The phase transition underlying the latent heat capacity of the IL@MOF composite is not a melting, as shown previously for MOF and IL@MOF composites (solid-to-liquid) phase transition. The melting point of the bare IL is -16 °C; the MOF alone decomposes before melting. Other than what has been observed for certain IL@MOF combinations, the presence of the IL does not facilitate melting of CuBTC. Instead, the current phase transition involves a reversible change in IL ordering at the MOF-IL interface. To investigate the associated structural changes governing this transition, we initially performed variable-temperature XRD (VT-XRD) analysis on CuBTC and on the IL@CuBTC composite, shown in Figure . These scans used a temperature program identical to the one used for DSC analysis. Ref. .