Conformation-induced separation of 3-chloropropene from 1-chloropropane through nanoporous monolayer graphenes.

ABSTRACT

Achieving ultrahigh selectivity for separating paraffin/olefin mixtures with physical and chemical similarity, especially for halohydrocarbons, is a long-standing challenge in high-purity polymer production. We explored three H-saturated nanoporous graphene (NG) membranes with appropriate pore geometries that can achieve the complete exclusion of 1-chloropropane (C3H7Cl) from C3H5Cl during molecular dynamics simulations. Inferred from thermodynamics calculations, C3H5Cl has a lower energy barrier of penetration than C3H7Cl and the NG membranes show preferential adsorption to C3H5Cl, which facilitate the penetration of C3H5Cl through the pores. The conformational energy analysis of the two molecules shows that C3H5Cl has a lower energy penalty to twist to the molecular conformation that nanopores preferred than C3H7Cl, which mainly determines the ultrahigh selectivity for C3H5Cl. We anticipate that the conformation-induced mechanism outlined here can provide a reference to separate paraffin/olefin mixtures with distinctly different conformational energy profiles.