Topochemical Synthesis of Single-Crystalline Hydrogen-Bonded Cross-Linked Organic Frameworks and Their Guest-Induced Elastic Expansion
Topochemical Synthesis of Single-Crystalline Hydrogen-Bonded Cross-Linked Organic Frameworks and Their Guest-Induced Elastic Expansion
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DOI：
10.1021/jacs.9b05232
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发表时间：
2019-07-10
影响因子：
15
通讯作者：
Ke, Chenfeng
中科院分区：
文献类型：
--
作者：
Jiang, Xuanfeng;Cui, Xunzhe;Ke, Chenfeng
共价连接的单晶多孔有机材料是结构性能分析的理想材料；然而，将有机实体周期性地聚合成高维网络是具有挑战性的。在这里，我们报道了一系列拓扑不同的单晶氢键交联有机框架（H(C)OFs），具有可见的客体诱导弹性膨胀，它们将高结构秩序和高灵活性相互整合到一个框架中。这些H(C)OFs是由不同链长的烷基二硫醇分子晶体光交联合成的。通过单晶x射线分析和H(C)OFs及其相应的单晶类似物的实验研究，揭示了它们的详细结构信息。在客体吸附后，由三维自纠缠聚合物网络组成的hcof -2晶体发生各向异性膨胀，其大小是原始尺寸的两倍以上，而二维双层HCOF-3晶体呈现出可见的分层吸附带，并沿着其二维层的平面形成分层片。根据其破纪录的水碘吸附能力计算，HCOF网络的动态扩展产生了比永久空隙大473%以上的访客诱导孔隙。温度门控DMSO吸附研究表明，H(C)OFs中交联剂的柔性性质为多种构象共存提供了正熵，从而允许框架的弹性膨胀和收缩。
Covalently linked single-crystalline porous organic materials are highly desired for structure-property analysis; however, periodically polymerizing organic entities into high dimensional networks is challenging. Here, we report a series of topologically divergent single-crystalline hydrogen-bonded cross-linked organic frameworks (H(C)OFs) with visible guest-induced elastic expansions, which mutually integrate high structural order and high flexibility into one framework. These H(C)OFs are synthesized by photo-cross-linking molecular crystals with alkyldithiols of different chain lengths. Their detailed structural information was revealed by single-crystal X-ray analysis and experimental investigations of H(C)OFs and their corresponding single-crystalline analogues. Upon guest adsorption, HOOF-2 crystals composed of a 3D self-entangled polymer network undergo anisotropic expansion to more than twice their original size, while the 2D-bilayer HCOF-3 crystals exhibit visible, layered sorption bands and form delaminated sheets along the plane of its 2D layers. The dynamic expansion of HCOF networks creates guest-induced porosity with over 473% greater volume than their permanent voids, as calculated from their record-breaking aqueous iodine adsorption capacities. Temperature-gated DMSO sorption investigations illustrated that the flexible nature of cross-linkers in H(C)OFs provides positive entropy from the coexistence of multiple conformations to allow for elastic expansion and contraction of the frameworks.