As previously reported band shifts may indicate the redistribution of the electron density over the paddle-wheel unit following IL incorporation. Consistent with previous experimental and computational studies on the interactions between ILs and CuBTC, observed down-shifts in ν(Cu˗O) bands around 440 cm -1 indicate softening of the Cu˗O interaction. Conversely, the Cu˗Cu interaction becomes more rigid, with a blue-shift of the band at around 180 cm -1 upon IL incorporation (observed ex situ, i.e., in the spectrum of the low-temperature, distorted IL@CuBTC). These variations remain stable within the observed number of thermal cycles. In situ Raman spectroscopy performed during heating corroborates these observations (Figure ); it confirms that the softening transition occurs at a temperature near 190 °C (given the simultaneous laser interaction, we refrain from a more quantitative interpretation of the in situ Raman data at this point), recovering the CuBTC structure.