Nanoporous Nanorods Fabricated by Coordination Modulation and Oriented Attachment Growth
Nanoporous Nanorods Fabricated by Coordination Modulation and Oriented Attachment Growth
复制标题
DOI：
10.1002/anie.200901177
复制
发表时间：
2009-01-01
影响因子：
16.6
通讯作者：
Kitagawa, Susumu
中科院分区：
文献类型：
--
作者：
Tsuruoka, Takaaki;Furukawa, Shuhei;Kitagawa, Susumu
金属-有机杂化多孔材料是由有机连接体与金属离子组装而成的一种新型材料，称为多孔配位聚合物（PCPs）或金属-有机骨架（MOFs）。[1-6]这类材料最近被认为是一类有趣的晶体纳米多孔材料，用于气体吸附，分离和催化，因为它们的框架拓扑结构和孔径可以被设计用于选择性的客体容纳，并且孔表面的功能直接影响与客体分子的相互作用。通过功能化晶体界面将PCP晶体的尺寸微型化到纳米尺度[7-10]将提供进一步的机会，将新功能整合到材料中而不改变PCP晶体本身的特性特征，并将允许研究纳米晶体的多孔性质和界面结构之间的相关性。尽管纳米尺寸的PCP的优点，生长过程中最重要的是建立一个通用的方法来创建纳米尺寸的PCP仍然不清楚，因为没有合适的定义协议。[7，10-13]此外，了解骨架材料的晶体生长，有望确定自下而上自组装过程的基本要求。在这里，我们表明，一个简单而直接的方法，使用加帽试剂，干扰PCPs的框架延伸，可以应用于确定其晶体特征。我们描述了PCP纳米棒的四面体框架系统，通过选择性地调节框架中的配位相互作用来定义，这增强了立方纳米晶体的一维各向异性融合，表明定向附着机制。[14，15]此外，纳米棒的吸附性能和结晶度之间的相关性表明，配位调制法可以制备具有高孔隙率的高度结晶的纳米棒，与使用常规溶剂热法合成的块体晶体相比。相对较弱的配位键相互作用主导了构建稀疏的三层结构的分级自组装过程。具有纳米晶格常数的PCP的三维多孔框架，导致晶体的形成。这一特征将这类分子基材料与致密的无机材料（如金属[16]和半导体晶体[17]）以及传统的多孔材料（如沸石[18，19]和中孔二氧化硅）区分开来。[20当改变PCP的晶体特征（例如它们的尺寸、形态和结晶度）时，控制金属离子和有机连接体之间的相互作用（所谓的“配位平衡”）是重要的。虽然已经开发了几种方法来制造五氯苯酚纳米颗粒，例如反胶束[22]和微波辅助方法[23，24]，但由于难以控制骨架延伸的速率，因此很少讨论晶体生长机制。[25]我们的策略受到制造金属或半导体纳米颗粒的方法[26，27]以及Fischer及其同事所做的初步工作[7]的启发，通过简单地添加封端试剂来调节配位平衡（调节剂）具有与连接剂相同的化学官能度，以阻止金属离子和有机连接剂之间的配位相互作用，其产生调节骨架延伸和晶体生长速率的竞争性情形（方案1）。配位相互作用的选择性调制使我们能够控制所得的晶体形态，这…
Well-designed metal–organic hybrid porous materials—socalled porous coordination polymers (PCPs) or metal–organic frameworks (MOFs)—can be made from an assembly of organic linkers with metal ions.[1–6] This class of materials was recently recognized as an intriguing class of crystalline nanoporous materials for gas sorption, separation, and catalysis because their framework topologies and pore sizes can be designed for selective guest accommodation, and the functionality of the pore surfaces directly influences the interaction with guest molecules. Miniaturizing the size of PCP crystals to the nanometer scale [7–10] by functionalizing the crystal interfaces will provide further opportunities to integrate novel functions into the materials without changing the characteristic features of the PCP crystal itself, and will allow the correlation between the porous properties and interfacial structures of nanocrystals to be investigated. Despite the advantages of nanosized PCPs, growth processes that are most important in establishing a universal methodology for the creation of nanosized PCPs are still unclear because there is no suitable defining protocol.[7, 10–13] Understanding the crystal growth of framework materials, moreover, promises to determine the fundamental requirements of bottom-up selfassembly processes. Herein, we show that a simple but straightforward method using capping reagents that perturb the framework extension of PCPs can be applied to determine their crystal features. We describe the tetragonal framework system of PCP nanorods defined by selectively modulating the coordination interaction in the framework, which enhances the one-dimensional anisotropic fusion of the cubic nanocrystals, indicating an oriented attachment mechanism.[14, 15] Moreover, the correlation between the sorption properties and crystallinity of the nanorods shows that the coordination modulation method can produce highly crystalline nanorods with high porosity comparable to that of bulk crystals synthesized by using the conventional solvothermal method.The relatively weak interactions of the coordination bonds dominate the hierarchical self-assembly process involved in constructing the sparse three-dimensional porous frameworks of PCPs with nanometer lattice constants, leading to the formation of crystals. This feature distinguishes this class of molecular-based materials from dense inorganic materials, such as metal [16] and semiconductor crystals,[17] and from conventional porous materials such as zeolites [18, 19] and mesoporous silica.[20, 21] Controlling the interactions between metal ions and organic linkers, so-called “coordination equilibria”, is important when varying the crystal features of PCPs, such as their size, morphology, and crystallinity. Although several approaches have been developed to fabricate PCP nanoparticles, such as reversed micelles [22] and microwave-assisted methods,[23, 24] the crystal-growth mechanism has rarely been discussed because it is difficult to control the rate of framework extension.[25] Our strategy, inspired by the method to fabricate metal or semiconductor nanoparticles [26, 27] and by the preliminary work done by Fischer and coworkers,[7] is to modulate the coordination equilibria simply by adding capping reagents (modulators) with the same chemical functionality as the linkers, to impede the coordination interaction between the metal ions and the organic linkers, which generates a competitive situation that regulates the rate of framework extension and crystal growth (Scheme 1). The selective modulation of the coordination interactions allows us to control the resulting crystal morphology, which …