Solvent-Directed Assembly of π-Stacked 3D Metal-Organic Frameworks with Tunable Conductivity Enhanced by C₆₀...

Area of Science:

• Materials Science
• Chemistry
• Solid State Physics

Background:

• Metal-organic frameworks (MOFs) show promise as conductive materials due to their tunable structures and host-guest chemistry.
• Systematic studies on the interplay between conductivity, porosity, and structural tunability in conductive MOFs are lacking.

Purpose of the Study:

• To synthesize and systematically investigate a series of 3D copper MOFs with varying conductivity and porosity.
• To explore the effect of guest molecule encapsulation on the electrical properties of MOFs.

Main Methods:

• Synthesis of a series of 3D copper MOFs (NU-4000 to NU-4003) using a triphenylene-based hexatopic carboxylate linker.
• Modulation of solvent ratios to control MOF topology and π-π stacking.
• Encapsulation of C60 fullerene within MOF channels to enhance conductivity.

Main Results:

• Achieved electrical conductivities ranging from insulators (<10^-6 S/cm) to semiconductors (10^-8 to 10^2 S/cm) by tuning solvent ratios.
• NU-4003 MOF with continuous π-π stacking exhibited conductivity of 1.7 × 10^-6 S/cm.
• Encapsulation of C60 in NU-4003 resulted in an eight-order magnitude conductivity enhancement to 140 S/cm, with high pore occupancy.

Conclusions:

• The combination of π-π stacking and host-guest chemistry in MOFs significantly enhances electrical conductivity.
• NU-4003-C60 represents one of the most conductive 3D MOFs reported, demonstrating potential for electronic and energy applications.
• This work provides a blueprint for designing conductive MOFs with retained porosity through integrated charge transport pathways.