Visible Light-Driven Hydrogen Evolution By Covalent Photosensitizer-Polyoxometalate-Catalyst Triads

The design of covalent photosensitizer-bridge-catalyst triads holds great promise for single-molecule species for light-driven energy conversion and storage. Here, we report the design of an asymmetrically organo-functionalized Anderson polyoxometalate, equipped with two 2,2’-bipyridine binding sites. At the first site, we installed an Ir complex photosensitizer, while at the second site, a {PtCl2} hydrogen evolution reaction (HER) catalyst was placed. Light-driven HER studies demonstrated the principal reactivity of the molecular species (reaching TONs of ca. 200 after 24 h irradiation). Combined photophysical and theoretical studies shed light on the electronic structure and charge-separation and transfer properties of the triad. This first-of-its-kind example of a polyoxometalate-based photoactive triad opens new pathways for developing molecular light-harvesting and hydrogen producing systems.