Tuning the Electric Field Response of MOFs by Rotatable Dipolar Linkers

Abstract

Recently the possibility of using electric fields as a further stimulus to trigger structural changes in metal–organic frameworks (MOFs) has been investigated. In general, rotatable groups or other types of mechanical motion can be driven by electric fields. In this study we demonstrate how the electric response of MOFs can be tuned by adding rotatable dipolar linkers, generating a material that exhibits paraelectric behavior in two dimensions and dielectric behavior in one dimension. The suitability of four different methods to compute the relative permittivity κ by means of molecular dynamics simulations was validated. The dependency of the permittivity on temperature T and dipole strength μ was determined. It was found that the herein investigated systems exhibit a high degree of tunability and substantially larger dielectric constants as expected for MOFs in general. The temperature dependency of κ obeys the Curie–Weiss law. In addition, the influence of dipolar linkers on the electric field induced breathing behavior was investigated. With increasing dipole moment, lower field strengths are required to trigger the contraction. These investigations set the stage for an application of such systems as dielectric sensors, order–disorder ferroelectrics, or any scenario where movable dipolar fragments respond to external electric fields.

Molecular Dynamics Simulations of the “Breathing” Phase Transformation of MOF Nanocrystallites

“…[8][9][10][11] In general, they can be triggered not only by guest adsorption but also by pressure, temperature, and other stimuli like electric fields. [12,13] Albeit a number of network topologies allow for volumechanging transformations, [14] the so called "wine rack" deformation of pcu like topologies is most often observed and studied. In particular the MIL-53 series was most intensively investigated both experimentally and theoretically.…”

“…In order to understand, predict, and exploit this key feature of MOFs, a variety of experimental and theoretical investigations of such phenomena has been performed . In general, they can be triggered not only by guest adsorption but also by pressure, temperature, and other stimuli like electric fields . Albeit a number of network topologies allow for volume‐changing transformations, the so called “wine rack” deformation of pcu like topologies is most often observed and studied.…”

Reticular Chemistry in All Dimensions

“…It is intriguing to imagine the possibility that variations in the applied current would lead to structural switching for highly selective separations, and eventually to giving rise to electrical swing adsorption. An elegant approach to addressing specific molecular units is given by Schmid et al 8 They introduce rotatable groups or other types of mechanical motion within the organic linkers. These motions are believed to be driven by electric fields.…”

Molecular Dynamics Simulations of the “Breathing” Phase Transformation of MOF Nanocrystallites

“…[8][9][10][11] In general, they can be triggered not only by guest adsorption but also by pressure, temperature, and other stimuli like electric fields. [12,13] Albeit a number of network topologies allow for volumechanging transformations, [14] the so called "wine rack" deformation of pcu like topologies is most often observed and studied. In particular the MIL-53 series was most intensively investigated both experimentally and theoretically.…”