tool, (Figure ). DED (ρΔ) was generated with the USF Chimera software showed residual electron density in the cavities, confirming the presence of guest molecules in the pores (Figure ). Further Pawley refinements of the PXRD patterns recorded at 27, 131 and 225 °C were carried out to explore the potential structural phase transitions upon heating. At 27 °C the structure fits well using the Fm-3m space group (Figures S11-13, Table ), whilst at 131 °C multiple peaks appear and a good fitting using a cubic space group is not possible. Decreasing into a subgroup with a lower symmetry a successful fitting was found using the tetragonal space group P-4n2 (Figure , Table ). The former symmetry was recovered after the transition at 225 °C (Figure , Table ).