It is clear that calculations addressing the individual adsorption of either TCS molecules or H2O clusters can only deliver indirect insights into the relative affinity towards the two species. In particular, the magnitude of the adsorption energy of a (H2O)N cluster that competes with TCS will depend on the cluster size, limiting the quantitative interpretation. To obtain insights into the co-adsorption of TCS and water, the simultaneous interaction of both species with FAUand MOR-type zeolites was investigated. For all-silica FAU and MOR, an approach based on DFT optimizations was employed: Starting from DFT-optimized low-energy TCS@Zeo and 8H2O@Zeo configurations, the other species (eight H2O molecules/one TCS molecule) was added using MC simulations. After a simulated annealing of the MC snapshots, five configurations for each case were extracted and DFT-optimized. Figure shows the Boltzmann-averaged adsorption energies for the 8H2O@(TCS@Zeo) and TCS@(8H2O@Zeo) complexes. First of all, it is worth noting that the adsorption energies are very close, regardless of whether H2O molecules were added to a TCS@Zeo complex or vice versa. Second, the total adsorption energies are more negative than the sum of the individual adsorption energies computed for TCS and water, indicating that H2O-TCS interactions during co-adsorption of both species are, overall, attractive. The difference is larger for FAU than for MOR, which can be understood when looking at exemplary low-energy configurations (Figure ): In the spacious cages of FAU, the water molecules not only form hydrogen bonds to each other and to framework oxygen atoms, but also to the hydroxyl group of TCS, which simultaneously acts as hydrogen bond donor and acceptor. In MOR, the water cluster occupies a different channel section than the TCS molecule, limiting the possibility of guest-guest interactions. For the protonated zeolites, it is most interesting to elucidate what happens to a TCS molecule that is adsorbed at a framework proton in the presence of water at finite temperature. To investigate this, 8H2O@(TCS@Zeo) configurations were generated for H-FAU and H-MOR using MC simulations. Subsequently, three AIMD simulations starting from different MCgenerated configurations were run for each zeolite. In these cases, the first 2.5 ps of the trajectories were not discarded, but included in the analysis, since the most significant structural changes were typically found to occur during the very initial stages of the simulations.