«Kenji Hirai 2013 Preface The study in this thesis has been carried out under the direction of Professor Susumu Kitagawa at during April 2007 - March ...»
Studies on Macroscale Structuralization
of Porous Coordination Polymers
The study in this thesis has been carried out under the direction of Professor
Susumu Kitagawa at during April 2007 - March 2013 at Department of Synthetic
Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University.
The author is greatly indebted to Professor Susumu Kitagawa for his significant
guidance, valuable suggestions and continuous encouragement. The author wishes to express his hurtful gratitude to Professor Masaaki Ohba (Kyushu University), Dr.
Ho-Chol Chang (Hokkaido University), Dr. Takashi Uemura, Dr. Satoshi Horike, Dr.
Masakazu Higuchi, Professor Takafumi Ueno (Tokyo Institute of Technology), Dr.
Ryotaro Matsuda and Dr. Hiroshi Kajiro (Nippon Steel & Sumitomo Metal Corporation), for their helpful suggestions and hearty encouragements.
The author is grateful to Dr. Shuhei Furukawa for his continuous guidance and helpful discussions. The author expresses his gratitude to Dr. Osami Sakata (National Institute for Materials Science) for his collaborative work on the synchrotron X-ray diffraction experiments and valuable discussions. The author is grateful to Professor Christof Wöll (The Karlsruhe Institute of Technology), Dr. Osama Shekah (King Abdullah University of Science and Technology), Dr. Hui Wang and Professor Roland Fischer (Ruhr-Universität Bochum) for their collaborative work and kind hospitality during my short stay in Germany.
The author expresses his extreme gratitude to his colleges, Dr. Yohei Takashima (University of Glasgow), Dr. Ingmar Piglosiewicz (Wacker Chemie AG), Dr. Mio Kondo (Institute for Molecular Science), Dr. Takaaki Tsuruoka (Konan University), Dr.
Hiromitsu Uehara (Hokkaido University), Dr. Stéphane Diring, Dr. Julien Reboul, Mr.
Masashi Nakahama, Dr. Nicolas Louvain (Blaise Pascal University), Dr. Ayako Umemura (Futaba Project), Dr. Yoko Sakata (Kobe University), Mr. Kebi Chen (Daikin Industries, Ltd.), Ms. Nao Horike, Dr. Mikhail Meilikhov (SCOPION Management Consultants), Dr. Manuel Tsotsalas (The Karlsruhe Institute of Technology), Ms. Kira Khaletskaya (Ruhr-Universität Bochum), Mr. Chiwon Kim, Dr. Kenji Sumida, Mr. Kenji Yoshida for their valuable suggestions and kind technical supports.
The author expresses his gratitude to Dr. Hiroshi Sato, Dr. Daisuke Tanaka (Osaka University), Dr. Hirotoshi Sakamoto (Shinshu University), Dr. Maw Lin Foo, Dr.
Munehiro Inukai, Dr. Satoru Shimomura, Dr. Yu Hijikata, Mr. Keiji Nakagawa, Mr.
Keisuke Kishida, Mr. Kohei Nakamura, Mr. Ryo Ohtani, Mr. Tomohiro Fukushima, Mr.
Daiki Umeyama, for their valuable discussions. The author wishes to express his hurtful gratitude to all the members of Kitagawa group.
The author is much indebted for the financial support of Research Fellowship of the Japan Society for the Promotion of Science for Young Scientists. Finally, the author wishes to offer special thanks to his parents, Yoshiyuki Hirai and Machiko Hirai, and his brother Shin-ichiro Hirai for constant financial supports and warm-hearted encouragements.
Chapter 1. Heterogeneously Hybridized Porous Coordination Polymer Crystals:
Fabrication of Heterometallic Core–Shell Single Crystals with an In-Plane
Chapter 3. Sequential Functionalization of Porous Coordination Polymer Crystals 45
Chapter 6. Multilength-scales structuralization emerged from one reaction 93 Chapter 7.
Redox Reaction in Two-Dimensional Porous Coordination Polymers
Chapter 8. Crystal Orientation Controls Analyte Detection Kinetics of Porous Coordination Polymer Hybrid Sensor with Quartz Oscillator 135
1. Structuralization of Materials Chemistry is the art of manipulating bonds, interactions, and arrangements of atoms in a controlled and reproducible fashion. A wide variety of chemical reactions allows us to precisely design the molecular structures. In contrast, chemistry is now evolving away from the manipulation of individual molecules and toward the control of complex systems like living cells or materials. This evolution toward complexity bridges molecular chemistry and macroscopic science, thus opening a way for further development of molecular-based materials.
The properties of solid-state materials are determined by two structures across different length scales, chemical and macroscale structures. The chemical structures (individual molecular structures or arrangement of molecules) determine their inherent properties. In addition to the properties originating from chemical structures, the macroscale structures (size, morphology and structural hierarchy) often endow further properties with the materials. In particular, nanomaterials and photonic crystals are representative examples, in which macroscale structures significantly contribute to their properties. Downsizing the metallic compounds into nanometer-scale produces a band gap energy, so-called quantum effect,1 and leads to characteristic optical2 and electronic properties.3 In another case, the periodic nanostructures affect the propagation of electromagnetic waves and result in the characteristic optical properties.4-5 These phenomena are strongly depends on the macroscale structures of materials rather than the chemical structures. As seen in the examples provided above, control of macroscale structures of materials expands the range of practical applications and opens a way for new scientific areas.
Considerable effort has been devoted to the development of method to design the macroscale structures of a variety of materials. The solid-state materials can be remodeled in two main ways through bottom-up chemistry and top-down engineering 1 strategies. The bottom-up approaches involve ordinary chemical synthesis, template synthesis and assembly of the materials. On the other hand, laser, heating or mechanical processing methods are categorized into the top-down approaches. Both approaches can be applied to materials, if the materials are strong enough to endure harsh conditions of top-down approaches. In general, molecular materials comprising of weak chemical bonds, are often not stable under such harsh conditions of top-down approaches. In that sense, chemical approaches are the promising way to design both of chemical and macroscale structures of molecular materials.
22. Porous Coordination Polymers
The discovery of new solid-state materials has been considered as one of most critical factors in developing science and technology. In recent years, inorganic-organic hybrid materials, which composed of metal ions as connectors and organic ligands as linkers, have been emerged as a new class of porous solids, so-called porous coordination polymers (PCPs) or metal organic frameworks (MOFs). PCPs have been extensively studied not only for the scientific interest but also for the commercial interest in their applications for molecular storage,6-8 separation,9-10 catalysis,11-13 polymerization,14 and chemical sensing15-16. The remarkable progress of PCPs as functional materials is mainly due to the fact that compared to other conventional microporous materials (zeolites and activated carbons), PCPs are rationally designed based on the modifications of organic ligands and variation of coordination geometries. Therefore, these prominent features enables to precisely design the channel structures, pore sizes, and pore surface functionalities (Figure 1).
Figure 1. Porous coordination polymers (PCPs)
3 The inherent properties of PCPs are basically dominated by the chemical structures: pore size, pore surface functionality and framework topology. In that context, considerable effort has been devoted to synthesis of new compounds and evaluate these molecular-based properties at the early stage of this research field. In contrast, the macroscale structure is also one of crucial factors to sophisticate the properties, especially for separation efficiency, catalytic activity, and adsorption kinetics.17-18 Furthermore, the morphology and size of PCPs strongly influenced on the cooperative phenomena such as magnetic transition19 and structural transformation.20 (Figure 2)
Figure 2. Macroscale structured PCP
The well-designed macroscale architectures of PCPs are generated from the assembly of individual components (metal ions and organic ligands). Firstly, the molecular structures of individual organic ligands are designed and the proper metal ions are chosen. Secondly, the organization of metal centers by connecting them with organic linkers leads to the construction of crystalline microporous frameworks. Thirdly, the spatial control of this crystallization process results in the macroscale architectures of PCPs. This structural hierarchy from individual components to the macroscale architectures can be divided into three structural classifications (Figure 3).
Secondary structure: crystalline microporous framework composed of metal ions and organic ligands The self-assembly of metal ions and organic ligands results in construction of crystalline coordination frameworks. The coordination number of metal ions and molecular structures of organic ligands potentially determine the framework structures.
Ternary structure: Macroscale architectures of PCP crytals The control of the crystal morphology, spatial position or assembly of crystals enable to construct macroscale structures such as membranes,21-22 hollow particles,23 three-dimensional superstructures24 and hybrid particles.25-27 Figure 3. Structural hierarchy from individual components to macroscale strucuresof PCPs 5 The huge amount of accumulated knouledge in molecular chemistry and crystal engineering allows for designing the individual framework structures and crystalline particles; however, the development of methods to control the macroscale structures of PCPs are required in order to further sophisticate this material. Since PCPs are comprising of weak coordination bonds, top-down approaches including laser, heating and mechanical processing methods are often not suitable for fabricating the macroscale structures of PCPs. To control the macroscale structures of PCPs, three bottom-up approaches could be employed; chemical synthesis, templating and crystal assembly (Figure 4).
63. Macroscale structuraliztaion of PCPs
Since PCPs are comprising of weak coordination bonds, top-down approaches including laser, heating and mechanical processing methods are not versatile method to fabricate the macroscale structures. Thus, three kinds of bottom-up approaches can be employed to design the macroscale structures of PCPs, chemical synthesis, templating and crystal assembly (Figure 3) Figure 4. Three bottom-up approaches for macroscale structured PCPs
3.1 Chemical Synthesis Controlling the size or morphology of PCP crystals have attracted much attention due to the size-dependent characteristics for a variety of applications, including catalysis, spin-crossover, biomedical imaging, and drug-delivery. Several distinct approaches have recently been undertaken by exploring the possibility of controlling the shape and size of PCP crystals.
·Additives One way to control the crystal size is adding functional molecules,28-29 which 7 influence on the coordination equilibrium. Such additives like polymers and monofunctional molecules coordinate to metal ions or stabilize the precursors during nucleation or growth processes, consequently, the crystal size and morphology of PCPs are well controlled. For instances, uniform-sized PCP nanocrystals are fabricated;
so-called coordination modulation method;29 by altering the coordination equilibrium at the crystal surface during the growth process, through competitive interactions originating from a capping additive (modulator) with the same chemical functionality as the framework linker.
·Confined crystallization Another technique for the preparation of nanocrystals is to spatially confine the crystallization. Water-in-oil,30 or reverse microemulsions31 are highly tailorable systems that consist of nanometer-sized water droplets stabilized by a surfactant in a predominantly organic phase. The micelles in the microemulsion essentially serve as “nanoreactors” that spatially restrict the particle formation. Thanks to the confinement of crystallization, the uniform-sized particles are obtained.
·Instrument-assisted reaction Furthermore, some apparatus such as microwave and ultrasonicator are utilized for controlling the crystallization. The microwave-32 and ultrasound-assisted methods33 allow for the synthesis of nanocrystals. However, the size, shape and dimensionality of the nanocrystals are often not precisely controlled by using these methods. Hence, ultrasound-assisted methods combining with microemulsion has been developed to particles.34 prevent the formation of amorphous coordination polymer The microwave-assisted conditions with coordination modulation method35 is also a promising way to prepare the uniform-sized crystals with keeping the crystallinity.
One of key principles to fabricate macroscale architectures is to control the spatial positions of the materials. Thus, spatial control of PCP crystals is traditionally performed by using templates, which induce the crystallization or support the architectures of deposited crystals. The increasing number of reports that focus on the processing of PCPs into thin films, two-dimensional patterns and spheres accounts for the significance of their integration into directly applicable materials.