The studied hybrid coordination network crystal (Co(hmba) 3[CoBr4]) studied in the present work was synthesized following the procedure of Ref. Ref. and deposited in the Cambridge Crystallographic Data Centre (CCDC) with deposition number 120454) The unit cell structure of Co(hmba)3[CoBr4] (crystallizing in the P-1 space group with two unique Co sites, namely an octahedron and a tetrahedron) is presented in Figure , while Figure highlights the (i) layer-like percolating network of Co and hmba-linkers and (ii) interpenetrating [CoBr4] 2--tetrahedra positioned in the vacancies of the layered network. Figure shows a single layer of the percolating hmba linkers and Co 2+ octahedra. Finally, Figure . Here, we demonstrate that the properties of these systems are highly sensitive to the water content. Figure shows differential scanning calorimetry heating scans performed in sealed Al crucibles for the pristine Co(hmba)3[CoBr4] crystal and glass with no or 7 wt% added water (i.e., ~4.6 water molecules per bridging cobalt atom, which is significantly below the content needed to fully dissolve the sample in water), respectively. Upon water addition, the melting transition clearly becomes broader as it occurs over a larger range of temperature and ends at a significantly lower temperature (right part of Figure ). This broadening may be due to the kinetics involved in the inhomogeneous distributing of added water in the crystalline powder prior to entering the molten state or a lowering of the melting enthalpy. Apart from melting, the glass transition temperature decreases significantly (left part of Figure ). The dependence of the melting peak temperature (Tm) and glass transition temperatures (Tg) on water content in the Co(hmba)3[CoBr4] system is shown in Figure . The increase in water concentration significantly lowers the melting temperature from ~110 °C to a constant value of ~70 °C at a water concentration of ~14 wt%, with no changes upon further water addition. To probe the universality of the effect of water on Tm and Tg, we also investigate the melting behavior of the Co(hmba)3[Co(SCN)4] and Mn(hmba)3[MnBr4] networks. As presented in Figure , we find a very similar effect of decreasing Tm with increasing water content in these systems as that found for Co(hmba)3[CoBr4],