Chiral Resolution using Supramolecular‐Templated Mesostructured Materials

Abstract

Chiral resolution using non-functionalized mesoporous particles is demonstrated for avariety of enantiomeric pairs.T his is achieved through the use of supramolecular templated silica materials prepared with guanosine monophosphate (NGM-1) and folic acid (NFM-1) which enable direct chiral transcription onto the surface of the mesopores after solvent extraction and post calcination of the template. The chiral selectivity and kinetics of the mesoporous materials are measured by circular dichroism (CD) spectroscopyo n adsorbed molecules with different affinities for the pore surface.N GM-1 and NFM-1 have opposite enantiomeric selectivity for enantiomeric pairs.T hese results significantly increase the potential of mesoporous materials for chiral separation and enantiomeric catalysis.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.

Equilibrium and Kinetic Study of l- and d-Valine Adsorption in Supramolecular-Templated Chiral Mesoporous Materials

“…It is especially intense in c NGM-1( l -valine) and c NFM-1( d -valine) samples after adsorption of the amino acid with an initial concentration of 300 mM (see also Supplementary Materials, Figure S3 ). The peak is less prominent for adsorption of the opposite enantiomers at a similar starting concentration, indicating a higher adsorption capacity within the mesoporous structure and corresponding to the same enatioselectivity observed in our previous work, i.e., d -valine for c NGM-1 and l- valine for c NFM-1 [ 22 ]. Analysis of the crystallite size estimated from the Scherrer equation suggests valine crystals to be between 60 and 80 nm when the initial concentration is below 300 mM (see Table S1, Supplementary Materials ).…”

“…The synthesis of mesoporous NGM-1 employed here is similar to that reported previously [ 22 ]. Initially, guanosine 5′-monophosphate disodium hydrate (GMP, 0.60 g, 0.34 mmol) was dissolved in H 2 O (21 mL, 239.55 mmol, MillQ) in a Teflon vessel.…”

“…The synthesis of mesoporous NFM-1 employed here is similar to that reported previously [ 22 ]. Folic acid (FA, 0.23 g, 0.18 mmol) and H 2 O (35 mL, 341.4 mmol, MillQ) were combined with a magnetic stir bar in a Teflon vessel, and the mixture was left to stir (400 rpm) for 1 h at room temperature.…”

“…Material synthesis protocols and characterisation for c NGM-1 and c NFM-1 have been published previously [ 22 ] and are based on the use of supramolecular templates in coordination with a co-structure directing agent [ 35 ]. Figure S1 (Supplementary Materials) shows powder XRD patterns for both calcined mesoporous materials used in the present study, showing well-ordered mesostructures that can be indexed from a hexagonal unit cell.…”

“…We have recently developed chiral mesoporous silica materials prepared in the absence of surfactants, using chiral supramolecular templates, guanosine monophosphate (to produce nanoporous guanosine monophosphate material-1 (NGM-1)) and folic acid (to produce nanoporous folic acid material-1 (NFM-1)) [ 22 , 23 ]. Whilst designing these materials in a wide range of mesopore sizes remains a challenge, the potential of NGM-1 and NFM-1 as enantioselective adsorbents has been demonstrated using small-molecular-weight chiral probe molecules [ 24 , 25 ].…”