Thermoelectric performance of a copper-doped nickel benzene-1,3,5-tricarboxylate metal–organic framework

Abstract

Metal–organic frameworks (MOFs), which comprise metal cations and organic ligands connected through coordination bonds, exhibit exceptional porosity and tunable properties, making them promising for thermoelectric applications. However, most MOFs have low electrical conductivity, which limits their application in thermoelectric devices. Doping transition metal ions into MOF systems can provide adequate conductivity for thermoelectric conversion. Thus, in this study, the thermoelectric properties of Cu-doped nickel benzene-1,3,5-tricarboxylate (NiBTC) were investigated to optimize its carrier concentration and mobility. NiBTC was synthesized into a hollow structure to enhance its phonon scattering and then doped with copper to tune its electrical conductivity and Seebeck coefficient. The synthesis was confirmed through various characterization techniques, including XRD, FTIR spectroscopy, and electron microscopy. Cu doping significantly increased its electrical conductivity by ∼10% while slightly decreasing its Seebeck coefficient; however, high doping levels (15%) resulted in a CuBTC byproduct, which negatively affected its performance. The findings revealed that the substitution of Ni²⁺ with Cu²⁺ enhances its electrical performance by improving its carrier concentration and mobility, while the hollow structure reduces its thermal conductivity. The optimized Cu–NiBTC composite exhibited promising thermoelectric performance, with a maximum figure of merit of 0.571 at 473 K. This study highlights the potential of MOF-based composites for thermoelectric applications, promoting future advancements in energy-harvesting technologies.