Two-dimensional metal-organic frameworks with high thermoelectric efficiency through metal ion selection

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Two-dimensional (2D) materials possess unique properties, driving significant research interest.
• Metal-organic frameworks (MOFs) are emerging as a new class of 2D materials with high electrical conductivity, a rare trait for nanoporous organic materials.
• The electronic, optical, and thermal properties of these novel 2D MOFs require fundamental investigation.

Purpose of the Study:

• To investigate the thermoelectric properties of crystalline 2D MOFs X3(HITP)2 (X = Ni, Pd, Pt).
• To explore the influence of atomic structure, specifically metal-ligand interactions and metal d orbital splitting, on thermoelectric transport.
• To identify strategies for optimizing 2D MOFs for thermoelectric applications.

Main Methods:

• Atomistic study employing ab initio transport models.
• Classical molecular dynamics simulations.
• Analysis of band structure, band alignment, and electronic density of states.

Main Results:

• The studied 2D MOFs exhibit a high Seebeck coefficient and low thermal conductivity, indicating suitability for thermoelectric applications.
• Thermoelectric properties are strongly dependent on the choice of metal ion (Ni, Pd, Pt), influenced by metal-ligand interactions and d orbital splitting.
• An unexpected deviation from the Wiedemann-Franz law was observed, with thermal and electrical currents not equally carried by holes.

Conclusions:

• Metal ion selection is a critical factor for controlling and enhancing thermoelectric properties in 2D MOFs.
• These findings provide fundamental insights for optimizing existing 2D MOFs and designing new MOF-based thermoelectric materials.
• The deviation from the Wiedemann-Franz law warrants further investigation for a deeper understanding of charge and heat transport mechanisms.