Porous coordination-polymer crystals with gated channels specific for supercritical gases
Porous coordination-polymer crystals with gated channels specific for supercritical gases
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DOI：
10.1002/anie.200390130
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发表时间：
2003-01-01
影响因子：
16.6
通讯作者：
Kitagawa, S
中科院分区：
文献类型：
--
作者：
Kitaura, R;Seki, K;Kitagawa, S
新型纳米多孔材料如配位聚合物和无机沸石的合成和表征是近年来研究的热点，因为它们在气体存储、分子筛、尺寸或形状选择性催化和离子交换等方面具有广泛的应用前景。[1±7]为了成功执行这些功能，多孔框架的坚固性和稳定性至关重要。相比之下，响应于客体分子的柔性主体框架，例如，蛋白质与其底物之间的诱导配合识别，对客体包含具有高选择性。配位聚合物，尽管它们的结晶形式，适合于产生柔性和动态多孔框架，所谓的第三代化合物，[8]因为各种各样的结构和拓扑结构不仅基于配位键，而且基于氢键和/或π±π堆叠，其比沸石中的SiO2和Al 2 O3键弱。[9±13]因此，我们专注于制备两种新型的柔性和动态纳米多孔框架，这些框架由具有交叉和相互渗透的配位聚合物创建，并在高压和环境温度下研究气体吸附性能（CO2，CH 4，O2和N2）。我们的策略，功能性配位聚合物，响应客体分子是组装刚性图案与位移的自由度，以提供两种类型的集成框架（图1）：框架A与相互交叉的二维（2D）的图案，和框架B与相互渗透的三维（3D）的图案。结构基元的刚性和位移的自由度都可以引起整个框架的柔性，从而改善多孔性能。以硝酸铜、2，5-二羟基苯甲酸（Hdhbc）和4，4 ′-联吡啶（4，4 ′-bpy）为原料，合成了一种A型配位聚合物[Cu（dhbc）2（4，4 ′-bpy）]·H2O（1a）。铜离子通过4，4 '-bpy连接以产生直链，并通过dhbc连接以产生2D片基序（分别为图2a和图B）。图案有由dhbc苯平面以直立方式构造的联锁脊和凹。最近邻的dhbc配体的平面之间的距离为3.443 ε，表明存在π±π堆积相互作用，并且基序相互交叉以产生沿着a轴的具有3.6 π 4横截面的1D通道。2 ä（图2c），其中每个铜离子包含一个水分子。以Cu Ⅱ、苯-1，4-二甲酸酯（bdc）和4，4 ′-bpy为原料合成了B型配位聚合物2。由CuII和bdc组成的二维网格型片层通过4，4 '-bpy连接以产生类似于普鲁士蓝结构的3D丛林健身房框架。两个独立的3D结构相互渗透，形成一个具有圆柱形通道的3D框架，其沿着c轴的尺寸约为3.4 <$3.4 ä（图3）。[14]1a的热重分析显示，随着温度升高至1208 ℃，结晶水分子释放，得到无水客体1b。在1208 ℃和1708 ℃之间没有观察到进一步的重量损失，即无客体相是稳定的。由于1b的X射线粉末衍射（XRPD）图（图4）显示出与1a类似的尖锐衍射峰，因此即使没有水分子，多孔骨架也基本上得以保持。两个XRH）图的详细比较揭示，对于峰（010）和（100）仅观察到小的位移，其分别归因于ac和bc平面。因此，2D层图案在…
Considerable effort has been devoted to the synthesis and characterization of new crystalline nanosized porous materials, such as coordination polymers and inorganic zeolites, because of their versatile applicability to gas storage, molecular sieves, size-or shape-selective catalysis, and ion exchange.[1±7] For successful performance of these functions, robustness and stability of the porous frameworks are essential. In contrast, flexible host frameworks that respond to guest molecules, for example, induced-fit recognition between a protein and its substrate, have high selectivity for guest inclusion. Coordination polymers, in spite of their crystalline form, are suitable for creating flexible and dynamic porous frameworks, so-called third-generation compounds,[8] because the wide variety of architectures and topologies are based not only on coordinative bonds, but also on hydrogen bonds and/or π±π stacking, which are weaker than the SiÀO and AlÀO bonds in zeolites.[9±13] Hence, we focused on the preparation of two new types of flexible and dynamic nanoporous frameworks created by coordination polymers with interdigitation and interpenetration, and examined the gas-adsorption properties (CO2, CH4, O2, and N2) at high pressure and ambient temperature. Our strategy for functional coordination polymers that respond to guest molecules is to assemble rigid motifs with a degree of freedom in displacement to provide two types of integrated frameworks (Figure 1): framework A with mutually interdigitated two-dimensional (2D) motifs, and framework B with mutually interpenetrated three-dimensional (3D) motifs. Both the rigidity of a structural motif and a degree of freedom in displacement could give rise to flexibility of the whole framework and thus improve porous properties. A coordination polymer of typeA, namely,[Cu (dhbc) 2 (4, 4’-bpy)]¥ H2O (1a), was prepared from CuII nitrate, 2, 5-dihydroxybenzoic acid (Hdhbc), and 4, 4’-bipyridine (4, 4’-bpy). The copper ions are connected by 4, 4’-bpy to produce straight chains, and linked by dhbc to give a 2D sheet motif (Figure 2a and b, respectively). The motif has interlocking ridges and hollows constructed by the dhbc benzene planes in an upright fashion. The distance of 3.443 ä between the planes of the nearest-neighbor dhbc ligands indicates the presence of π±π stacking interactions, and the motifs are mutually interdigitated to create 1D channels along the a axis with a cross section of 3.6 î4. 2 ä (Figure 2c), in which one water molecule is included per copper ion. The typeB coordination polymer 2 was obtained by using CuII, benzene-1, 4-dicarboxylate (bdc), and 4, 4’-bpy. Two-dimensional grid-type sheets composed of CuII and bdc are linked by 4, 4’-bpy to produce a 3D jungle-gym-like framework, similar to the structure of Prussian Blue. Two independent 3D structures interpenetrate each other to form a 3D framework with cylindrical channels with approximate dimensions of 3.4 î 3.4 ä along the c axis (Figure 3).[14] Thermogravimetric analysis of 1a shows the release of water molecules of crystallization with increasing temperature up to 1208C to give guest-free anhydrous 1b. No further weight loss was observed between 1208C and 1708C, that is, the guest-free phase is stable. Since the X-ray powder diffraction (XRPD) pattern of 1b (Figure 4) shows sharp diffraction peaks similar to those of 1a, the porous framework is largely maintained, even without water molecules. Detailed comparison of the two XRPD patterns reveals that only small shifts were observed for the peaks (010) and (100), which are attributed to the ac and bc planes, respectively. Therefore, the 2D layer motif is retained during …