Chromoselective Photocatalysis Enables Stereocomplementary Biocatalytic Pathways**

Controlling the selectivity of a chemical reaction with external stimuli is common in thermal processes, but rare in visible-light photocatalysis. Here we show that the redox potential of a carbon nitride photocatalyst (CN-OA-m) can be tuned by changing the irradiation wavelength to generate electron holes with different oxidation potentials. This tuning was the key to realizing photo-chemo-enzymatic cascades that give either the (S)- or the (R)-enantiomer of phenylethanol. In combination with an unspecific peroxygenase from Agrocybe aegerita, green light irradiation of CN-OA-m led to the enantioselective hydroxylation of ethylbenzene to (R)-1-phenylethanol (99 % ee). In contrast, blue light irradiation triggered the photocatalytic oxidation of ethylbenzene to acetophenone, which in turn was enantioselectively reduced with an alcohol dehydrogenase from Rhodococcus ruber to form (S)-1-phenylethanol (93 % ee).

Automated summary

The redox potential of a carbon nitride photocatalyst can be tuned by changing the irradiation wavelength, enabling selective generation of enantiomers of phenylethanol through photo-chemo-enzymatic cascades. Green light irradiation leads to (R)-1-phenylethanol, while blue light irradiation results in (S)-1-phenylethanol.