Controlling Activity by Self-Assembly – Tuning Perylene Bisimide Photocatalysts for the Hydrogen Evolution Reaction

Amino acid functionalised perylene bisimides (PBIs) form self-assembled structures in solution, the nature of which depends on the local environment. Using a high throughput photocatalysis set-up, we have studied five PBIs for the hydrogen evolution reaction (HER) under a range of conditions (pH and hole scavenger concentration) across 350 experiments to explore the relationship between supramolecular structure and photocatalytic activity. Using small angle X-ray scattering (SAXS), we show that photocatalytic activity is determined by the nature of the self-assembled aggregate that is formed with a correlation between the presence of charged flexible cylindrical aggregates and high levels of H2. Our work highlights the complexity of designing supramolecular photocatalysts, and also the power of tuning activity by the type of aggregate that is formed.