It can be inferred from these observations that the behaviour of co-adsorbed 5-FU and water in the zeolite pores is strongly impacted by the Brønsted acidity of the framework protons. It is therefore interesting to compare this behaviour to that of 5-FU in aqueous solution. For this purpose, additional AIMD simulations were run for a box containing one 5-FU and 256 H2O molecules, considering three different starting configurations. The RDFs computed from these trajectories, shown in Figure , provide no indications for protonation of 5-FU oxygen atoms or deprotonation of nitrogen atoms, in other words, the neutral tautomer shown in Figure is stable in aqueous solution. This corroborates that the proton(s) that the zeolite provides are responsible for the proton transfers between 5-FU and its environment observed in the AIMD simulations.