Kinetics and equilibrium of multicomponent adsorption on chiraly templated surfaces

Abstract

In this contribution we propose a simple model of adsorption of a binary (racemic) mixture on a chiraly templated surface. As an example, the adsorption of a liquid mixture of enantiomers on a chiral stationary phase (CSP) is considered. In particular, we study the effect of the lateral interactions in the adsorbed phase on the kinetic and equilibrium isotherms of the enantiomers. Additionally, we investigate the influence of the composition of the surface on the performance of the CSP in the presence of the lateral interactions. To that end, the adsorption of the mixture is modeled by using Monte Carlo simulations as well as by applying an analytical approach involving rate equations coupled with the Mean Field Approximation (MFA). The predictions of the theory are found to be in good agreement with the results of the simulations.

Extended Surface Chirality for Enantiospecific Adsorption

“…Specifically, when the coverage increases, the surface loses it preference for adsorption of S enantiomers because the clusters of active sites matching the footprint of enantiomer S (clusters with two active sites) are partially occupied by the opposite enantiomer. This general tendency involving blockage of chiral centres has also been observed for adsorption of racemic mixtures on other chiral adsorbents, such as CSPs47, 62 and chirally templated surfaces 46. A combination of the two effects described above results in a largely diversified interaction pattern of the enantiomers with the chiral surface.…”

“…This general tendency involving blockage of chiral centres has also been observed for adsorption of racemic mixtures on other chiral adsorbents, such as CSPs [47,62] and chirally templated surfaces. [46] A combination of the two effects described above results in a largely diversified interaction pattern of the enantiomers with the chiral surface. This makes theoretical description of the selectivity at high coverages quite difficult.…”

“…[22] With regard to chirally templated surfaces, the adsorption of chiral molecules has been modelled theoretically by using statistical mechanics and the MC method. [44][45][46][47] A direct observation from the studies cited above is that the enantioselectivity of chiral surfaces originates mainly from specific intermolecular interactions between a well-defined chiral centre and the complementary enantiomer. In this case, a one-to-one correspondence is usually preserved such that the local chirality of the surface is the deciding factor in the enantiodiscrimination process.…”

Spontaneous segregation on a hybrid chiral surface

“…This is because of the increasing demand for new methods of enantioseparation and enantioselective synthesis carried out at macroscale. In the first case, the simulations embrace adsorption of enantiomers on chiral stationary phases (CSPs) used in liquid chromatography41–43 and enantioseparations performed using homochiral porous materials 44. In the latter case, chirally templated surfaces created usually by adsorption of chiral organic molecules on metallic crystals45, 46 are of the main interest.…”

Tuning Selectivity in Adsorption on Composite Chiral Surfaces

“…In this case, a one-to-one correspondence is usually preserved such that, in principle, a larger number of chiral ligands means higher selectivity for the CSP. [5][6][7] A different mechanism of enantiodiscrimination can occur for solid surfaces templated with chiral organic molecules, particularly metallic crystal faces templated with modifiers such as cinchona alkaloid 1 or 2-butanol. 8,9 In those cases, a suitable spatial distribution of the template molecules leads to the formation of chiral pockets promoting enantioselective adsorption or reactions.…”