Metal-Organic Framework Breathing in the Electric Field: A Theoretical Study

In this manuscript, we study the electrically induced breathing of a metal-organic framework (MOF) within a 2D lattice model. The Helmholtz free energy of the MOF in the electric field consists of two parts: the electrostatic energy of the dielectric body in the external electric field and the elastic energy of the framework. The first contribution is calculated from the first principles of statistical mechanics with an account of MOF symmetry. By minimizing the obtained free energy and solving the resulting system of equations, we obtain the local electric field and the parameter of the unit cell (angle alpha). The paper also studies the cross-sectional area of the unit cell and the polarization as functions of the external electric field. We obtain the hysteresis in the region of the structural transition of the framework. Our results are in qualitative agreement with the literature data of the molecular dynamics simulation of MIL-53(Cr).