Reticular Synthesis of 3D Metal Cluster‐based COFs with Record High‐Connectivity for Efficient Photocatalytic H2O2 Synthesis

The assembly of metal clusters with organic building units by covalent bonds to form crystalline metal cluster‐based covalent‐organic frameworks (MCCOFs) material is a novel strategy in the field of reticular synthesis. However, only 2, 3, and 6 connectivity (valency) of metal cluster‐based MCCOFs have been achieved in reported structures. Developing a higher connectivity remains a great challenge in the MCCOFs structural design due to the difficulties for introducing multiple connecting nodes to metal cluster. In this work, two crystalline 3D [8+2]‐connected MCCOFs were synthesized by condensing an 8‐connectivity aluminum cluster‐based building block (termed Al8‐8c) with linear dialdehyde linkers. Furthermore, these AlCCOFs showed efficient photocatalytic O2‐to‐H2O2 conversion due to the suitable energy band structure, efficient photoelectron conversion capability and highly dispersed active sites. Especially, the AlCCOF‐1 showed high H2O2 photosynthetic efficiency of 16794.69 μmol g‐1 h‐1 with an apparent quantum yield (AQY) of 7.1% at 420 nm. The in situ EPR, in situ FTIR and DFT calculations were then performed to study the structure‐function relationships on the two AlCCOFs for H2O2 photosynthesis.