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.