Based on these synthetic screens, two azobenzene-covalent cages (ACC) were discovered with high conversion: ACC-1 formed from the tetratopic aldehyde with CHDA in a Tet 3 Di 6 topology, and ACC-2 formed from the ditopic aldehyde with TREN as a Tri 2 Di 3 capsule (Fig. ). Single crystal structures were grown directly from the reaction solutions by vapour diffusion with ethanol, confirming the cage topologies (SCXRD ACC-1 Fig. , ACC-2 Fig. ). Isolation of the bulk material found that ACC-1 retained no crystallinity, showing only amorphous character by PXRD (Fig. ), and ACC-2 produced a crystalline sample that resembled the simulated powder pattern from the SCXRD data (Fig. ). We next explored the possible range of accessible photoisomers for these two cages using computational modelling. For each cage containing three diazene moieties, four species are possible: fully trans (EEE), partially isomerized (EEZ and EZZ), and fully cis (ZZZ). Models were assembled for each of these isomers for both ACC-1 and ACC-2, and longer MD conformer searches performed and the relative formation energies and internal cavity diameters compared using DFT calculations at the PBE/TZVP+D3 level (Fig. ). In both cases, the relative energy of the ZZZ-configuration was the highest, and the EEE-configuration was the lowest. The intermediate structures follow this trend, with each additional Z-isomer resulting in a higher relative energy. By comparison, for a triazomacrocycle reported by the relative energy of the fully cis-isomer was approximately 106 kJ mol -1 higher than the fully trans-isomer, and they were able to achieve 73% isomerization. The internal cavity diameters of both cages were also calculated from these computational models. ACC-1 has a larger internal cavity than ACC-2 in all isomeric states. When in the fully transconfiguration (EEE), ACC-1 has an internal spherical cavity diameter of 4.4 Å, which increases to 6.4 Å when in the ZZZ-configuration. The change in cavity size is not simply monotonic with isomerization, and there is a small decrease in cavity size between the EEZ-and EZZ-forms (5.5 to 5.4 Å). By contrast, there is predicted to be a complete loss of the internal cavity for ACC-2 in its EZZ-and ZZZconfigurations, although there is an initial increase in spherical cavity diameter from EEE to EEZ of 2.2 to 2.4 Å. As well as the size, as can be seen from Figure , the shape of the cavity also changes considerably. In principle, both the size and shape could be exploited to allow small gas molecules to be selectively adsorbed and desorbed; unfortunately, it was found that neither of the two cages could adsorb N2 (77 K), CO2 or CH4 (273 K) as the EEE-isomer in the bulk amorphous phase (Fig. ), which is likely due to a lack of an interconnected pore network in the amorphous state when compared to the crystal packing observed in the SCXRD for cage solvates, particularly for the Tet 3 Di 6 species (Fig. ).