Multinuclear Ruthenium Sites Confined in Metal-Organic Frameworks with Bio-Inspired Water Networks for Efficient...

Area of Science:

• Catalysis
• Materials Science
• Supramolecular Chemistry

Background:

• Natural enzymes utilize microenvironments for high catalytic efficiency, a feat difficult to replicate synthetically.
• Developing efficient and stable synthetic water-oxidation catalysts is crucial for energy applications.

Purpose of the Study:

• To design an enzyme-inspired metal-organic framework (MOF) integrating a mononuclear Ru-cba water-oxidation catalyst.
• To investigate the effect of nanoconfinement within the MOF on catalytic activity and mechanism.

Main Methods:

• Assembly of a mononuclear Ru-cba catalyst into a Hf-based MOF (Hf-Ru-cba).
• Characterization of catalytic pockets, hydrogen-bond networks, and multinuclear Ru-cba sites.
• Mechanistic studies using kinetics, isotope labeling, and DFT calculations.

Main Results:

• Hf-Ru-cba exhibits a turnover frequency of 20.6 s^-1, nearly 10 times higher than the discrete analogue.
• The MOF catalyst maintains high activity at ultralow concentrations (3.6 μM) and shows excellent operational stability (≥5 cycles).
• Nanoconfinement directs the reaction via the water-nucleophilic-attack (WNA) pathway, lowering the O-O bond formation barrier.

Conclusions:

• MOFs serve as programmable scaffolds for integrating molecular catalysts.
• Water-network engineering within confined spaces is a powerful strategy to enhance catalytic performance.
• The Hf-Ru-cba MOF represents a significant advancement in artificial water-oxidation catalysis.