Enantioseparation on a chiral nanostructured surface: Effect of molecular shape

In this paper we use the Monte Carlo simulation method to study adsorption of chiral molecules on a solid surface with periodic distribution of active sites. Namely, equilibrium adsorption of a racemic mixture of enantiomers represented by homonuclear tetramers is modeled on a square lattice with a chiral pattern of active sites. We consider two possible chiral structures of the tetramers which differ only by chain geometry but have equal adsorption energies. The effect of the chain geometry on the effectiveness of separation is assessed by comparing the corresponding adsorption selectivities obtained from the simulations. We present results of model calculations in which the parameters do not refer to any particular experimental system. These results indicate that the model chiral surface can, in general, adsorb preferentially the complementary enantiomer, regardless of its chain conformation. Specifically, it was shown that changes in the tetramer geometry, from S-shaped to Γ-shaped, lead to marginal changes in the shape of both single component and mixed adsorption isotherms calculated for the enantioselective surface. In this context, the enantiomer separation on the surface proposed in this work was shown to be insensitive to molecular shape of the adsorbing species.