(Invited) Metal Organic Frameworks for Thermoelectric Energy Conversion Applications

Abstract

Motivated by low cost, low toxicity, mechanical flexibility, and conformability over complex shapes, organic semiconductors are attractive as thermoelectric (TE) materials to replace the costly, brittle, and non-eco-friendly inorganic TEs for near ambient temperature applications. Metal organic frameworks (MOFs) are extended, crystalline compounds consisting of metal ions interconnected by organic ligands forming a crystalline, nanoporous structure, share many of the attractive features of all-organic polymers, including solution processability and low thermal conductivity. A potential advantage of MOFs and Guest@MOF materials for TE applications is their synthetic and structural versatility, which allows both the electronic and geometric structure to be tuned through the choice of metal, ligand, and guest molecules. These unique features could solve the long-standing challenge of finding stable, high ZT n-type organic semiconductors, as well as promote high charge mobility as a result of the long-range crystalline order inherent in MOFs. In addition, the low atomic density and long, bridge-like bonding characteristic implies that MOFs should exhibit low thermal conductivity, which is an attractive feature for thermoelectric energy conversion. In my presentation I will review the recent advances in the synthesis of MOF and Guest@MOF TEs and discuss how the Seebeck coefficient, electrical conductivity and the thermal conductivity could be tuned to further optimize their TE performance. This work was supported by the Sandia Laboratory Directed Research and Development (LDRD) Program. Sandia National Laboratories is a multi-mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.