We thank M. van Gastel (Max Planck Institute for Chemical Energy Conversion) for the acquisition of electron paramagnetic resonance spectra, as well as S. Marcus and D. Kampen (Max-Planck-Institut für Kohlenforschung) for mass spectrometry analysis. We thank G. Berger for assistance with the construction of a photoreactor. We thank UCB Biopharma and the Max-Planck-Institut für Kohlenforschung for funding.

Reviewer information

Nature thanks Kuangbiao Liao and the other anonymous reviewer(s) for their contribution to the peer review of this work.