Thermoelectric properties of semiconducting metal-organic framework thin films and composites

Abstract

In order to study the potential application and efficiency of semiconducting metal organic frameworks (MOFs) as materials for thermoelectric generators (TEG), 2- dimensional and 3- dimensional frameworks have been selected as initial targets. The 2-D framework employed in this investigation possess a honeycomb-like structure, containing Cu ions as nodes and coordinated to hexahydroxytriphenylene (HHTP) organic ligands. In addition, principle experimental studies on the incorporation of molecular iodine on thin films of this framework, Cu3(HHTP)2, via incipient wetness impregnation is demonstrated as an effective route to enhance its thermoelectric performance. Furthermore, the solvothermal synthesis and thermoelectric characterisation of a semiconducting 3-D MOF comprised of divalent FeII/III ions coordinated to tetrahydroxybenzoquinone (THBQ) organic moieties and core-shell like structures constituting Fe-THBQ coated Bi2Te3 nanowires are reported for the first time, expanding the scope of MOF heterostructures in energy conversion technologies. Thermoelectric measurements were performed on MOF pellets and thin films. The incorporation of MOFs as thin films provides a route for the design of new devices, although this is still an issue that is derived from the micro-sized crystals and their poor solubility in any solvent. Especially for those MOFs that exhibit electrical conductivity, the deposition of MOFs onto a given substrate is becoming important in order to assess them in practical applications such as chemical sensors, catalytic coatings and other electronic nanodevices. The fabrication of MOF thin films was conducted via electrochemical and dip coating techniques. The study of different structures of MOFs and their performance as TEGs is expected to expand and offer alternatives to non-toxic, scalable and high-efficiency novel TE materials

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ORCID for Iris Nandhakumar: orcid.org/0000-0002-9668-9126

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