Polycyclic Heteroaromatics with Planar-Curved Hybrid Skeletons for High-Performance Photocatalytic Hydrogen Peroxide...

Area of Science:

• Materials Science
• Photocatalysis
• Organic Chemistry

Background:

• Polycyclic aromatic hydrocarbons (PAHs) typically exhibit planar structures.
• Molecular curvature in PAHs can unlock unique optoelectronic and self-assembly properties.
• The application of curved PAHs in photoredox catalysis remains underexplored.

Purpose of the Study:

• To synthesize novel curved PAHs incorporating a nitrogen-boron-nitrogen (N-B-N) unit.
• To investigate the impact of molecular contortion on optoelectronic properties and photocatalytic performance.
• To explore the potential of these materials for visible-light-driven hydrogen peroxide production.

Main Methods:

• Synthesis of two novel PAHs via fusion of N-arylcarbazole and dibenzophenalene precursors.
• X-ray single crystal structure analysis to confirm planar-negatively curved molecular skeletons.
• Electrochemical analysis, photophysical measurements, and theoretical calculations to evaluate properties.
• Femtosecond transient absorption spectroscopy (fs-TAS) to study excited-state dynamics.

Main Results:

• Successfully synthesized curved PAHs with a unique N-B-N unit.
• Demonstrated that increased molecular contortion leads to enhanced reversible electrochemical behavior, hydrophilicity, and charge generation/separation.
• Achieved high photocatalytic activity for hydrogen peroxide production (up to 6696 µmol h⁻¹ g⁻¹) under visible-light irradiation.
• fs-TAS revealed that more curved structures exhibit longer excited-state lifetimes and more photogenerated charges.

Conclusions:

• Molecular curvature in PAHs, particularly with N-B-N units, significantly enhances photocatalytic efficiency.
• The synthesized curved PAHs are promising candidates for sustainable hydrogen peroxide production.
• Structural contortion is a viable strategy to tune optoelectronic properties for advanced catalytic applications.