Noble Metal-Free Photosensitive Terpyridine Coordination Assemblies for Efficient Single-Molecule H₂O₂ Photocatalysis

Conventional molecular photocatalysts characterized by long-lived excited states, such as Ru and Ir complexes are widely recognized and used in photocatalysis. However, developing new heavy atom-free photosensitive coordination complexes by manipulating their molecular structures to achieve highly efficient photocatalytic reactions remains challenging. In this study, a series of novel terpyridine complexes, S1-S4, with a rigid donor-acceptor configuration was designed and synthesized via precise heteroleptic, coordination-driven self-assembly. Experimental data, combined with theoretical calculations, confirmed that long-lived charge-transfer excited states were generated, enabling excellent photosensitivity. Furthermore, high-efficiency photocatalytic total synthesis of H₂O₂ was achieved in pure water under an air atmosphere via a synergetic process of energy transfer and electron transfer to form ¹O₂ and •O₂ ^-, respectively, in these complexes, differing significantly from previous reports on polymer catalysts. Notably, complex S1 exhibited an outstanding photocatalytic H₂O₂ production rate of 10 mmol g^-1 h^-1, outperforming most organic photocatalytic systems. In addition, S1 achieved a photocatalytic rate of up to 40 mmol g^-1 h^-1 and a solar-to-chemical conversion of 1.23% with the sacrificial agent. This study not only paves the way for the development of novel noble metal-free photocatalysts but also introduces a novel photocatalytic paradigm for the green and high-performance synthesis of H₂O₂.