Band Engineering via Charge Modulation Drives High Thermoelectric Performance in Conductive MOFs

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Metal-organic frameworks (MOFs) show potential for thermoelectric applications due to low thermal conductivity.
• Conductive MOFs often have metallic properties, limiting their thermoelectric efficiency via low Seebeck coefficients and high electronic thermal conductivity.

Purpose of the Study:

• To develop a band-engineering strategy for MOFs to enhance thermoelectric properties.
• To investigate the effect of controlled charge modulation on the electronic structure of MOFs.

Main Methods:

• Utilized density functional theory (DFT), electron-phonon coupling, and Boltzmann transport calculations.
• Employed copper benzenehexathiol (CuBHT) as a model system.
• Investigated the impact of altering metal center oxidation states (Cu+/Cu2+) and applying compressive strain.

Main Results:

• Achieved a metal-to-semiconductor transition by adjusting Cu+/Cu2+ states, creating a band gap.
• Observed a significant increase in the Seebeck coefficient and a reduction in electronic thermal conductivity.
• Demonstrated a zT increase of nearly two orders of magnitude, reaching a maximum of 0.79 at 550 K with 5% compressive strain.

Conclusions:

• Controlled charge modulation is an effective strategy for optimizing MOF band structures for thermoelectrics.
• Engineered MOFs can achieve high thermoelectric performance, rivaling established materials.
• This approach offers a pathway to high-performance MOF-based thermoelectric devices.