In situ VT-XRD scans performed during cycling are presented in Figure . In pure CuBTC, the crystal structure remains stable during heating and cooling within the observed temperature window (Figure ). This is also corroborated by Pawley refinements of the structure using the space group Fm-3m (225) (Figures S7-S10, Table ). However, for IL@CuBTC, there is a distinct structural transition visible upon heating and, reversibly, upon cooling (Figure and).