Reticular Chemistry in the Construction of Porous Organic Cages

Abstract

Reticular chemistry offers the possibility of systematic design of porous materials with different pores by varying the building blocks, while the emerging porous organic cage (POC) system remains generally unexplored. A series of new POCs with dimeric cages with odd−even behaviors, unprecedented trimeric triangular prisms, and the largest recorded hexameric octahedra have been prepared. These POCs are all constructed from the same tetratopic tetraformylresorcin[4]arene cavitand by simply varying the diamine ligands through Schiff-base reactions and are fully characterized by X-ray crystallography, gas sorption measurements, NMR spectroscopy, and mass spectrometry. The odd−even effects in the POC conformation changes of the [2 + 4] dimeric cages have been confirmed by density functional theory calculations, which are the first examples of odd−even effects reported in the cavitand-based cage system. Moreover, the "V" shape phenylenediamine linkers are responsible for the novel [3 + 6] triangular prisms. The window size and environment can be easily functionalized by different groups, providing a promising platform for the construction of multivariate POCs. Use of linear phenylenediamines led to record-breakingly large [6 + 12] truncated octahedral cages, the maximum inner cavity diameters and volumes of which could be readily modulated by increasing the spacer length of the phenylenediamine linkers. This work can lead to an understanding of the self-assembly behaviors of POCs and also sheds light on the rational design of POC materials for practical applications.

Chiral Self‐sorting of Giant Cubic [8+12] Salicylimine Cage Compounds

“…[13i] The meso cage as well as the enantiopure cage were characterized by X-ray diffraction and are among the largest organic cages characterized by this method and the largest chiral ones.Gas sorption measurements revealed high specific surface areas of up to SA BET = 1487 m 2 g À1 (N 2 ,7 7K), av alue that has been rarely exceeded by other cages reported so far. [33,34,41] Interestingly,t he most crystalline sample displayed the highest specific surface area but the lowest selectivities,emphasizing that crystallinity and high degree of order does not necessarily lead to superior gas sorption properties. [41a, 42] Table 1: Summary of crystal structure derived properties and experimental gas sorption properties (BET derived surface areas, selectivities, gas uptakes and heats of adsorption) of the [8+ +12] cage compounds (P,M)-4_1 (precipitateformed during the reaction), (P,M)-4_2 (crystals grown from CHCl 3 ), (P)-4 and (M)-4.…”

“…(d in = 3.9 nm) [34] and the giant porphyrinic cages from Kimoon Kim and co-workers (d in = 4.3 nm). [35] Ther ectangular cage window is exceptionally large with as ize of approx.…”

Gas Storage in Porous Molecular Materials

“…The term “porous organic cages” (POCs) was first used in 2009 with the preparation of a series of tetrahedral imine‐linked cages that retained permanent porosity in the solid‐state upon solvent removal [42, 89] . Following this pioneering work, POCs have been investigated for host–guest encapsulation, molecular separations, and chemical sensing [30, 90, 91] . Although studies on gas separations have been explored, reports on the use of POCs for gas storage are limited.…”

Chiral Self‐sorting of Giant Cubic [8+12] Salicylimine Cage Compounds

“…[13i] The meso cage as well as the enantiopure cage were characterized by X-ray diffraction and are among the largest organic cages characterized by this method and the largest chiral ones.Gas sorption measurements revealed high specific surface areas of up to SA BET = 1487 m 2 g À1 (N 2 ,7 7K), av alue that has been rarely exceeded by other cages reported so far. [33,34,41] Interestingly,t he most crystalline sample displayed the highest specific surface area but the lowest selectivities,emphasizing that crystallinity and high degree of order does not necessarily lead to superior gas sorption properties. [41a, 42] Tabelle 1: Summary of crystal structure derived properties and experimental gas sorption properties (BET derived surface areas, selectivities,gas uptakes and heats of adsorption) of the [8+ +12] cage compounds (P,M)-4_1 (precipitateformed during the reaction), (P,M)-4_2 (crystals grown from CHCl 3 ), (P)-4 and (M)-4.…”

“…Forschungsartikel (d in = 3.9 nm) [34] and the giant porphyrinic cages from Kimoon Kim and co-workers (d in = 4.3 nm). [35] Ther ectangular cage window is exceptionally large with as ize of approx.…”