Chiral self-sorting and guest recognition of porous aromatic cages

Abstract

The synthesis of ultra-stable chiral porous organic cages (POCs) and their controllable chiral self-sorting at the molecular and supramolecular level remains challening. Herein, we report the design and synthesis of a serial of axially chiral porous aromatic cages (PAC 1-S and 1-R) with high chemical stability. The theoretical and experimental studies on the chiral self-sorting reveal that the exclusive self-recognition on cage formation is an enthalpy-driven process while the chiral narcissistic and self-sorting on supramolecular assembly of racemic cages can be precisely regulated by π–π and C–H…π interactions from different solvents. Regarding the chemical stability, the crystallinity of PAC 1 is maintained in aqueous solvents, such as boiling water, high-concentrated acid and alkali; mixtures of solvents, such as 1 M H2SO4/MeOH/H2O solution, are also tolerated. Investigations on the chiral sensing performance show that PAC 1 enables enantioselective recognition of axially chiral biaryl molecules.

Porous organic cages for gas separations

“…44 Since then, there has been a rapid increase in the number of POCs with different topologies, shapes, and surface areas, attracting significant attention over the past decade. 45–73 The common methods used to synthesize POCs can be categorized into two types: irreversible bond formation and reversible bond formation, which mainly include several condensation reactions. 20 Both methods have been extensively reviewed in recent publications.…”

Engineering UiO-68-Typed Homochiral Metal–Organic Frameworks for the Enantiomeric Separation of Fmoc-AAs and Mechanism Study

“…Chirality is an essential feature of various life processes. As chiral compounds get increasingly paramount in the fields of life sciences, pharmaceuticals, and food additives, the demand for chiral compounds is growing explosively. − At present, most of the synthetic chiral substances are racemates, and their two enantiomers may have completely different biological activities and pharmacological effects. − As a consequence, for the application of almost all racemates, it is imperative to seek effective enantiomeric resolution. − Nonetheless, owing to the dramatic similarity of the physicochemical properties of two enantiomers, enantiomeric separation has always been a difficult point in the fields of separation science, chemistry, and pharmacy. , In the past few decades, extensive efforts have been made to develop chiral porous materials for efficient enantiomeric separation. − Usually, enantioselective separation using chiral porous materials as adsorbents requires tailored and diverse chiral pore environments to efficiently interact with chiral substrates. ,, In recent years, homochiral metal–organic frameworks (HMOFs) with open pores/channels have drawn great attention for separation of chiral molecules due to their diversity in structure and pore size, tailored chiral pore environments, and selective adsorption affinity, enabling strong interactions with chiral substrates. − An excellent HMOF adsorbent to qualify for enantiomeric separation targets should at least simultaneously possess three features: (a) robust structure with high stability, (b) open and accessible pores, and (c) chiral environment with binding sites. Nevertheless, most of the HMOFs reported have weak chemical stability and small cavity size, which immensely limits their practical applications. − Therefore, the design and synthesis of HMOFs with excellent stability and large cavities lined with binding sites is the key to develop advanced enantioselective separation materials.…”

Chiral Self‐Sorting in Pd6L12 Metal‐Organic Cages

“…The former involves reversible bond-forming organic reactions under thermodynamic control, wherein a significant control over the choice of chiral selfsorting outcome has been established in higher-order complex structures. [4][5][6][7] Differently functionalized ligands, such as bidentate catechols, [8,9] 2,2-bipyridines [10] and imino-2-pyridines [11][12][13] with octahedral metal centers, and monodentate bis-pyridines with square-planar Pd(II) ions were examined with a later approach. [14][15][16][17][18][19] Among them, a racemic mixture of monodentate bis-pyridyl ligands and Pd(II) to form [Pd n L 2n ] 2n + -cage molecules is a crucial one.…”

“…Such chiral self‐sorting has been examined through two distinct options: dynamic covalent chemistry and coordination‐driven self‐assembly. The former involves reversible bond‐forming organic reactions under thermodynamic control, wherein a significant control over the choice of chiral self‐sorting outcome has been established in higher‐order complex structures [4–7] . Differently functionalized ligands, such as bidentate catechols, [8,9] 2,2‐bipyridines [10] and imino‐2‐pyridines [11–13] with octahedral metal centers, and monodentate bis‐pyridines with square‐planar Pd(II) ions were examined with a later approach [14–19] .…”