Self-Assembly of Earth-Abundant Supraparticles with Chiral Interstices for Enantioselective Photocatalysis

Chiral nanostructures have been extensively studied for bioanalysis and optoelectronics because of their high rotatory optical activity but not for enantioselective catalysis because of the chirality mismatch of geometric scales. Here, we investigate whether the catalytic activity of supraparticles (SPs) made from ZnS NPs could provide a general pathway to reconcile the difficulties. SPs synthesized by two different pathways could enantioselectively oxidize tyrosine (Tyr). Upon illumination with 300-450 nm photons, SPs could convert Tyr into the catechol derivative dihydroxyphenylalanine (DOPA) and Tyr-Tyr dimers coupled via a C-C bond. The enantiomeric preference of substrate conversion is 23-26%, which is an order of magnitude greater than that with metalorganic compounds for the comparable catalytic process in organic solvents. Chiral catalysis substantiated by a photocatalytic oxidation of tryptophan (Trp) could predominantly lead to catechol derivatives with similar enantiomeric preference of 21-25%. This study opens the door to enantioselective catalysts for aqueous mediums taking advantage of the catalytic, photonic, and self-assembly properties of chiral NPs.