCat is acknowledged for giving the tritosylTACN.
The authors declare no competing financial interests.
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Fillol, J., Codolà, Z., Garcia-Bosch, I. et al. Efficient water oxidation catalysts based on readily available iron coordination complexes. Nature Chem 3, 807–813 (2011). https://doi.org/10.1038/nchem.1140
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