A Two-Dimensional Poly(azatriangulene) Covalent Organic Framework with Semiconducting and Paramagnetic States

Area of Science:

• Materials Science
• Organic Chemistry
• Nanotechnology

Background:

• Covalent organic frameworks (COFs) are crystalline porous polymers with tunable properties.
• Triangulene-based materials offer unique electronic and optical characteristics.

Purpose of the Study:

• To synthesize and characterize a novel (aza)triangulene-based covalent organic framework (TANG-COF).
• To investigate the electronic and magnetic properties of TANG-COF for potential applications.

Main Methods:

• One-pot, two-step synthesis involving Pd-catalyzed hydrogenation and polycondensation.
• Characterization of crystallinity, porosity, and electronic structure using X-ray diffraction and spectroscopy.
• Density Functional Theory (DFT) calculations to understand electronic band dispersion.

Main Results:

• Successfully synthesized black crystalline TANG-COF with high crystallinity and permanent porosity.
• Observed broad visible and NIR absorptions (Eg ≈ 1.2 eV) due to the electron-rich TANG building block.
• Achieved high electrical conductivity (up to 10⁻² S/cm) via p-doping, attributed to high HOMO energy (-4.8 eV).
• Demonstrated room-temperature paramagnetic behavior with a spin concentration of ~10%.

Conclusions:

• TANG-COF is a promising material for electronic and spintronic applications.
• The π-electron rich TANG unit and layered structure facilitate high conductivity and magnetic properties.
• Further research into doping and device integration is warranted.