4.3.2. Hybrid Self-Assemblies Constructed from an Amphiphilic Calix[4]arene and Au Nanoparticles 7267 4.4. Photomodulated Fluorescence of Supramolecular Assemblies of Sulfonatocalixarenes and Tetraphenylethene 7267 4.5. Photodynamic Therapy System Fabricated from a Calixarene-Based Supramolecular Amphiphile 7268 4.6. Multi-Stimuli-Responsive Supramolecular Amphiphile as a Drug Delivery System 7269 4.7. Cholinesterase-Responsive Supramolecular Vesicles as Drug Delivery Carriers 7270 4.8. Supramolecular Amphiphiles Constructed from Calixarene Analogues 7271 4.8.1. Supramolecular Amphiphile Based on Calix[4]resorcinarene and a Cationic Surfactant for Controllable Self-Assembly 7271 4.8.2. Fabrication of Well-Defined Crystalline Azacalixarene Nanosheets Assisted by Se•••N Noncovalent Interactions 7272 5. Cucurbituril-Based Supramolecular Amphiphiles 7273 5.1. Supramolecular Vesicles Formed by Amphiphilc Cucurbit[6]uril and Multivalent Binding of Sugar-Decorated Vesicles to Lectin 7274 5.2. Supramolecular Photosensitizers with Enhanced Antibacterial Efficiency 7274 5.3. Supramolecular Approach To Fabricate Highly Emissive Smart Materials 7275 5.4. Cucurbit[8]uril-Based Ternary Supramolecular Amphiphiles 7276 5.4.1. Spontaneous Formation of Vesicles Triggered by Formation of a Charge-Transfer Complex in a Host 7276 5.4.2. Supramolecular Glycolipid Based on Host-Enhanced Charge-Transfer Interaction 7276 5.4.3. Supramolecular Peptide Amphiphile Vesicles through Host−Guest Complexation 7277 5.4.4. Biocompatible and Biodegradable Supramolecular Assemblies for Reduction-Triggered Release of Doxorubicin 7278 6. Pillar[n]arenes-Based Supramolecular Amphiphiles 7279 6.1. Pillar[n]arene-Based Enzyme-Responsive Supramolecular Amphiphiles 7279 6.2. Bola-Type Supramolecular Amphiphile Constructed from a Water-Soluble Pillar[5]arene and a Rod−Coil Molecule for Dual Fluorescent Sensing 7280 6.3. Cationic Water-Soluble Pillar[6]arene-Based Supramolecular Amphiphile 7281 6.4. Photoresponsive Self-Assembly Based on a Water-Soluble Pillar[6]arene and an Azobenzene-Containing Amphiphile in Water 7282 6.5. Four-Armed Supramolecular Amphiphile with Complexation-Induced Emission 7283 6.6. Supramolecular Amphiphiles as Multiwalled Carbon Nanotube Dispersants 7283 6.6.1. pH-Responsive Water-Soluble Pillar[6]arene-Based Supramolecular Amphiphile 7283 6.6.2. UV-Responsive Water-Soluble Pillar[6]arene-Based Supramolecular Amphiphile 7284 6.7. Supramolecular Amphiphiles Constructed on the Basis of Pillararene/Paraquat Recognition 7284 6.7.1. pH-Responsive Supramolecular Amphiphiles on the Basis of Molecular Recognition between Pillar[n]arenes (n = 6, 7, and 10) and Paraquat 7284 6.7.2. Supramolecular Hybrid Nanostructures Based on Pillar[6]arene Modified Gold Nanoparticles/Nanorods and Their Application in pH-and NIR-Triggered Controlled Release 7286 6.8. Water-Soluble Pillar[6]arene-Based Supramolecular Vesicles for Drug Delivery 7287 7. Supramolecular Amphiphiles Constructed by Other Macrocycle-Based Host−Guest Molecular Recognitions 7288 7.1.

Porous materials with high surface areas have drawn more and more attention in recent years because of their wide applications in physical adsorption and energy-efficient adsorptive separation processes. Most of the reported porous materials are macromolecular porous materials, such as zeolites, metal-organic frameworks (MOFs), or porous coordination polymers (PCPs), and porous organic polymers (POPs) or covalent organic frameworks (COFs), in which the building blocks are linked together by covalent or coordinative bonds. These materials are barely soluble and thus are not solution-processable. Furthermore, the relatively low chemical, moisture, and thermal stability of most MOFs and COFs cannot be neglected. On the other hand, molecular porous materials such as porous organic cages (POCs), which have been developed very recently, also show promising applications in adsorption and separation processes. They can be soluble in organic solvents, making them solution-processable materials. However, they are usually sensitive to acid/base and humid environments since most of them are based on dynamic covalent bonding. These macromolecular and molecular porous materials usually have two similar features: high Brunauer-Emmett-Teller (BET) surface areas and rigid pore structures, which are stable during adsorption and separation processes. In this Account, we describe a novel class of solid materials for adsorption and separation, nonporous adaptive crystals (NACs), which function at the supramolecular level. They are nonporous in the initial crystalline state, but the intrinsic or extrinsic porosity of the crystals along with a crystal structure transformation is induced by preferable guest molecules. Unlike solvent-induced crystal polymorphism phenomena of common organic crystals that occur at the solid-liquid phase, NACs capture vaporized guests at the solid-gas phase. Upon removal of guest molecules, the crystal structure transforms back to the original nonporous structure. Here we focus on the discussion of pillararene-based NACs for adsorption and separation and the crystal structure transformations from the initial nonporous crystalline state to new guest-loaded structures during the adsorption and separation processes. Single-crystal X-ray diffraction, powder X-ray diffraction, gas chromatography, and solution NMR spectroscopy are the main techniques to verify the adsorption and separation processes and the structural transformations. Compared with traditional porous materials, NACs of pillararenes have several advantages. First, their preparation is simple and cheap, and they can be synthesized on a large scale to meet practical demands. Second, pillararenes have better chemical, moisture, and thermal stability than crystalline MOFs, COFs, and POCs, which are usually constructed on the basis of reversible chemical bonds. Third, pillararenes are soluble in many common organic solvents, which means that they can be easily processed in solution. Fourth, their regeneration is simple and they can be reused many times...

The energy-efficient separation of alkylaromatic compounds is a major industrial sustainability challenge. The use of selectively porous extended frameworks, such as zeolites or metal–organic frameworks, is one solution to this problem. Here, we studied a flexible molecular material, perethylated pillar[n]arene crystals (n = 5, 6), which can be used to separate C8 alkylaromatic compounds. Pillar[6]arene is shown to separate para-xylene from its structural isomers, meta-xylene and ortho-xylene, with 90% specificity in the solid state. Selectivity is an intrinsic property of the pillar[6]arene host, with the flexible pillar[6]arene cavities adapting during adsorption thus enabling preferential adsorption of para-xylene in the solid state. The flexibility of pillar[6]arene as a solid sorbent is rationalized using molecular conformer searches and crystal structure prediction (CSP) combined with comprehensive characterization by X-ray diffraction and 13C solid-state NMR spectroscopy. The CSP study, which takes into account the structural variability of pillar[6]arene, breaks new ground in its own right and showcases the feasibility of applying CSP methods to understand and ultimately to predict the behavior of soft, adaptive molecular crystals.