Benchmark Investigation of SCC-DFTB Against Standard Dft to Model Electronic and Phononc Properties in Two-Dimensional MOFs for Thermoelectric Applications

Metal–organic frameworks (MOFs) are two or three-dimensional ultrahigh porosity materials that consist of metal nodes connected by organic linkers. MOFs have the potential to be used as thermoelectric materials. Thermoelectric materials use temperature differences to generate electrical energy. The main motivation for this project is to further our knowledge of thermoelectric properties in MOFs and find which available self-consistent-charge density functional tight-binding (SCC-DFTB) method can best predict (at least trends in) the electronic, phononic and therefore thermoelectric properties of MOFs at a lower computational cost than standard density functional theory (DFT). To this end, we compared SCC-DFTB/3ob and SCC-DFTB/mio, GFN1-xTB and GFN2-xTB against PBE and hybrid DFT (HSE06) for Zn3C6O6, Zn-NH-MOF, Ni3(HITP)2 and Cd3C6O6 2D MOFs for the monolayer and stacked AA, serrated and AB structures. In this talk, we present these findings as well as additional modeling insights gleaned from this work. The latter includes teasing apart the relative importance of correctly predicting band shape compared to band gap in estimating thermoelectric performance. Among the MOFs modeled, Zn3C6O6, Zn-NH-MOF and Cd3C6O6 are predicted to have a higher power factor than Ni3(HITP)2 (one of the highest performing synthesized thermoelectric MOFs), and that thermal transport is substantially lower for Zn-NH-MOF, leading to the highest ZT among the group.