As discussed above, the DFT-optimized lowest-energy TCS conformer possesses an intramolecular hydrogen bond from the hydroxyl group to the central oxygen atom. This bond remains present in all of the lowest-energy TCS@Zeo complexes, and an evaluation of the hydrogen bond distances reveals a certain shortening of the distance 𝑟(H As the adsorption energies are not correlated with the hydrogen bond distance, it can be concluded that hydrogen bonds make only a minuscule contribution to the total zeolite-TCS interaction. To illustrate typical adsorption complexes with and without hydrogen bonds, the lowest-energy TCS@AFI and TCS@IFR configurations are visualized in Figure . ). The adsorption energies are distinctly more negative than for the corresponding all-silica zeolites, with the differences amounting to -31 kJ mol -1 (corresponding to a change by -25%) for FAU and to -36 kJ mol -1 (-23%) for MOR. This increase in interaction strength can be straightforwardly attributed to the formation of a hydrogen bond from the framework proton to the TCS Oh atom, visualized in the lowestenergy configurations shown in Due to steric reasons, the hydroxyl group of TCS does not form any additional hydrogen bonds to framework oxygen atoms in the lowest-energy TCS@H-FAU/H-MOR complexes.