From the above results, the most counterintuitive outcome is that the mixture of mbimH and eimH leads to a material with SOD topology, despite not being this topology the most stable one for pure mbimH or pure eimH in any of the three metals evaluated. In fact, previous attempts to combine mbimH with another ligand has resulted in the formation of JUC-160 and Zn(2mbim)0.28(5mbim)1.72 with GIS and ykh topologies, respectively. Thus, we further investigated this from a theoretical point of view. Density functional theory calculations were performed for ZIF-8, ZIF-67 and MUV-3 in several ligand compositions to assess phase stability (see the SI for computational details). Minimum-energy crystal structures for the pure-and mixed-ligand MOFs at the PBEsol level present cell parameters in good accord with the experimental data (Tables S1, S3 and S4). Theoretical calculations predict the most stable phases for each pure-ligand ZIF to be SOD for mim, dia for mbim, and qtz for eim (Table ), in agreement with the polymorphs found experimentally for the zeolitic framework series. Figure displays the relative phase energy as a function of the eim:mbim ligand mixing ratio in the case of ZIF-8 (see Figure for Co-based ZIF-67 and Figure for Fe-based MUV-3). Upon increasing the mbim fraction, the qtz topology rapidly destabilizes up to an energy difference of > 1 eV when reaching 100% mbim with respect to pure-eim ZIF-8. This destabilization can be rationalized by the large steric hindrance promoted through the introduction of bulkier mbim ligands with respect to eim in the relatively small qtz unit cell, which suffers a 45% cell expansion in going from pure-eim to pure-mbim (Table ). In contrast, ligand substitution barely affects phase stability in dia topology, which is computed more stable than qtz for eim:mbim ratios of > 0.25 (Figure ). Interestingly, the SOD topology, which is not the most stable phase either in pure-eim or pure-mbim MOFs, is predicted the lowest in energy upon ligand mixing, especially at a 2:1 eim:mbim composition, in the three ZIFs (Figure and S25-S26). A careful inspection of the crystal structure evidences for the 33% mbim fraction an effective match of the two eim and one mbim ligands at the SOD six-membered ring gate (Figure ), along with additional ethyl•••benzene CH•••π interactions between eim and mbim (Figure ). On the other hand, the addition of further mbim leads to an increased steric hindrance between benzene rings that destabilizes the SOD topology in favour of dia, for 100% mbim (Figure , S25-S26).