Ab-initio Study of the Electron Mobility in a Functionalized UiO-66 Metal Organic Framework

Abstract

This study leverages density functional theory accompanied with Boltzmann transport equation approaches to investigate the electronic mobility as a function of inorganic substitution and functionalization in a thermally stable UiO-66 metal-organic framework (MOF). The MOFs investigated are based on Zr-UiO-66 MOF with three functionalization groups of benzene dicarboxylate (BDC), BDC functionalized with an amino group ($\hbox {BDC} + \hbox {NH}_2$) and a nitro group ($\hbox {BDC} + \hbox {NO}_2$). The design space of this study is bound by UiO-66(M)-R, [$\hbox {M}=\hbox {Zr}$, Ti, Hf; $\hbox {R}=\hbox {BDC}$, $\hbox {BDC}+\hbox {NO}_2$, $\hbox {BDC}+\hbox {NH}_2$]. The elastic modulus was not found to vary significantly over the structural modification of the design space for either functionalization or inorganic substitution. However, the electron–phonon scattering potential was found to be controllable by up to 30% through controlled inorganic substitution in the metal clusters of the MOF structure. The highest electron mobility was predicted for a UiO-66($\hbox {Hf}_5\hbox {Zr}_1$) achieving a value of approximately $1.4\times 10^{-3}\,\hbox {cm}^2$/V s. It was determined that functionalization provides a controlled method of modulating the charge density, while inorganic substitution provides a controlled method of modulating the electronic mobility. Within the proposed design space the electrical conductivity was able to be increased by approximately three times the base conductivity through a combination of inorganic substitution and functionalization.