Biomimetic Design of Mn-Based Molecular Water Oxidation Catalysts: Nuclearity, Ligand Engineering, and Auxiliary Strategies

The water oxidation reaction represents an essential yet kinetically demanding bottleneck in artificial photosynthesis, requiring a challenging multi-electron/proton transfer process. Remarkably, the native oxygen-evolving complex in photosystem II carries out this reaction with high efficiency in mild conditions. The functionality of the Mn4CaO5 cluster that constitutes the active site offers an ideal model for designing active artificial molecular catalysts. In this contribution, we critically summarize the progress of biomimetic Mn-based molecular water oxidation catalysts in terms of three crucial and interrelated aspects: nuclearity-controlled structure design, fine ligand tuning, and novel assistant strategies. Through combining the basic biomimicking methodologies with the rational structural and functional tuning, our work attempts to offer a clear guiding principle for the future design of Mn-based systems toward highly efficient artificial photosynthesis devices and sustainable energy storage.