Structural optimisation of the BPDC linker in IRMOF-10 5 using density functional theory (DFT) found an equilibrium dihedral angle of ↵ = ±30 31 , confirming the preference for a nonplanar geometry in this material. Furthermore this is in agreement with previous calculations of the isolated carboxylic acid. However, diffraction data does not reveal if the split occupancy appears as a result of static disorder, i.e. a disordered distribution of linker orientations throughout the crystal, or dynamic disorder, i.e. the dynamical switching of individual linkers between the two equilibrium positions. The dynamic behavior of UiO-67 has previously been simulated, showing large thermal displacements of the ligand atoms, but the details of the ring torsion and mechanism of disorder was not addressed. In this study, we use a combination of ab initio molecular dynamics (MD) simulations and DFT-based phonon calculations to investigate the dynamic behaviour of the BPDC linkers in UiO-67. The MD simulations show that the linkers rotate between the two equilibrium positions at room temperature. The vibrational calculations confirm that the average structure reported experimentally is a saddle point on the potential energy surface. Imaginary harmonic phonon modes are found that correspond to phenyl ring rotations in an anharmonic double well potential. The time constant for the oscillation is found to be ⇠ 2 ps with an energy barrier of ⇠ 40 meV. Similar behaviour is also found for IRMOF-10.