A 1:1 mixture of the three possible binary combination of ligands results in crystalline solids after 48 h upon reaction with ZnO, cobaltocene or ferrocene at 250 ºC. The phase purity and the presence of only one polymorph was determined using Xray powder diffraction (XRPD), confirming the homogeneity of the crystals obtained during the synthesis and discarding a possible segregation of phases, a common situation when using mixtures of ligands. In eight of the nine possible scenarios, we managed to obtain mixed-ligand structures with a SOD topology (Figure ). Scanning electron micrographs (SEM) show the well-defined morphology of all of the mixed-ZIFs (see Figure and section 2.6). In only one situation, when using a mixture of mimH and eimH with Fe(II), a qtz framework with only one of the ligands (eimH) was obtained (see Figure ). The presence of two ligands was confirmed by solid state 1 H NMR spectroscopy (Figure ) in the diamagnetic samples (ZIF-8-mimb, ZIF-8-eimb and ZIF-8-eimi). In addition, all the eight mixed-ligand samples were digested in D2O and deuterated trifluoroacetic acid, and then evaluated by H NMR spectroscopy (see Section S2.4). In all cases, we observed an approximate 2:1 ratio in the ligands, with a minor component of the bulkier imidazole derivative. Interestingly, it is possible to slightly modify the final ratio by adjusting the proportion in the synthesis. Nevertheless, we have found an upper limit of ca. 70 % and a lower limit of ca. 50% for 2eimH and 2mimH, respectively. Importantly, large crystals suitable for X-ray single crystal diffraction were obtained for two compounds, namely MUV-3mimb and MUV-3-eimb. Structural analysis reveals that both compounds are isoreticular with MUV-3 (and ZIF-8 and ZIF-67), with similar crystal cell parameters and Fe-N distances (see Table ), being slightly larger than MUV-3. In addition, the angle θ between the imidazoles and the 4MR plane, as previously defined, are similar in the three structures: 74.4°, 75.9° and 77.4° for MUV-3, 21 MUV-3-mimb and MUV-3-eimb, respectively. Interestingly, despite starting with a 1:1 ratio between the two ligands, their occupancy was included in the refinement, resulting in both cases in a 70:30 ratio (mi:mb or ei:mb for MUV-3-mimb and MUV-3-eimb, respectively), as also found by 1 H NMR spectroscopy (see S2.4). The confirmed mixed-ligand Fe(II) structures present higher thermal stability (Figure ) compared to MUV-3 as a result of the incorporation of mbimH in the structure.