Enantiomerically enriched, polycrystalline molecular sieves

Abstract

Zeolite and zeolite-like molecular sieves are being used in a large number of applications such as adsorption and catalysis. Achievement of the long-standing goal of creating a chiral, polycrystalline molecular sieve with bulk enantioenrichment would enable these materials to perform enantioselective functions. Here, we report the synthesis of enantiomerically enriched samples of a molecular sieve. Enantiopure organic structure directing agents are designed with the assistance of computational methods and used to synthesize enantioenriched, polycrystalline molecular sieve samples of either enantiomer. Computational results correctly predicted which enantiomer is obtained, and enantiomeric enrichment is proven by high-resolution transmission electron microscopy. The enantioenriched and racemic samples of the molecular sieves are tested as adsorbents and heterogeneous catalysts. The enantioenriched molecular sieves show enantioselectivity for the ring opening reaction of epoxides and enantioselective adsorption of 2-butanol (the R enantiomer of the molecular sieve shows opposite and approximately equal enantioselectivity compared with the S enantiomer of the molecular sieve, whereas the racemic sample of the molecular sieve shows no enantioselectivity). chirality | zeolite | asymmetric catalysis | chiral adsorption

Influence of Flexibility on the Separation of Chiral Isomers in STW‐Type Zeolite

“…[17] The increasing degree of influence that intrinsic flexibility might have on selective behaviour leads to the question of how to approacht hesei ssues computationally.A lthough computing flexibility for the systems under study is currently effec-tive and couldp rovide am ore realisticv iew of the further separation process, it is still very expensive in terms of computational cost. The static lattice vibration around the equilibrium positiono ft he all-silicaf ramework of right-handedS TW smoothst he surface of the structure but keeps the adsorption sites that select (R)-2P over (S)-2P.L attice vibration is greater for STW-SiGe due to the presence of germanium atoms.…”

“…Among them, STW is ar ecently discovered zeolite that was first synthesised as ag ermanosilicate zeolite called SU-32. [17] Aw idespread idea is that chiral recognition is led by the confinement of the molecule inside the pores or channels of the materials. Later,a differents ynthetic strategy afforded ap ure-silica zeolite with the same STW framework type, [15] knowna sH PM-1 zeolite, which exhibitst he high thermala nd hydrothermals tability of silica materials.…”

Machine-learning approach to the design of OSDAs for zeolite beta

“…In this search, our procedure consisted of first designing putative small, achiral “monomer” OSDAs and then finding suitable chiral linkers to dimerize these (18). We here use these monomers for training a neural network.…”

“…In the past, we have successfully built upon this observation to use structure-based molecular design to obtain OSDAs for several zeolites (15–17), including a chiral OSDA leading to an enantiomerically enriched zeolite STW (18). The methods we have applied in these efforts include algorithms both for de novo design (19, 20) and virtual combinatorial chemistry (21), as well as virtual screening of selected sets of available compounds.…”

Analysis of stereoisomers of chiral drug by mass spectrometry

“…For example, (8R,8′R,7′S)-lyoniresinol enantiomer is strongly bitter whereas (8R,8′R,7′S)-lyoniresinol is tasteless 3 ; the S-enantiomers of 4-mercapto-2-hexanone and 4acetylthio-2-hexanone have more fruity and pleasant notes than the R-enantiomers. 5,6 There are several methods for chiral analysis, involving high-performance liquid chromatography (HPLC), gas chromatography (GC), supercritical fluid chromatography (SFC), thin-layer chromatography, and capillary electrophoresis (CE). 5,6 There are several methods for chiral analysis, involving high-performance liquid chromatography (HPLC), gas chromatography (GC), supercritical fluid chromatography (SFC), thin-layer chromatography, and capillary electrophoresis (CE).…”