Engineering chiral porous metal-organic frameworks for enantioselective adsorption and separation

Abstract

The separation of racemic molecules is of substantial significance not only for basic science but also for technical applications, such as fine chemicals and drug development. Here we report two isostructural chiral metal-organic frameworks decorated with chiral dihydroxy or -methoxy auxiliares from enantiopure tetracarboxylate-bridging ligands of 1,1 0 -biphenol and a manganese carboxylate chain. The framework bearing dihydroxy groups functions as a solid-state host capable of adsorbing and separating mixtures of a range of chiral aromatic and aliphatic amines, with high enantioselectivity. The host material can be readily recycled and reused without any apparent loss of performance. The utility of the present adsorption separation is demonstrated in the large-scale resolution of racemic 1-phenylethylamine. Control experiments and molecular simulations suggest that the chiral recognition and separation are attributed to the different orientations and specific binding energies of the enantiomers in the microenvironment of the framework.

NMR study of localization and mobility of 1‐phenylethanol enantiomers in homochiral metal‐organic sorbent Zn2(bdc)(S‐lac)(dmf)

“…The main results of the work are as follows: 13 C NMR chemical shifts do not show an obvious advantage of selective interaction of molecules guests. This allows to suggest existence of a synergetic mechanism for the selective sorption of molecule ( R )‐PhEtOH and ( S )‐PhEtOH with the sorbent. Activation molecular mobility of S ‐PhEtOH and R ‐PhEtOH clearly indicates that stabilization of the structure [Zn 2 (bdc)( S ‐lac)(dmf)]· S ‐PhEtOH is more preferable than stabilization of [Zn 2 (bdc)( S ‐lac)(dmf)]· R ‐PhEtOH, which corresponds to the hand‐in‐glove principle for guest molecules similar to that known for enzymes. A selective interaction of molecules on the surface of the enantiomers of [Zn 2 (bdc)( S ‐lac)(dmf)] complexes has been unexpectedly discovered. Interactions of chiral molecules on the surface of [Zn 2 (bdc)( S ‐lac)(dmf)] and related compounds are supposed to be the subject of further studies. …”

“…Many useful properties of homochiral MOFs are due to enantioselective recognition based on chiral recognition mechanisms of separated centers. Also, multiple chiral recognition sites are possible that can work synergistically to induce selective recognition . The calculated energies of intermolecular interactions in a porous framework and in different enantiomers vary from 1–5 to 32 kJ/mol depending on the host–guest system .…”

“…The calculated energies of intermolecular interactions in a porous framework and in different enantiomers vary from 1–5 to 32 kJ/mol depending on the host–guest system . However, understanding sorption and enantioselective recognition mechanisms requires the data on the mobility of guest molecules in matrices of sorbents rather than structural and energy characteristics only . As is known, solid‐state NMR can be used effectively to study guest–host interactions in different sorbents, in particular interaction of enantiomers in MOF (a clear example,).…”

Imparting amphiphobicity on single-crystalline porous materials

“…As an emerging class of porous materials with high single crystallinity, metal-organic frameworks (MOFs)161718, which feature amenability to design, high surface areas, tunable pore sizes and tailorable functionality, have recently been extensively investigated for applications in gas storage1920, separation2122, carbon capture2324, catalysis25262728, sensing2930 and so on (refs 31, 32, 33, 34). However, an issue for their wide applications in practice includes the performance under a variety of environments (for example, stability in humid conditions, interferences by organic vapours in the atmosphere35363738), which necessitate the sophisticated control of the surface wettability of MOFs.…”

Synthesis of Chiral Labtb and Visualization of Its Enantiomeric Excess by Induced Circular Dichroism Imaging

“…[3][4][5][6][7][8][9][10][11][12][13] Kim and co-workerss ucceeded in constructing ac hiral MOF by using enantiopure ligandsa nd reported the enantioselective guest adsorption and catalytic performance. It is of paramount importance to develop chiral-recognizable molecular systemsw hich show sophisticated multipointi nteractions toward the chiral molecules.…”