Nonporous Adaptive Calix[4]pyrrole Crystals for Polar Compound Separations

Abstract

The use of molecular crystalline materials for the separation and purification of chemical raw materials, particularly polar compounds with similar physical and chemical properties, represents an ongoing challenge. This is particularly true for volatile feedstocks that form binary azeotropes. Here we report a new cavity-extended version of calix[4]pyrrole (C4P) that readily forms nonporous adaptive crystals (NACs). These C4P-based NACs allow pyridine to be separated from toluene/pyridine mixtures with nearly 100% purity, as well as the removal of 1,4-dioxane from 1,4-dioxane/water mixtures with high adsorption capacity. Removal of the polar guest (pyridine or 1,4-dioxane) from the guest-loaded NACs by heating under vacuum produces the guest-free crystalline form. In the case of both guests, the C4P material could be reused as demonstrated through 10 uptake and release cycles without apparent performance loss.

Adsorptive separation of cyclohexanol and cyclohexanone by nonporous adaptive crystals of RhombicArene

“…Notably, it takes less than 30 min for the CHON adsorption to reach saturation, which is significantly faster compared to most NAC materials reported to date. 6,15 Powder X-ray diffraction analysis (PXRD, Fig. 3b and S7 † ) revealed the crystallinity of the activated 1, whose PXRD patterns matched with the simulated results based on the crystal structure of 1, suggesting comparable molecular packing modes.…”

“…Recently, macrocycle-based nonporous adaptive crystals (NACs) have emerged as efficient and selective adsorbents for mixed organic vapors with similar boiling points. 6 The high selectivity of the NAC strategy offers potential for economical and environmentally friendly separation of organic vapors, and stems from the deliberately designed macrocycles whose adaptive skeletons can provide noncovalent interactions to recognize certain guest molecules. Specifically, successful examples of NAC materials often employ electron-rich arene-based macrocycles, functioning as sources for C–H⋯π interactions.…”

Guest-induced amorphous-to-crystalline transformation enables sorting of haloalkane isomers with near-perfect selectivity

“…Supramolecular macrocycle-based crystalline molecular adsorbents have attracted much attention from chemists over the past few years and acquired inestimable benefits from the development of novel synthetic macrocyclic host compounds with distinctive topologies and intriguing properties (32)(33)(34)(35)(36). With the increased understanding of host-guest chemistry, structure-function relationship, noncovalent interactions, and dynamic molecular assembly, the creative design of macrocycle-based supramolecular materials with growing complexity, functionality, and applicability could be implemented with great ease.…”

Reimplementing Guest Shape Sorting of Nonporous Adaptive Crystals via Substituent‐Size‐Dependent Solid‐Vapor Postsynthetic Modification

“…We have recently proposed an original concept, nonporous adaptive crystals (NACs), which are a new kind of solid adsorptive materials [25–46] . Induced by guest vapors, these nonporous crystalline materials undergo a structural transformation to accommodate guest molecules.…”