To obtain Free Energies of Adsorption/Hydration, Free Energy Perturbation in combination with Bennet's acceptance ratio method (BAR) was employed. We make use of the concept of thermodynamic cycles to connect the Free Energy of Adsorption and the Free Energy of Hydration since both quantities are referenced to the vacuum state (see Figure ). A thermodynamic cycle starts from the molecule in a vacuum. Then, this molecule is stripped of its LJ and Coulomb interactions (ΔG1) and placed in the environment of interest, here a zeolite framework or a box of water molecules (ΔG2). This comes at an energy cost of zero (ΔG2 = 0), since no interaction between the molecule and the environment is present. The LJ and Coulomb interactions between the molecule and its environment are then gradually turned on, controlled by the scaling parameter λ, yielding (ΔG3). Since the sum of all Free Energies in a thermodynamic cycle is zero, ΔGads and ΔGsolv can be obtained from ΔG1 + ΔG3 in the respective thermodynamic cycle. Figure : Schematic depiction of both thermodynamic cycles used in the Free Energy Perturbation simulations.