Self-assembled molecular rafts at liquid|liquid interfaces for four-electron oxygen reduction

Area of Science:

• Catalysis
• Supramolecular Chemistry
• Electrochemistry

Background:

• Water-soluble porphyrins self-assemble at interfaces.
• Molecular rafts can act as catalysts.
• Interfacial catalysis is crucial for energy conversion.

Purpose of the Study:

• To develop a novel self-assembled catalyst for oxygen reduction.
• To investigate the catalytic activity and selectivity of cobalt porphyrin rafts.
• To understand the mechanism of interfacial oxygen reduction.

Main Methods:

• Self-assembly of cobalt tetramethylpyridinium porphyrin (CoTMPyP(4+)) and cobalt tetrasulphonatophenyl porphyrin (CoTPPS(4-)).
• Interfacial four-electron reduction of oxygen using lipophilic electron donors (e.g., tetrathiafulvalene).
• Characterization using UV-visible spectroscopy, Surface Second Harmonic Generation, and Scanning Electron Microscopy.
• Density functional theory (DFT) calculations.

Main Results:

• Formation of molecular rafts at the organic solvent interface.
• The self-assembled catalyst exhibits high activity and selectivity for the four-electron oxygen reduction pathway.
• Catalytic performance comparable to cofacial cobalt porphyrins.
• DFT calculations confirm complex formation and oxygen binding capability.

Conclusions:

• Self-assembled porphyrin rafts provide an efficient catalytic system for interfacial oxygen reduction.
• This system mimics enzymatic activity and offers a promising alternative to existing catalysts.
• The study elucidates the structural and electronic properties enabling this catalytic function.