The crystal structures of UiO-67 and IRMOF-10 were optimised in the primitive unit cell shown in Figure -c using the PBEsol 21 exchange-correlation functional and the D3 correction to account for dispersion interactions. Initial geometry optimisation is performed with a plane-wave energy cutoff of 600eV, while the MD simulations are performed with a cutoff of 400eV to lower the computational overhead. A discussion of the accuracy expected from this choice of cutoff is given in the Electronic Supplementary Information (ESI) along with computational details on the setup of the DFT, lattice dynamic, and molecular dynamics calculations.