Industrial Separation Challenges: How Does Supramolecular Chemistry Help?

Abstract

The chemical industry and the chemical processes underscoring it are under intense scrutiny as the demands for the transition to more sustainable and environmentally friendly practices are increasing. Traditional industrial separation systems, such as thermally driven distillation for hydrocarbon purification, are energy intensive. The development of more energy efficient separation technologies is thus emerging as a critical need, as is the creation of new materials that may permit a transition away from classic distillation-based separations. In this Perspective, we focus on porous organic cages and macrocycles that can adsorb guest molecules selectively through various host−guest interactions and permit molecular sieving behavior at the molecular level. Specifically, we summarize the recent advances where receptor-based adsorbent materials have been shown to be effective for industrially relevant hydrocarbon separations, highlighting the underlying host−guest interactions that impart selectivity and permit the observed separations. This approach to sustainable separations is currently in its infancy. Nevertheless, several receptor-based adsorbent materials with extrinsic/intrinsic voids or special functional groups have been reported in recent years that can selectively capture various targeted guest molecules. We believe that the understanding of the interactions that drive selectivity at a molecular level accruing from these initial systems will permit an ever-more-effective "bottom-up" design of tailored molecular sieves that, in due course, will allow adsorbent material-based approaches to separations to transition from the laboratory into an industrial setting.

Exclusive ion recognition using host–guest sandwich complexes

“…The extraction of undesired solutes, such as water or background electrolyte, presents a major challenge in host–guest complexation-based separation methods. 1 This results in increased processing costs and reduced efficiency. Numerous supramolecular strategies based on host–guest complexation have been developed to address these limitations, which utilize cyclic polymeric hosts with size-specific cavities to selectively bind desired ions based on their fit within the cavity.…”

“…This recognition led to further research and diversification of applications for these supramolecular systems, which have since been employed in a myriad of applications, ranging from separation sciences to the synthesis of molecular machines. 1,7,8 Recent trends in the field have shown a growing interest in leveraging supramolecular-based ligands for the selective separation of critical materials, underscoring their potential in addressing contemporary material challenges. 9,10 Ion-polyether host-guest interactions occur non-covalently through ion-dipole supramolecular interactions, where the selectivity of ion binding correlates with host cavity size, composition, and ion radius (r).…”

Highly selective separation of toluene/methylcyclohexane based on pagoda[5]arene nonporous adaptive crystals

“…17–19 These adsorbents have shown exceptional capabilities in discriminating structurally similar guests with close boiling points. 20–22 Recent studies have introduced various supramolecular macrocycles with well-defined cavity sizes, enabling precise molecular separations. 23 Notably, Chen and colleagues have developed a novel macrocyclic container called pagoda[5]arene ( P5 ), 24 which has expanded the toolbox of macrocyclic chemistry.…”

Controlling the crystal packing and morphology of metal–organic macrocycles through side-chain modification

“…[1][2][3][4][5] As molecules, macrocycles offer processability along with the ability to tune chemical structure with atomic precision. As materials, they possess multifunctional pore channels that can be used to mimic biological water channels, 6 selectively transport molecules, 7,8 conduct ions, [9][10][11][12] and host chemical reactions. 13,14 In addition, because the supramolecular architectures are held together by weak noncovalent interactions, these self-assembled nanotubes provide dynamic and stimuli-responsive properties.…”