Abstract
Porous organic cages have emerged over the last 10 years as a subclass of functional microporous materials. However, among all of the organic cages reported, large multicomponent organic cages with 20 components or more are still rare. Here, we present an [8 + 12] porous organic imine cage, CC20, which has an apparent surface area up to 1752 m2 g–1, depending on the crystallization and activation conditions. The cage is solvatomorphic and displays distinct geometrical cage structures, caused by crystal-packing effects, in its crystal structures. This indicates that larger cages can display a certain range of shape flexibility in the solid state, while remaining shape persistent and porous.
Highlights
Porous organic cages (POCs) are discrete polymacrocyclic molecules that contain a permanent, guest-accessible intrinsic cavity and that are porous to guests such as gases in the solid state
In contrast to extended porous frameworks, such as metal−organic frameworks (MOFs)[19] and covalent organic frameworks (COFs),[20,21] the permanent porosity of organic cages is mainly attributed to the intrinsic cavities present in these discrete, shape-persistent molecules
CC20 was obtained by the self-assembly of 8 molecules of 2hydroxy-1,3,5-triformylbenzene (HO-TFB) with 12 molecules of cis-1,3-CHDA
Summary
CC20 was obtained by the self-assembly of 8 molecules of 2hydroxy-1,3,5-triformylbenzene (HO-TFB) with 12 molecules of cis-1,3-CHDA. The as-crystallized P1 CHCl3/MeCN phase was carefully activated by initially exchanging the crystallization solvent with n-pentane and by heating this P1 n-pentane solvate at 30 °C under vacuum After activation using these conditions, we found that this phase performed better in terms of structural stability and it remained crystalline after gas-sorption analysis, according to PXRD measurements (Figure S14). Differences were observed between the simulated PXRD patterns of the Im n-pentane solvate and the P1 solvates, in comparison to the PXRD patterns recorded after desolvation and gas sorption analysis, indicating that the cage structures transform further during these processes (Figures S19 and S20) This is likely due to changes in the shape of CC20 upon desolvation and/or reorientation of the cages in the crystal lattice. This could potentially allow the application of this cage for molecular sensing.[13]
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