Introducing Photochemical Action Plots as a Tool for Unlocking On–Off Switchable Behavior in a Polymeric Eosin Y Photocatalyst

Abstract Photochemical action plots are a powerful tool for investigating the wavelength‐dependent efficiency of photochemical processes. Herein, we apply the photochemical action plot methodology developed by the Barner–Kowollik team to a photocatalytic reaction, resulting in the first examples of photocatalytic action plots, paving the way for future in‐depth explorations of the wavelength dependence of similar reactions. Specifically, we investigate the wavelength dependence of the catalytic oxidation capabilities of an Eosin Y functionalized polymer photocatalyst ( P1 ) as well as a small molecule representative of the polymer bound Eosin Y moieties ( EY ) for the oxidation of triphenylphosphine. Introduction of zinc(II) ions into the system proved to drastically influence the optical absorption properties of both catalysts, accompanied by a pronounced influence on their wavelength‐dependent reactivity profiles which is not predictable based on the absorption spectra. For P1 , these changes can be reversed by metal‐mediated single‐chain nanoparticle (SCNP) formation upon base addition, giving access to a stimuli‐responsive polymeric photocatalyst. Detailed analysis of the photocatalytic action plots enabled the identification of a suitable wavelength for the realization of an on‐off switchable polymeric photocatalytic system.