Precise tuning of interlayer electronic coupling in layered conductive metal-organic frameworks

Area of Science:

• Materials Science
• Nanotechnology
• Solid-State Physics

Background:

• Two-dimensional conjugated metal-organic frameworks (2D c-MOFs) are promising for optoelectronics and spintronics due to their layer-dependent electronic properties.
• Current research focuses on intralayer charge transport, with limited control over electronic coupling between layers.
• Precise control of interlayer charge transport is crucial for optimizing the performance of 2D c-MOFs.

Purpose of the Study:

• To develop a strategy for precisely tuning interlayer charge transport in 2D c-MOFs.
• To investigate the effect of controlled layer spacing on the electronic and thermoelectric properties of 2D c-MOFs.
• To achieve enhanced thermoelectric performance in semiconducting metal-organic frameworks.

Main Methods:

• Designed hexaiminotriindole (HATI) ligands functionalized with varying alkyl chain lengths (HATI_CX, X=1,3,4).
• Synthesized semiconducting Ni3(HATI_CX)2 materials with precisely controlled layer spacings (3.40–3.70 Å).
• Characterized the electronic and thermoelectric properties, including band gap, carrier mobility, and Seebeck coefficient.

Main Results:

• Successfully tuned the layer spacing of Ni3(HATI_CX)2 MOFs by modifying alkyl chain lengths.
• Observed a widened band gap and suppressed carrier mobilities with increased layer spacing.
• Achieved a record-high thermoelectric power factor of 68 ± 3 nW m⁻¹ K⁻² in Ni3(HATI_C3)2.

Conclusions:

• Side-chain engineering of ligands provides a precise method to control interlayer spacing and charge transport in 2D c-MOFs.
• Controlled interlayer coupling significantly enhances thermoelectric properties, particularly the Seebeck coefficient.
• The developed strategy offers a pathway to optimize 2D c-MOFs for advanced thermoelectric applications.