Substrates In Situ Formed Dynamic Secondary Coordination Environment Regulates Reaction Pathways and Product Selectivity.

In enzymes, a protein-scaffolded secondary coordination sphere plays a crucial role in reaction activity and selectivity. As such, pre-installed active sites on catalysts are employed to mimic the natural secondary coordination environment for chemical transformations. Herein, we identify that varying the concentration of substrate (KNO3), rather than pre-installed motifs surrounding active sites of photocatalyst CdS quantum dots, forms a secondary coordination environment in situ. Spectroscopic and kinetic studies reveal that the in situ secondary coordination environment controls the reaction pathways and product selectivity of benzyl alcohol oxidation, synthetically valuable yet competitive pathways. Upon irradiation of photocatalyst CdS quantum dots, deoxybenzoin is obtained with 88.2% yield and 90.4 mmol·gcat -1·h-1 formation rate at 50 mM KNO3, while benzaldehyde is obtained with 87.2% yield and a formation rate of 357.4 mmol·gcat -1·h-1 at 200 mM KNO3. Such a profound difference in product selectivity has not yet been realized. Different from pre-installed active sites, simply varying substrate concentration in situ enables efficient regulation of reaction pathways and product selectivity of chemical transformation.