A Recyclable Supramolecular Photocatalyst for the Chemoselective [2+2] Photocycloaddition of Chalcones in Water

Herein, we disclose a recyclable supramolecular photocatalytic system that enables efficient intermolecular homo- and cross-[2 + 2] photocycloadditions of chalcones in an aqueous medium. This was accomplished through the synergistic covalent dispersion of thioxanthones (TXOs) and substrate aggregation on the protein surface. Our experimental findings indicate that this supramolecular approach effectively suppresses the detrimental aggregation-caused quenching phenomenon of thioxanthone and the competing E/Z isomerization of chalcones. This catalyst was recycled five times, obtaining an accumulative turnover number (TON) of 4370. This study provides a novel strategy for harnessing supramolecular interactions to promote selective photochemical reactions in a sustainable manner and provides valuable insights for designing supramolecular photocatalysis with improved photophysical properties.