To gain a deeper insight into the energetics of phase change, we compared the magnitude of ΔU ‡ act against the formation enthalpy of the MOF (ΔHf). As ΔHf represents the energetic cost of entirely 170 decomposing the framework into its constituent terephthalate and Zn4O components, it provides a maximum value for framework stability -ΔU ‡ act values above ΔHf would signify that the MOF is more likely to fully decompose rather than successfully activate. The heat of formation, ΔHf, of IRMOF-1 has been estimated through experimental and computational methods to be -25 and -40 kJ/mol(Zn), respectively. As these values are orders of magnitude higher than the calculated ΔU ‡ act in IRMOF-1, 175 collapse caused by acetonitrile removal is not thermodynamically favoured. Instead, some aspect of the phase transition must induce collapse.