Tian-You Zhou

One-Step Construction of Two Different Kinds of Pores in a 2D Covalent Organic Framework

Covalent organic frameworks (COFs) are crystalline porous materials bearing microporous or mesoporous pores. The type and size of pores play crucial roles in regulating the properties of COFs. In this work, a novel COF, which bears two different kinds of ordered pores with controllable sizes: one within microporous range (7.1 Å) and the other in mesoporous range (26.9 Å), has been constructed via one-step synthesis. The structure of the dual-pore COF was confirmed by PXRD investigation, nitrogen adsorption-desorption study, and theoretical calculations.

Construction of Covalent Organic Frameworks Bearing Three Different Kinds of Pores through the Heterostructural Mixed Linker Strategy

It is very important to create novel topologies and improve structural complexity for covalent organic frameworks (COFs) that might lead to unprecedented properties and applications. Despite the progress achieved over the past decade, the structural diversity and complexity of COFs are quite limited. In this Communication, we report the construction of COFs bearing three different kinds of pores through the heterostructural mixed linker strategy involving the condensation of a D2h-symmetric tetraamine and two C2-symmetric dialdehydes of different lengths. The complicated structures of the triple-pore COFs have been confirmed by powder X-ray diffraction and pore size distribution analyses.

Three-dimensional periodic supramolecular organic framework ion sponge in water and microcrystals

Self-assembly has emerged as a powerful approach to generating complex supramolecular architectures. Despite there being many crystalline frameworks reported in the solid state, the construction of highly soluble periodic supramolecular networks in a three-dimensional space is still a challenge. Here we demonstrate that the encapsulation motif, which involves the dimerization of two aromatic units within cucurbit[8]uril, can be used to direct the co-assembly of a tetratopic molecular block and cucurbit[8]uril into a periodic three-dimensional supramolecular organic framework in water. The periodicity of the supramolecular organic framework is supported by solution-phase small-angle X-ray-scattering and diffraction experiments. Upon evaporating the solvent, the periodicity of the framework is maintained in porous microcrystals. As a supramolecular ‘ion sponge’, the framework can absorb different kinds of anionic guests, including drugs, in both water and microcrystals, and drugs absorbed in microcrystals can be released to water with selectivity.

A two-dimensional single-layer supramolecular organic framework that is driven by viologen radical cation dimerization and further promoted by cucurbit[8]uril

A two-dimensional supramolecular organic framework has been constructed in water from a rigid water-soluble triangular building block which is driven by the dimerization of three appended viologen radical cation units. Cucurbit[8]uril (CB[8]) further stabilizes the single-layer network by encapsulating the stacking viologen radical cation dimers. The new supramolecular networks have been characterized with UV-vis absorption, electron paramagnetic resonance, dynamic light scattering, solution and solid phase small angle X-ray diffraction, and AFM experiments. The aggregation behaviour is in sharp contrast to that of a triangular control compound, which only forms a discrete dimer or a 2 : 3 encapsulation complex in the absence or presence of CB[8].

Self‐Assembly of Three‐Dimensional Supramolecular Polymers through Cooperative Tetrathiafulvalene Radical Cation Dimerization

The self-assembly of a new type of three-dimensional (3D) supramolecular polymers from tetrahedral monomers in both organic and aqueous media is described. We have designed and synthesized two tetraphenylmethane derivatives T1 and T2, both of which bear four tetrathiafulvalene (TTF) units. When the TTF units were oxidized to the radical cation TTF(.+) , their pre-organized tetrahedral arrangement remarkably enhanced their intermolecular dimerization, leading to the formation of new 3D spherical supramolecular polymers. The structure of the supramolecular polymers has been inferred on the basis of UV/Vis absorption, electron paramagnetic resonance, cyclic voltammetry, and dynamic light scattering (DLS) analysis, as well as by comparing these properties with those of the self-assembled structures of mono-, di-, and tritopic control compounds. DLS experiments revealed that the spherical supramolecular polymers had hydrodynamic diameters of 68 nm for T1 (75 μM) in acetonitrile and 105 nm for T2 (75 μM) in water/acetonitrile (1:1). The 3D spherical structures of the supramolecular polymers formed in different solvents were also supported by SEM and AFM experiments.

Highly thermally stable hydrogels derived from monolayered two-dimensional supramolecular polymers

It has been predicted that the properties of materials are dramatically influenced if their structures are confined to two-dimensional (2D) space. A representative example is graphene. However, for synthetic 2D materials, such influences have rarely been demonstrated. In this work, a rare example of how a 2D monolayer structure can impact the properties of bulk materials has been demonstrated by the construction of 2D supramolecular polymers (SPs) and their utilization in the fabrication of hydrogels. Maintaining the intrinsic 2D structures, the as-prepared hydrogels exhibited exceptional thermal stabilities (>180 °C), as revealed by an inversion test and a variable-temperature rheological study. The microstructures and morphologies of the 2D SPs have been extensively characterized by NMR spectroscopy, dynamic light scattering, small-angel X-ray scattering, transmission electron microscopy and atomic force microscopy. Furthermore, molecular dynamic simulations were also performed to shed light on the formation mechanism of the hydrogels.

The construction of single-layer two-dimensional supramolecular organic frameworks in water through the self-assembly of rigid vertexes and flexible edges

Single-layer two-dimensional supramolecular organic frameworks have been constructed in water through three-component self-assembly of rigid cross-shaped vertexes, flexible oligoethylene glycol edges, and cucurbit[8]uril (CB[8]) hosts, driven by CB[8]-encapsulation-enhanced donor–acceptor interaction between the viologen unit and 2,6-dihydroxynaphthalene segment which were peripherally incorporated into the vertex and edge, respectively.

Redox-responsive reverse vesicles self-assembled by pseudo[2]rotaxanes for tunable dye release.

Reverse vesicles exhibiting functions similar to those of normal vesicles have been constructed through the self-assembly of TTF/CBPQT(4+)-based pseudo[2]rotaxanes in a nonpolar solvent. The ends of the threads of the pseudo[2]rotaxanes are attached with a Fréchet-type G-3 dendron and a hydrogen-bonded arylamide foldamer. These vesicles exhibit a response to redox. By exploiting the dynamic feature-spontaneously slow disassociation of the pseudorotaxanes-the sustained release of dyes embedded in the reverse vesicles has been demonstrated, which can be further tuned by changing the solvent polarity.

Encapsulation Enhanced Dimerization of a Series of 4-Aryl-N- Methylpyridinium Derivatives in Water: New Building Blocks for Self- Assembly in Aqueous Media

The construction of supramolecular systems in aqueous media is still a great challenge owing to the limited sources of building blocks. In this study, a series of 4-aryl-N-methylpyridinium derivatives have been synthesized. They formed very stable host-guest (1:2) complexes with CB[8] in water (binding constants up to 10(14)  M(-2)) with the two guest molecules arranged in a head-to-tail manner and the complexes showed high thermostability, which was revealed by (1) H NMR and UV/Vis spectroscopic studies, ITC, and crystallographic analysis.

A Triptycene-Based Microporous Organic Polymer Bearing Tridentate Ligands and Its Application in Suzuki-Miyaura Cross-Coupling Reaction

A triptycene-based microporous organic polymer (MOP) in which 2,6-bis(benzimidazol-2-yl)pyridine (bbp) is incorporated as linkage and coordination site is designed and synthesized. Pd(II) ions are further immobilized in this MOP through the coordination interactions between Pd(II) ion and nitrogen atoms of bbp. The resulting material shows high stability and exhibits excellent heterogeneously catalytic activity for the Suzuki-Miyaura cross-coupling reaction. Its high efficiency can be maintained after being reused for a number of cycles.