The Molecular Dynamics simulations for the calculation of diffusion coefficients were performed aiming for a constant (and finite) volumetric loading of adsorbed molecules: 1/R 3 c . Given that R c = 12.8 Å and the simulation box has at least (2R c ) 3 volume, this leads to a volumetric loading of at most 792 mol/m 3 , which translates to a gravimetric loading of the order of 1 mol/kg. This led to a different number of molecules per simulation box for each material, given that each structure had a different unit cell size. The NVT ensemble was used with a Nosé-Hoover thermostat, and the integration time step was 10 fs. We performed 1000 GCMC cycles for initialization, 9000 MD steps (90 ps) for equilibration and 5,000,000 MD steps (50 ns) for production. The mean squared displacement (MSD) was calculated based on the trajectories of the molecules by applying the n-order algorithm. 72