[EMIM][CF3SO3]@CuBTC, there is an endothermic peak at ~ 330 °C, however, this reaction strongly overlaps with thermal decomposition. In [BMIM][PF6]@CuBTC this overlap appears to be even stronger, with the transition (if any) shifted even further to higher temperature (visible only as a weak shoulder in the primary decomposition peak). In both cases, while we cannot exclude the possibility that an endothermic phase transition similar to the one reported here for