Ligand-Engineered Metal-Organic Cages Boost Charge Separation for Efficient Photocatalytic Synthesis of Hydrogen Peroxide in Pure Water.

Photocatalytic synthesis of hydrogen peroxide (H2O2) offers a sustainable alternative to the traditional anthraquinone process, yet its efficiency is often hampered by the rapid recombination of photogenerated charges and the instability of reactive intermediates. Herein, we report a tetrahedral Zn(II) ion coordinated metal-organic cage (MOC) C3 constructed from a C3-symmetric terpyridine ligand incorporating pyridinium units. In pure water under an O2 atmosphere and without sacrificial agents, C3 exhibits an H2O2 generation rate of 678.15 µmol L-1 h-1. Moreover, the confined cavity of the MOC is proposed to help stabilize crucial intermediates (*OH from water oxidation and *OOH from oxygen reduction), thereby further promoting the catalytic performance. This work illustrates a ligand-engineering strategy for photocatalyst design by employing functionalized ligands to construct MOC that primarily improve charge-separation efficiency and create directional electron-transfer channels within the cage framework, while the confined microenvironment secondarily stabilizes key reactive intermediates, thus offering a route toward advanced photocatalytic H2O2 generation.