Even though the above calculations have established that the octahedral Al environment requires additional H2O molecules for stabilisation, the calculations including Al-coordinated 5-FU considered, in the first place, only the "bare" Aloct site without additional water molecules. This simplification is primarily motivated by the complications that would arise from an inclusion of non-coordinated water molecules in the calculation of the adsorption energy: In such a system, there is no straightforward way to disentangle different contributions to the total energy (framework-water, framework-5-FU, 5-FU-H2O, H2O-H2O), precluding an unambiguous decomposition that would allow to compute 5-FU adsorption energies. As detailed in 2.2, a total of six 5-FU@FAU_fwAloct_2Al configurations were optimised, which differ in the water molecule that was replaced by 5-FU and the coordination mode of 5-FU ("O2-on" vs. "O4-on").