Supramolecular organic frameworks: engineering periodicity in water through host–guest chemistry

Abstract

The development of homogeneous, water-soluble periodic self-assembled structures comprise repeating units that produce porosity in two-dimensional (2D) or three-dimensional (3D) spaces has become a topic of growing interest in the field of supramolecular chemistry. Such novel self-assembled entities, known as supramolecular organic frameworks (SOFs), are the result of programmed host-guest interactions, which allows for the thermodynamically controlled generation of monolayer sheets or a diamondoid architecture with regular internal cavities or pores under mild conditions. This feature article aims at propagating the conceptually novel SOFs as a new entry into conventional supramolecular polymers. In the first section, we will describe the background of porous solid frameworks and supramolecular polymers. We then introduce the self-assembling behaviour of several multitopic flexible molecules, which is closely related to the design of periodic SOFs from rigid multitopic building blocks. This is followed by a brief discussion of cucurbit[8]uril (CB[8])-encapsulation-enhanced aromatic stacking in water. The three-component host-guest pattern based on this stacking motif has been utilized to drive the formation of most of the new SOFs. In the following two sections, we will highlight the main advances in the construction of 2D and 3D SOFs and the related functional aspects. Finally, we will offer our opinions on future directions for both structures and functions. We hope that this article will trigger the interest of researchers in the field of chemistry, physics, biology and materials science, which should help accelerate the applications of this new family of soft self-assembled organic frameworks.

Shape‐Controllable and Fluorescent Supramolecular Organic Frameworks Through Aqueous Host–Guest Complexation

“…[1,2] Inspired by these covalent framework materials in the solid state,s upramolecular scientists have prepared stable and functional noncovalent framework materials both in the solution and the crystalline state.T hese new materials have been referred to as supramolecular organic frameworks (SOFs). [3] SOFs are an ew type of porous framework materials in which the assembled structure is held together via noncovalent interactions,i ncluding hydrogen bonds, p-p stacking, and van der Waals interactions.A lthough some crystalline SOFs have been successfully used for gas adsorption, [4] Li, Zhao,and Feng reported the direct preparation and characterization of single-layer periodic honeycomb-shaped two-dimensional (2D) SOFs and ap eriodic adamantaneshaped three-dimensional (3D) SOF in water and the solid state through the self-assembly of various pyridinium derivatives with cucurbit [8]uril (CB [8]). [5][6][7] This previous work establishes that SOFs retain not only the highly efficient and dynamic reversible feature of noncovalent interactions but also the regularity or periodicity of the supramolecular architectures in solution, compared to MOFs,C OFs,a nd supramolecular polymers.…”

“…[5][6][7] This previous work establishes that SOFs retain not only the highly efficient and dynamic reversible feature of noncovalent interactions but also the regularity or periodicity of the supramolecular architectures in solution, compared to MOFs,C OFs,a nd supramolecular polymers. [3] On the other hand, the hierarchical preparation of 3D SOFs from hydrogen-bonded 2D networks with/without linkers have been proven as au seful strategy for constructing highly ordered porous framework materials. [8] However,tothe best of our knowledge,the report about hierarchical preparation of 3D SOFs from 2D networks formed through host-guest interactions is limited.…”

Towards the Prediction of Global Solution State Properties for Hydrogen Bonded, Self‐Associating Amphiphiles

“…This may also explain the low CMC calculated for 7 (96.35 mm). In an aqueous solution, the sodium ion exists as the hydrated complex [Na(H 2 O) 6 ] + .T his hydration process decreases the cations relative availablyt owards the formation of an ion-ionc omplex and therefore promotes urea-anion hydrogen bond formation in comparison to PyrH + (8 198.42 mm), TMA (9 209.98 mm) and TEA (10 103.13mm). These CMC values obtained for the sub series of compounds may also be influenced by the hydrophobicity of the counter cation.E vidence for this can also be seen in Figure 7, which shows acorrelationb etween increasing calculated counter cation LogP and decreasing CMC.…”

“…Enabling predictable control of these self-associative interactions at af undamentall evel not only influencest he fields associated with nanostructure formation, [3] specifically twocomponent self-associated systems, [4] but will also enablea step-change in the fields of supramolecular materials [5] and supramolecular organic frameworks (SOFs). [6] Within the extensive area of non-covalents elf-associated materiald esign, there is ag rowing interest in the focusedu se of intermolecular hydrogen bonds. Specific examples include those from Ikkala and co-workers who have used this class of non-covalent complex formation to drive the self-assembly of cobaltn anostructures for capsid production; [7] Yagai and coworkers who have used hydrogen bond formationw ithin the construction of novel molecular semi-conductors; [8] Steed and co-workersw ho have shown that hydrogen bonds can act as a substitute for covalent bonds in the production of novel supramolecular gels; [9] and Zhou and co-workers who have used hydrogen bonded amphiphile self-associationp rocesses to drive the construction of novel drug/gene delivery systems.…”

Metal–Organic Polyhedron Capped with Cucurbit[8]uril Delivers Doxorubicin to Cancer Cells

“…26,27,29,30 These CB[8] controlled systems have been used to advantage in the preparation of supramolecular polymeric systems for biological and materials applications, chemical sensing ensembles, molecular machines, non-covalent promotors of biological dimerization, and supramolecular catalysis. 27,31,32 Given their excellent biocompatibility, other recent efforts have sought to use CB[n]-type receptors to enhance drug solubility, for imaging applications, and as a drug reversal agent. 31,33 Pioneering work in this area was performed by Yang, Zink, and Stoddart based on mesoporous silica nanoparticles that are gated by host•guest recognition processes.…”