Recyclable Nanoporous Materials with Ordered Tunnels Self‐Assembled from α‐ and γ‐Cyclodextrins

Abstract

A straightforward method to create nanoporous materials via the self‐assembly of macrocyclic molecules (MCMs) is proposed and fulfilled by using cyclodextrins (CD) as building blocks. Due to molecular geometry, α‐CD forms a hexagonal nanoporous crystal, whereas γ‐CD forms a cuboid crystal. The resulting products are confirmed by FTIR, 1H NMR and solid‐state 13C NMR to be solely built up by CDs. Well‐defined and monodisperse nano‐tunnels are formed in nanoporous materials by the template‐free, face‐to‐face self‐assembly of CDs, with diameters around 0.8 or 0.5 nm equal to the diameter of the CD cavities. Moreover, the nanoporous structure of the CD is reversible controlled simply by switching temperature in DMF, indicating that the nanoporous CDs could be recyclable used and recovered. These characteristic properties and behaviors of the nanoporous CDs made them to be an ideal green material for absorption, separation as well as CD recovery.

Reaction-Spun Transparent Silica Aerogel Fibers

“…The results showed that too little water could not assist TEOS in hydrolyzing enough to form the CS colloidal particles, while too much water might result in the gelated CS network. 36 For the chemical structure, the 29 Si NMR spectrum of CS 1.2−0.01 in Figure 1e 37 The sharp and multiple peaks suggest that CS 1.2−0.01 was a mixture of soluble oligomers. The integral areas of the Q 1 /Q 2 /Q 3 were ca.…”

“…Furthermore, to show the effect of H 2 O/TEOS during CS preparation, dynamic light scattering (Figure 1d), 29 Si NMR (Figure 1e), and Tyndall observation (Insets in Figure 1d) were applied for the CS 1.2−0.01 and CS 2.8−0.01 spinning solutions, respectively. During hydrolysis, an ethoxy was replaced with a −OH in water to form a silanol group, and then silanol groups reacted with each other to form siloxane bridges.…”

“…1:2:1, indicating that the structure of CS 1.2−0.01 was a possible tetramer with a hexatomic ring (Figure S1). The 29 Si NMR spectrum of CS 2.8−0.01 showed broad peaks located at −90, − 100, and −110 ppm, corresponding to Q 2 , Q 3 , and Q 4 (Si tetrahedra with four Si−O−Si bond), and the integral areas of peak indicated that the percentages of Q 2 , Q 3 , and Q 4 were 12, 61 and 27%, respectively, suggesting a highly cross-linked network. The Tyndall effect was further examined for the two solutions, and only the CS 2.8−0.01 solution showed a clear light scattering, further indicating that CS 1.2−0.01 was soluble small molecules while CS 2.8−0.01 was colloidal particles.…”

Advances in Cyclodextrin Polymers and Their Applications in Biomedicine

“…纯 CD 都具有高 度结晶结构, CD 分子之间相互堆叠, 空腔通常被相邻 CD 阻隔, 因此 CD 的固态包结能力较弱, 客体分子难以 扩散至 CD 晶体内部. 将 CD 充分溶解在二甲基甲酰胺 (DMF)中, 再通过加温可实现 α-和 γ-CD 的有序排列和 管道结晶的形成, 使 CD 空腔面与面堆叠形成单分散亚 纳米孔道结构, 将 CD 分子的空腔完全展露出来 [9] , 虽 然其固-液吸附能力有一定的提高, 但与理论计算值仍 然相差较远, 主要原因在于表层 CD 的空腔包覆客体分 子之后, 缺乏往内运动的驱动力. 通过喷雾干燥法可抑 制 CD 结晶并获得无定形 CD 颗粒, 提高了固态下 CD 的吸附能力 [10,11] , 但 CD 的无定形结构极不稳定, 在湿 度或温度较高情况下都能自发结晶.…”

Ultralight hybrid silica aerogels derived from supramolecular hydrogels self-assembled from insoluble nano building blocks

“…For instance, hydrogels are reversible and stimuli-responsive, but the stimuli-responsiveness in aerogels are rare because the movements of molecules are restricted in the solid state. 10,11 On the other hand, supramolecular hydrogels are normally formed by soluble precursors, [38][39][40][41] which are soluble in the molecular level when they form the hydrogel networks. Due to the weak connection of supramolecular hydrogels, their corresponding aerogels cannot be obtained because there are no preformed network to support their volumes and structures.…”