Non-noble Metal Single-Molecule Photocatalysts for the Overall Photosynthesis of Hydrogen Peroxide

Abstract

Despite the great progress in molecule photocatalytic solar energy conversion, it is particularly challenging to realize a photocatalytic overall reaction in a non-noble metal complex, which represents a new paradigm for photosynthesis. In this study, a class of novel non-noble metal complexes with head-to-tail geometry were designed and readily synthesized via the coordination of triphenylamine-modified 2,2': 6',2″-terpyridine ligands with Zn²⁺. As expected, these complexes exhibited the desired through-space charge-transfer transition, generating both long-lived excited states (on the order of microseconds) and separate redox centers under visible-light irradiation. These complexes have particularly low exciton binding energies, which make them excellent heterogeneous single molecular photocatalysts for the overall photosynthetic production of H₂O₂. Remarkably, a high H₂O₂ evolution rate (8862 μmol g^-1 h^-1) was achieved in pure H₂O under an air atmosphere via precise molecular tailoring, revealing the unparalleled advantages of molecular photocatalysts in improving the catalytic rate of H₂O₂ production. This is the first time that single-molecule photocatalysts have been used to efficiently complete the photosynthesis of H₂O₂. This study presents a new paradigm for photocatalytic energy conversion and provides unique insights into the design of molecular photocatalysts.