With the increasing demand on chemicals geared by the rapid development of industries, such as the petrochemical and pharmaceutical industries, innovative materials and technologies are essential to improve the efficiency, safety, and the associated energy penalty of these processes. Disubstituted benzene isomers such as xylenes, dichlorobenzenes, dibromobenzenes, chlorotoluenes and others are the starting materials for many polymers, plastics, fibers, solvents and fuel. The separation of benzene isomers has been one of the most challenging separation due to their identical molecular weights, similar structures, and close boiling points. Distillation, the traditional separation method for benzene derivatives in industry, is highly energy-intensive due to the huge numbers of theoretical plates required for these processes. It is estimated that 30% of the overall energy production is utilized in industrial separation world-wide.
Adsorption by porous materials, such as zeolites, metal organic frameworks (MOFs), covalent organic frameworks (COFs), porous organic cages (POCs) and porous coordination polymers (PCPs) has proved to be quite efficient for the separation of disubstituted benzene isomers. However, in all the cases of solid-vapor adsorption separation, the vapor production and desorption processes need high temperature and high pressure which means steep energy requirements. Intrinsically porous materials (IPMs) are a promising alternative as sorbents for energy intensive separations as they are made from discrete organic molecules with accessible “built-in” pores or windows. These stable systems are easily prepared and scaled-up in addition to being solution processable, which makes them very attractive for industrial translation.