Small molecule, large surface area: A rigid triptycene derivative self‐assembles by hydrogen bonds to a porous crystal with one‐dimensional channels of about 14 Å diameter. Solvents in the channels can be removed to generate an extrinsic porous material with a specific BET surface area of 2796 m2 g−1. Furthermore, gases can be selectively adsorbed within the pores at 1 bar.

Recently, porous organic cage crystals have become a real alternative to extended framework materials with high specific surface areas in the desolvated state. Although major progress in this area has been made, the resulting porous compounds are restricted to the microporous regime, owing to the relatively small molecular sizes of the cages, or the collapse of larger structures upon desolvation. Herein, we present the synthesis of a shape-persistent cage compound by the reversible formation of 24 boronic ester units of 12 triptycene tetraol molecules and 8 triboronic acid molecules. The cage compound bears a cavity of a minimum inner diameter of 2.6 nm and a maximum inner diameter of 3.1 nm, as determined by single-crystal X-ray analysis. The porous molecular crystals could be activated for gas sorption by removing enclathrated solvent molecules, resulting in a mesoporous material with a very high specific surface area of 3758 m(2)  g(-1) and a pore diameter of 2.3 nm, as measured by nitrogen gas sorption.

No abstract

The synthesis of various periphery-substituted shape-persistent cage compounds by twelve-fold condensation reactions of four triptycene triamines and six salicyldialdehydes is described, where the substituents systematically vary in bulkiness. The resulting cage compounds were studied as permanent porous material by nitrogen sorption measurements. When the material is amorphous, the steric demand of the cages exterior does not strongly influence the gas uptake, resulting in BET surface areas of approximately 700 m(2)  g(-1) for all cage compounds 3 c-e, independently of the substituents bulkiness. In the crystalline state, materials of the same compounds show a strong interconnection between steric demand of the peripheral substituent and the resulting BET surface area. With increasing bulkiness, the overall BET surface area decreases, for example 1291 m(2)  g(-1) (for cage compound 3 c with methyl substituents), 309 m(2)  g(-1) (for cage compound 3 d with 2-(2-ethyl-pentyl) substituents) and 22 m(2)  g(-1) (for cage compound 3 e with trityl substituents). Furthermore, we found that two different crystalline polymorphs of the cage compound 3 a (with tert-butyl substituents) differ also in nitrogen sorption, resulting in a BET surface area of 1377 m(2) g(-1), when synthesized from THF and 2071 m(2) g(-1), when recrystallized from DMSO.

Interior decorating: A post‐synthetic method allows porous organic cage compounds to be prepared with functionalized interior cavities. The approach produces modified cage compounds in quantitative yield and opens the possibility of preparing organic alloys with different functionality. The solution‐based technique shows the advantage of solubility, an inherent property of porous materials derived from discrete organic molecules.