In this study, we also re-crystallised CC21 from CH2Cl2 by slowly evaporating a saturated solution at room temperature. By comparison, the crystalline material isolated from CH2Cl2 was activated at 363 K under a dynamic vacuum before being analysed by single crystal and powder X-ray diffraction (PXRD). After activation under these conditions, we determined the structure of a new phase, CC21α, which is structurally related to CC21•CHCl3•MeOH but has a unit cell volume that is 15% smaller (SI, Table ) due to a denser packing of CC21 molecules. Notably, the PXRD pattern for the activated bulk sample crystallised from CH2Cl2 matches the simulated PXRD of CC21α (SI, Figure ), and we used this sample for N2 gas sorption analysis at 77.3 K (SI, Figure ). CC21α was found to adsorb 11.1 mmol g -1 of N2 at 1 bar and 77.3 K, and has a Brunauer-Emmett-Teller (BET) surface area of 699 m 2 g - 1 . PXRD data recorded post gas sorption analysis revealed that CC21α did not change structure during this measurement (SI, Figure ), indicating that the bulky isopropyl groups do not affect the stability of the activated material. This data also proves that CC21 is shape persistent in the solid state and retains its cavity in the absence of solvent. Computational assessment of the porosity of the obtained crystal structure suggests that channels through the structure are approximately the size of an N2 molecule, which allows for nitrogen adsorption (SI, Figure ).