Low-Dimensional Porous Carbon Networks Using Single-/Triple-Coupling Polycyclic Hydrocarbon Precursors

Area of Science:

• Materials Science
• Organic Chemistry
• Surface Science

Background:

• Polycyclic hydrocarbons (PHs) exhibit graphene-like structures with tunable electronic properties.
• Quantum confinement in PHs creates an energy gap, crucial for electronic applications.
• Understanding covalent bonding's role in PH electronic properties is essential for advanced materials.

Purpose of the Study:

• To investigate surface-mediated synthesis of hexa-peri-hexabenzocoronene (HBC) and its oligomers.
• To explore the impact of single- and triple-covalent coupling on the electronic properties of HBC oligomers.
• To demonstrate the potential for creating conjugated polymers and porous carbon networks from HBC oligomers.

Main Methods:

• Surface-mediated synthesis of HBC and its oligomers.
• High-resolution low-temperature scanning tunneling microscopy (STM) for atomic structure determination.
• Noncontact atomic force microscopy (AFM) for structural analysis.
• Scanning tunneling spectroscopy (STS) to measure energy gaps (HOMO-LUMO).
• Density functional theory (DFT) calculations to understand electronic delocalization.

Main Results:

• Successful synthesis of HBC oligomers via single- and triple-coupling pathways.
• STS measurements revealed that increasing oligomer length narrows the HOMO-LUMO energy gap.
• Triple-coupled HBC oligomers exhibited smaller energy gaps compared to single-coupled ones.
• DFT calculations supported enhanced π-electron delocalization in triple-coupled systems.
• HBC oligomers were shown to form conjugated polymers and porous carbon networks.

Conclusions:

• Covalent bonding strategies significantly influence the electronic properties of HBC oligomers.
• Triple coupling offers a pathway to achieve smaller energy gaps and enhanced electron delocalization.
• HBC oligomers are versatile building blocks for advanced carbon-based materials and polymers.