Electrically Conductive π-Intercalated Graphitic Metal-Organic Framework Containing Alternate π-Donor/Acceptor Stacks

Area of Science:

• Materials Science
• Nanotechnology
• Electrochemistry

Background:

• Two-dimensional graphitic metal-organic frameworks (GMOFs) exhibit good in-plane conductivity but suffer from poor out-of-plane charge transport.
• This conductivity anisotropy limits the overall bulk electrical performance of GMOFs.

Purpose of the Study:

• To engineer higher bulk electrical conductivity in 2D GMOFs.
• To overcome the limitations of inefficient out-of-plane charge transport in stacked 2D GMOF layers.

Main Methods:

• A bottom-up synthesis approach was employed to construct the first π-intercalated GMOF (iGMOF1).
• The iGMOF1 features alternating stacks of π-donor/acceptor (π-D/A) components: Cu^II-coordinated hexaaminotriphenylene (HATP) ligands and hexacyano-triphenylene (HCTP) molecules.
• This design facilitates both in-plane conduction through the Cu₃(HATP)₂ scaffold and out-of-plane conduction via the π-D/A stacks.

Main Results:

• The synthesized iGMOF1 demonstrated an order of magnitude higher bulk electrical conductivity compared to the parent Cu₃(HATP)₂ material (25 S/m vs. 2 S/m).
• iGMOF1 exhibited a significantly smaller activation energy (36 meV) than Cu₃(HATP)₂ (65 meV).
• The enhanced conductivity is attributed to simultaneous in-plane (through-bond) and out-of-plane (through π-D/A stacks) charge transport.

Conclusions:

• The successful construction of iGMOF1 validates the π-intercalation strategy for enhancing electrical conductivity in 2D GMOFs.
• Simultaneous in-plane and out-of-plane charge transport pathways are crucial for achieving high bulk conductivity.
• This work opens avenues for designing novel iGMOFs with superior electrical properties for advanced applications.