Guest-Enhanced Charge Separation in Porphyrin-Based Double-Cavity Metallacages for Visible-Light-Driven H₂O₂...

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Photocatalysis

Background:

• Hydrogen peroxide (H2O2) is a key industrial oxidant, but its production via the anthraquinone process is energy-intensive.
• Photocatalytic H2O2 synthesis under visible light presents a sustainable alternative, yet faces challenges in charge separation and mass transport in materials.

Purpose of the Study:

• To design and construct novel porphyrin-based double-cavity metallacages for enhanced photocatalytic H2O2 production.
• To investigate the role of encapsulated guests in improving charge separation and carrier lifetimes for improved H2O2 generation.

Main Methods:

• Modular synthesis of porphyrin-based double-cavity metallacages using orthogonal coordination chemistry (Pt(II)/carboxylate/pyridine and Zn-porphyrin/pyridine).
• Incorporation of electron-rich aromatic guests (triphenylene or benzotrithiophene) within the metallacage cavities.
• Evaluation of photocatalytic H2O2 generation rates under visible light in the presence of benzyl alcohol.

Main Results:

• The synthesized metallacages possess an intrinsic donor-acceptor architecture facilitating photoinduced electron transfer and charge separation.
• Encapsulation of guests significantly stabilized the charge-separated state and prolonged carrier lifetimes.
• Achieved a high H2O2 generation rate of 4037 µmol·g⁻¹·h⁻¹, among the highest for visible-light supramolecular photocatalysts.

Conclusions:

• Discrete metallacages and their host-guest complexes represent a promising platform for supramolecular photocatalysis.
• This approach offers a rational strategy for H2O2 photosynthesis, advancing sustainable chemical production.
• The developed metallacages pave the way for future applications in photocatalysis.