In our previous study on kinetic trapping of xenon in MFU-4, classical molecular dynamics simulations using a reparametrized universal force field and assuming an NVT ensemble were performed for MFU-4 loaded with 15 Xe atoms in the central pore. Even though a temperature range of 200 K to 450 K was investigated, hopping from void to void for Xe in MFU-4 was found only scarcely even for sampling times of 30 ns. Diffusion of Xe through the network structure was thus computationally shown to be very slow in line with the concept of kinetic trapping. Nudged-elastic band (NEB) computations enabled to predict an activation barrier of 66 kJ•mol for Xe diffusion at GGA level of accuracy using the PBEsol functional and including dispersion corrections as suggested by Tkatchenko and Scheffler. Analogous computations for moving a Kr atom from the large to the small pore of MFU-4 resulted in an activation barrier of 46 kJ•mol -1 (Table ).