Piperazine-Linked Metalphthalocyanine Frameworks for Highly Efficient Visible-Light-Driven H₂O₂ Photosynthesis

Area of Science:

• Materials Science
• Photocatalysis
• Green Chemistry

Background:

• Artificial photosynthesis of H2O2 offers an energy-efficient and environmentally friendly alternative.
• Developing highly active and selective 2e- oxygen reduction reaction (ORR) photocatalysts is crucial for efficient H2O2 production.
• Current photocatalysts often suffer from unsatisfactory productivity.

Purpose of the Study:

• To synthesize novel two-dimensional piperazine-linked cobalt phthalocyanine (CoPc)-based covalent organic frameworks (COFs).
• To investigate their efficiency as photocatalysts for H2O2 production via O2 reduction under visible light.
• To establish new benchmarks for COF-based photocatalysts in artificial photosynthesis.

Main Methods:

• Synthesis of CoPc-BTM-COF and CoPc-DAB-COF via nucleophilic substitution reaction.
• Characterization using Powder X-ray diffraction, electron microscopy, and spectroscopy.
• Evaluation of photocatalytic activity for O2 to H2O2 conversion under visible light (λ > 400 nm).

Main Results:

• The synthesized COFs possess crystalline porous frameworks with fully conjugated structures and eclipsed π-stacking.
• They exhibit broad light absorption (400-1000 nm) and enhanced photo-induced charge separation/transport efficiency.
• CoPc-BTM-COF achieved a record H2O2 yield of 2096 μmol h-1 g-1 and an apparent quantum yield of 7.2% at 630 nm.

Conclusions:

• Piperazine-linked CoPc-based COFs are highly effective photocatalysts for visible-light-driven H2O2 production.
• These materials show superior performance compared to existing COF-based photocatalysts.
• The findings pave the way for developing high-performance, low-cost photocatalysts for sustainable H2O2 synthesis.