To complement the ab initio simulations and provide real space temperature-resolved structural information of the Co(hmba)3[CoBr4] hybrid coordination network system in both the crystalline, molten, and glassy states, we have performed in situ extended X-ray absorption fine structure (EXAFS) measurements (see raw data in Figure ). The Fourier-transformed extended X-ray absorption fine structure (FT-EXAFS) spectra are shown in Figure for both the pristine (Figure ) and hydrated (Figure ) systems in the crystalline (red), molten (green), and glassy states (blue). We note that the presented peaks of FT-EXAFS spectra are shifted by around -0.5 Å due to an uncorrected phase shift, which is a common feature in EXAFS data. In the water-free system, the cobalt environment features a bimodal distribution of bond lengths, with the shortest one corresponding to Co-O (below 2 Å) and the longer one to the Co-Br distance (above 2 Å). Upon heating to 140 °C, we find a decrease in the overall peak area of both the Co-O and Co-Br correlations, suggesting a decrease in the CNs and an increase in thermal disorder for both Co environments in the structure. We note that the simulations mainly showed breakage of the Co-O bonds, but this may reflect the general limits in terms of simulation time. Furthermore, we find that the Co-Br bonds appear to be reestablished when cooling into the glassy state, while the Co-O bonds appear to be permanently shortened and with a smaller CN (see Figure , blue curve). This is consistent with the persistent blue color from the [CoBr4] 2-centers observed in the optical absorption spectra (Figure ). Significant changes in the FT-EXAFS spectra are observed upon water addition to the Co(hmba)3[CoBr4] system (Figure ). First, considering the crystalline state with added water, the relative intensity of the Co-O to the Co-Br peak is significantly increased when adding water (see direct comparison in Figure ). This may be because water already affects the Co-O octahedra even before the system enters the molten phase. Now, upon heating to 140 °C (green curve in Fig. ), the local geometry of Co is altered, with significant changes in the coordination environments. An apparent trimodal distribution is observed, which we ascribe (from lowest to highest bond length) to Co-O(hmba), Co-O(water), and Co-Br bonds, respectively. This assignment agrees with the bond lengths of Co-O(hmba) and Co-Br as obtained from the ab initio simulations (Figure ) as well as with work showing that aquo-Co 2+ complexes generally exhibits bond distances around 2.1 Å, i.e., in between the two others. It is not possible to unambiguously ascribe this to a certain chemical species, but since the optical absorption results suggest that the [CoBr4] 2-centers remain largely intact (Figure ), we infer that oxygens from water (O(w) in Figure ) coordinate and partially replace hmba-oxygens, producing a signal that is partially overlapping with that of the Co-Br correlation. Notably, this is consistent with the fact that aquo-cobalt complexes typically exhibit Co-O bond distances of around 2.1 Å, that is, between those of Co-O(hmba) (~1.9 Å) and Co-Br (~2.5 Å). Furthermore, correlations in the initial Co-O(hmba) range of ~1.9 Å are found to be present in the hydrated glass structure, thus suggesting that Co atoms still coordinate to hmba in the hydrated sample (although at a lower CN).