This mechanical response occurs in about the same temperature range as the DSC endotherm, given the experimental variations between TMA and DSC observations. It indicates structural flexibility in CuBTC induced by IL, leading to a recovery of the CuBTC structure when a sufficiently high temperature is reached (see Figure ), unlike the parent CuBTC which is not known to exhibit similar breathing effects. Evidence of cooling rate-dependence on the expansion event is shown in Figure for IL@CuBTC, cooling at 10 K⸱min -1 and at 1 K⸱min -1 . Similar to DSC observations, the contraction reaction shifts to higher temperature with lower cooling rate, indicating kinetic activation in the supercooled state. To further investigate the potential occurrence of similar reversible ordering transitions in a wider range of MOF-IL combinations, we fabricated other IL@MOF composites using alternative constituents as the FeBTC (Basolite® F300, iron 1,3,5-benzenetricarboxylate). FeBTC exhibits the structure of MIL-100(Fe) (Matériaux de l′Institut Lavoisier), with Fe-µ 3 -oxo-clusters that are bridged by BTC linkers, compared to the Cu-Cu paddlewheel units in CuBTC.