The structures of the six all-silica zeolites (BEA, FAU, AFI, IFR, MOR, CFI frameworks, represented by the framework type codes [FTC] assigned in the structure database of the International Zeolite Associations IZA ) are the same as in previous work (Table ). Sources of the experimental structure data and the corresponding cell parameters are given in the ESI (Table ). As described in more detail in previous work, short AIMD simulations were run for all zeolite structures (NVT ensemble, T = 298 K, timestep 1 fs, total duration 12.5 ps). The average structure from the production stage of the AIMD simulation (10 ps) was then subjected to a symmetry search and DFT-optimized. atom and one charge-balancing proton per unit cell/1×1×3 supercell, respectively. Due to the low amount of framework Al atoms, the same (experimental) cell parameters as for the allsilica systems were used. As there is only one type of T site in FAU, only one Al position was considered. Structure models with protons attached to each of the four surrounding oxygen atoms were constructed and DFT-optimized. Among the four models, the H@O2 case was found to be lowest in energy (Table , the labelling of T and O atoms in FAU and MOR follows the IZA database ). However, the H@O2 proton points across a 6MR in an inaccessible area of the structure (the 6MR links a double six-membered ring and a sodalite cage, both of which are inaccessible for most guest molecules). In the H@O1 model, which is only 5 kJ mol -1 higher in energy (second lowest), the proton points into a 12MR, thus being accessible to guests accommodated in the supercages that are linked by these windows. This is also the most occupied proton site according to experimental investigations on protonated FAU samples with lower Si/Al ratios. The H-FAU(H@O1) model was hence used in all further calculations. In MOR, the increased complexity of the framework, with 4 non-equivalent T sites in the aristotype, is exacerbated by the symmetry reduction to space group 𝑃2 2 2 in the structure model obtained from the AIMD simulations. To limit the number of possible Al+H arrangements, only those cases where the proton points (approximately) into the 12MR channels were considered: Under this constraint, the framework proton can be attached to the O1, O4, O7, or O10 atoms, and the Al atom, which should be at a neighboring T site, can be located at the T1, T2, or T4 sites. Due to the aforementioned symmetry reduction, some of these sites are split into up to 4 non-equivalent sites, resulting in a total of 22 distinct arrangements. Models for these arrangements were constructed in a 1×1×3 supercell of the MOR unit cell and DFT-optimized. All models are listed in the ESI (Table and Figure ).