Alkane Shape- and Size-Recognized Selective Vapor Sorption in "Channel-Like" Crystals Based on Thiacalixarene Assemblies

Clamparene: Synthesis, Structure, and Its Application in Spontaneous Formation of 3D Porous Crystals

Macrocyclic arenes have emerged as pivotal scaffolds in supramolecular chemistry. Despite their significant contributions to molecular recognition and diverse applications, challenges persist in the development of macrocyclic arene-based crystalline materials, particularly in achieving porosity and addressing limitations in adsorption efficiency resulting from the small cavity sizes of existing macrocyclic arenes. In this study, we present the design and synthesis of a novel macrocyclic arene, clamparene (CLP), featuring a rigid backbone, easy synthesis, and a sizable cavity. CLP self-assembles into one-dimensional sub-nanotubes that further organize into a three-dimensional porous framework in the solid state. The crystalline solid of CLP exhibits potential as a porous crystalline adsorbent for various benzene-based contaminants with rapid adsorption kinetics, large uptake amounts, and good recyclability.

Industrial Separation Challenges: How Does Supramolecular Chemistry Help?

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.

Facile separation of cyclic aliphatic and aromatic vapors using crystalline thiacalixarene assemblies with preorganized channels

Conventional distillation methods cannot separate compounds with similar boiling points, molecular sizes, and volumes, such as cyclohexane and benzene or methylcyclohexane and toluene, effectively. The corresponding cyclic aliphatic and aromatic hydrocarbons cannot be separated effectively using the same type of sorption material. We report that crystalline thiacalixarene assemblies featuring preorganized channel-like adsorption sites are capable of both separations.

Selective separation of branched alkane vapor by thiacalixarene supramolecular crystals having shape-recognition properties

Activated crystals of a supramolecular assembly of bromothiacalix[4]arene propyl ether with preorganized channel-like voids can selectively and effectively adsorb isooctane vapor from a vapor mixture of isooctane and n-heptane.