Co-reporter:Takayuki Yamamoto, Hirokazu Kobayashi, Loku Singgappulige Rosantha Kumara, Osami Sakata, Kiyofumi Nitta, Tomoya Uruga, and Hiroshi Kitagawa
Nano Letters September 13, 2017 Volume 17(Issue 9) pp:5273-5273
Publication Date(Web):August 14, 2017
DOI:10.1021/acs.nanolett.7b01535
Bulk silver iodide (AgI) is known to show a phase transition from the poorly conducting β/γ-phases into the superionic conducting α-phase at 147 °C. Its transition temperature decreases with decreasing the size of AgI, and the α-phase exists stably at 37 °C in AgI nanoparticles with a diameter of 6.3 nm. In this Letter, we investigated the atomic configuration, the phase transition behavior, and the ionic conductivity of AgI nanoparticles with a diameter of 3.0 nm. The combination of pair distribution function (PDF) analysis and reverse Monte Carlo (RMC) modeling based on high-energy X-ray diffraction (XRD) revealed for the first time that they formed the β/γ-phases with atomic disorder. The results of extended X-ray absorption fine structure (EXAFS) analysis, differential scanning calorimetry (DSC), and AC impedance spectroscopy demonstrated that they did not exhibit the superionic phase transition and their ionic conductivity was lower than that of crystalline AgI. The disappearance of the superionic phase transition and low ionic conductivity in the very small AgI nanoparticles originates from their small size and disordered structure.Keywords: EXAFS analysis; pair distribution function analysis; phase transition; reverse Monte Carlo modeling; Silver iodide;
Co-reporter:Shun Sakaida, Tomoyuki Haraguchi, Kazuya Otsubo, Osami Sakata, Akihiko Fujiwara, and Hiroshi Kitagawa
Inorganic Chemistry July 17, 2017 Volume 56(Issue 14) pp:7606-7606
Publication Date(Web):June 29, 2017
DOI:10.1021/acs.inorgchem.7b01113
We report the fabrication and characterization of the first example of a tetracyanonickelate-based two-dimensional-layered metal–organic framework, {Fe(py)2Ni(CN)4} (py = pyridine), thin film. To fabricate a nanometer-sized thin film, we utilized the layer-by-layer method, whereby a substrate was alternately soaked in solutions of the structural components. Surface X-ray studies revealed that the fabricated film was crystalline with well-controlled growth directions both parallel and perpendicular to the substrate. In addition, lattice parameter analysis indicated that the crystal system is found to be close to higher symmetry by being downsized to a thin film.
Co-reporter:Bo Huang, Hirokazu Kobayashi, Tomokazu Yamamoto, Syo Matsumura, Yoshihide Nishida, Katsutoshi Sato, Katsutoshi Nagaoka, Shogo Kawaguchi, Yoshiki Kubota, and Hiroshi Kitagawa
Journal of the American Chemical Society April 5, 2017 Volume 139(Issue 13) pp:4643-4643
Publication Date(Web):March 24, 2017
DOI:10.1021/jacs.7b01186
We report on novel solid-solution alloy nanoparticles (NPs) of Ru and Cu that are completely immiscible even above melting point in bulk phase. Powder X-ray diffraction, scanning transmission electron microscopy, and energy-dispersive X-ray measurements demonstrated that Ru and Cu atoms were homogeneously distributed in the alloy NPs. Ru0.5Cu0.5 NPs demonstrated higher CO oxidation activity than fcc-Ru NPs, which are known as one of the best monometallic CO oxidation catalysts.
Co-reporter:Takayuki Yamamoto, Mitsuhiko Maesato, Naohisa Hirao, Saori I. Kawaguchi, Shogo Kawaguchi, Yasuo Ohishi, Yoshiki Kubota, Hirokazu Kobayashi, and Hiroshi Kitagawa
Journal of the American Chemical Society 2017 Volume 139(Issue 4) pp:1392-1395
Publication Date(Web):January 17, 2017
DOI:10.1021/jacs.6b11379
We performed variable-temperature synchrotron powder X-ray diffraction measurements and impedance spectroscopy under pressure for silver iodide (AgI) nanoparticles with a diameter of 11 nm. The superionic conducting α-phase of AgI nanoparticles was successfully stabilized down to at least 20 °C by applying a pressure of 0.18 GPa, whereas the transition temperature was 147 °C in bulk AgI at ambient pressure. To our knowledge, this is the first example of the α-phase of AgI existing stably at room temperature.
Co-reporter:Dilip Kumar Maity, Kenichi Otake, Saheli Ghosh, Hiroshi KitagawaDebajyoti Ghoshal
Inorganic Chemistry 2017 Volume 56(Issue 3) pp:
Publication Date(Web):January 17, 2017
DOI:10.1021/acs.inorgchem.6b02674
Five sulfonic acid group functionalized mixed ligand coordination polymers (CPs), namely, {[Zn(bpeH)(5-sip)(H2O)]·(H2O)}n (1), {[Cu(pyz)(5-Hsip)(H2O)2]·(H2O)2}n (2), {[Cu(bpee)0.5(5-sip)(H2O)2]·(H2O)4(bpeeH2)0.5}n (3), {[Cu(bpy)(5-Hsip)(H2O)]·(H2O)2}n (4), and {[Cu(bpy)2(5-H2sip)2]·(H2O)6}n (5) [where sip3– = 5-sulfoisophthalate; bpe = 4,4′-bispyridylethane; pyz = pyrazine; bpee = 4,4′-bispyridylethylene; bpy = 4,4′-bipyridine], have been synthesized with varying different N,N′-donor linkers using slow diffusion techniques at room temperature. The CPs possess guest water filled 1D channels and noncoordinating sulfonic acid or coordinated sulfonate groups, which are interconnected by means of extended intermolecular H-bonding interaction, which supports the humidity dependent proton conductivity of the samples. Under 95% relative humidity (% RH), the CPs exhibit the temperature dependent proton conductivity which is maximum up to in the range of ∼10–5–10–6 S cm–1 at 65 °C. In most of the cases, the framework shows activation energies with the value ranging from 0.35 to 0.54 eV, suggesting mostly the contribution of the Grotthuss mechanism of the proton conductivity.
Co-reporter:Yuki Watanabe;Tomoyuki Haraguchi;Kazuya Otsubo;Osami Sakata;Akihiko Fujiwara
Chemical Communications 2017 vol. 53(Issue 73) pp:10112-10115
Publication Date(Web):2017/09/12
DOI:10.1039/C7CC03828C
We report a step-by-step route to fabricate the first example of a crystalline oriented metal–organic framework thin film having an anionic inorganic pillar ligand, {Cu(4,4′-bipyridyl)2(SiF6)}. X-ray study and sorption analysis revealed its high crystallinity and porous character.
Co-reporter:Kazuya Otsubo, Tomoyuki Haraguchi, Hiroshi Kitagawa
Coordination Chemistry Reviews 2017 Volume 346(Volume 346) pp:
Publication Date(Web):1 September 2017
DOI:10.1016/j.ccr.2017.03.022
•An overview of crystalline architectures utilizing Hofmann-type MOFs at the nanoscale.•Thin film fabrication and nanoscale patterning by means of step-by-step technique.•Crystalline oriented thin films confirmed by X-ray diffraction study.•Crystal-downsizing effects observed in nanoparticles and thin films.•Potential uses for future optical, electronic and sensing device applications.Metal–organic frameworks (MOFs) have been of particular interest to researchers because of their structural designability, robustness, and rich science arising from uniform porosity. Among them, Hofmann-type MOFs, which are one of the earliest examples of a MOF, have been intensively studied. For the bulk state of Hofmann-type MOFs, their spin transition behavior induced by guest molecules and external stimuli has long been discussed as a key subject. On the other hand, the use of Hofmann-type MOFs as a nanoscale architecture has recently attracted significant attention toward future practical applications, such as stimuli-responsive sensors and switching devices. In this review, we present an overview of the recent development of fabrication of crystalline architectures at the nanoscale including thin films and nanoparticles utilizing Hofmann-type MOFs.Download high-res image (287KB)Download full-size image
Co-reporter:Tomoyuki Haraguchi, Kazuya Otsubo, Osami Sakata, Akihiko FujiwaraHiroshi Kitagawa
Journal of the American Chemical Society 2016 Volume 138(Issue 51) pp:16787-16793
Publication Date(Web):December 12, 2016
DOI:10.1021/jacs.6b10913
Fabrication of thin films made of metal–organic frameworks (MOFs) has been intensively pursued for practical applications that use the structural response of MOFs. However, to date, only physisorption-induced structural response has been studied in these films. Chemisorption can be expected to provide a remarkable structural response because of the formation of bonds between guest molecules and reactive metal sites in host MOFs. Here, we report that chemisorption-induced two-way structural transformation in a nanometer-sized MOF thin film. We prepared a two-dimensional layered-type MOF Fe[Pt(CN)4] thin film using a step-by-step approach. Although the as-synthesized film showed poor crystallinity, the dehydrated form of this thin film had a highly oriented crystalline nature (Film-D) as confirmed by synchrotron X-ray diffraction (XRD). Surprisingly, under water and pyridine vapors, Film-D showed chemisorption-induced dynamic structural transformations to Fe(L)2[Pt(CN)4] thin films [L = H2O (Film-H), pyridine (Film-P)], where water and pyridine coordinated to the open Fe2+ site. Dynamic structural transformations were also confirmed by in situ XRD, sorption measurement, and infrared reflection absorption spectroscopy. This is the first report of chemisorption-induced dynamic structural response in a MOF thin film, and it provides useful insights, which would lead to future practical applications of MOFs utilizing chemisorption-induced structural responses.
Co-reporter:Masaaki Sadakiyo, Teppei Yamada, Kenichi Kato, Masaki Takata and Hiroshi Kitagawa
Chemical Science 2016 vol. 7(Issue 2) pp:1349-1356
Publication Date(Web):05 Nov 2015
DOI:10.1039/C5SC03325J
Closed–open structural transformations in flexible metal–organic frameworks (MOFs) are of interest for potential applications such as separation, because of their complete selectivity for the adsorption of specific guest molecules. Here, we report the control of the adsorption behaviour in a series of flexible MOFs, (H2dab)[M2(ox)3] (H2dab = 1,4-diammoniumbutane, M = Fe, Co, Ni, Zn, or Mg), having different central metals with analogous crystal structures. We found that a significant change in the selective adsorption behaviour for EtOH over MeCHO and MeCN is caused by the type of central metals, without changes in the crystal structures of all phases (except the Ni compound). A systematic study of adsorption measurements and structural analyses of the analogous MOFs reveals for the first time that the framework flexibility around the central metals of MOFs is truly related to the selective adsorption behaviour.
Co-reporter:Tomoyuki Haraguchi, Kazuya Otsubo, Osami Sakata, Shogo Kawaguchi, Akihiko Fujiwara and Hiroshi Kitagawa
Chemical Communications 2016 vol. 52(Issue 35) pp:6017-6020
Publication Date(Web):01 Apr 2016
DOI:10.1039/C6CC00056H
We describe the synthesis and sorption properties of a new metal–organic framework (MOF), Fe(H2O)2(bpy)[Pt(CN)4]·H2O (bpy = 4,4′-bipyridine), with a three-dimensional accordion-like structure. Although crystalline oriented MOF thin films reported to date have been mainly limited to a layer-type structure, we succeeded in the fabrication of its crystalline oriented thin film.
Co-reporter:Ken-ichi Otake, Kazuya Otsubo, Kunihisa Sugimoto, Akihiko Fujiwara, and Hiroshi Kitagawa
Inorganic Chemistry 2016 Volume 55(Issue 5) pp:2620-2626
Publication Date(Web):February 22, 2016
DOI:10.1021/acs.inorgchem.5b02980
One-dimensional (1D) electronic systems have attracted significant attention for a long time because of their various physical properties. Among 1D electronic systems, 1D halogen-bridged mixed-valence transition-metal complexes (the so-called MX chains) have been thoroughly studied owing to designable structures and electronic states. Here, we report the syntheses, structures, and electronic properties of three kinds of novel neutral MX-chain complexes. The crystal structures consist of 1D chains of Pt–X repeating units with (1R,2R)-(−)-diaminocychlohexane and CN– in-plane ligands. Because of the absence of a counteranion, the neutral MX chains have short interchain distances, so that strong interchain electronic interaction is expected. Resonance Raman spectra and diffuse-reflectance UV–vis spectra indicate that their electronic states are mixed-valence states (charge-density-wave state: Pt2+···X–Pt4+–X···Pt2+···X–Pt4+–X···). In addition, the relationship between the intervalence charge-transfer (IVCT) band gap and the degree of distortion of the 1D chain shows that the neutral MX chains have a larger IVCT band gap than that of cationic MX-chain complexes. These results provide new insight into the physical and electronic properties of 1D chain compounds.
Co-reporter:Mikihiro HayashiKazuya Otsubo, Mitsuhiko Maesato, Tokutaro Komatsu, Kunihisa Sugimoto, Akihiko Fujiwara, Hiroshi Kitagawa
Inorganic Chemistry 2016 Volume 55(Issue 24) pp:13027-13034
Publication Date(Web):December 6, 2016
DOI:10.1021/acs.inorgchem.6b02301
An electrically conductive D–A–D aggregate composed of a single component was first constructed by use of a protonated bimetal dithiolate (complex 1H2). The crystal structure of complex 1H2 has one-dimensional (1-D) π-stacking columns where the D and A moieties are placed in a segregated-stacking manner. In addition, these segregated-stacking 1-D columns are stabilized by hydrogen bonds. The result of a theoretical band calculation suggests that a conduction pathway forms along these 1-D columns. The transport property of complex 1H2 is semiconducting (Ea = 0.29 eV, ρrt = 9.1 × 104 Ω cm) at ambient pressure; however, the resistivity becomes much lower upon applying high pressure up to 8.8 GPa (Ea = 0.13 eV, ρrt = 6.2 × 10 Ω cm at 8.8 GPa). The pressure dependence of structural and optical changes indicates that the enhancement of conductivity is attributed to not only an increase of π–π overlapping but also a unique pressure-induced intramolecular charge transfer from D to A moieties in this D–A–D aggregate.
Co-reporter:Hirokazu Kobayashi, Yuko Mitsuka, and Hiroshi Kitagawa
Inorganic Chemistry 2016 Volume 55(Issue 15) pp:7301
Publication Date(Web):June 20, 2016
DOI:10.1021/acs.inorgchem.6b00911
Hybrid materials composed of metal nanoparticles and metal–organic frameworks (MOFs) have attracted much attention in many applications, such as enhanced gas storage and catalytic, magnetic, and optical properties, because of the synergetic effects between the metal nanoparticles and MOFs. In this Forum Article, we describe our recent progress on novel synthetic methods to produce metal nanoparticles covered with a MOF (metal@MOF). We first present Pd@copper(II) 1,3,5-benzenetricarboxylate (HKUST-1) as a novel hydrogen-storage material. The HKUST-1 coating on Pd nanocrystals results in a remarkably enhanced hydrogen-storage capacity and speed in the Pd nanocrystals, originating from charge transfer from Pd nanocrystals to HKUST-1. Another material, Pd–Au@Zn(MeIM)2 (ZIF-8, where HMeIM = 2-methylimidazole), exhibits much different catalytic activity for alcohol oxidation compared with Pd–Au nanoparticles, indicating a design guideline for the development of composite catalysts with high selectivity. A composite material composed of Cu nanoparticles and Cr3F(H2O)2O{C6H3(CO2)3}2 (MIL-100-Cr) demonstrates higher catalytic activity for CO2 reduction into methanol than Cu/γ-Al2O3. We also present novel one-pot synthetic methods to produce composite materials including Pd/ZIF-8 and Ni@Ni2(dhtp) (MOF-74, where H4dhtp = 2,5-dihydroxyterephthalic acid).
Co-reporter:Dr. Masaaki Sadakiyo;Dr. Teppei Yamada; Hiroshi Kitagawa
ChemPlusChem 2016 Volume 81( Issue 8) pp:691-701
Publication Date(Web):
DOI:10.1002/cplu.201600243
Abstract
Recent investigations into proton conduction in metal–organic frameworks (MOFs) indicate that MOFs are promising materials as a new class of proton conductors. Hydrated proton-conductive MOFs show not only high proton conductivity of approximately 10−2 S cm−1, which is comparable to that of a practical organic polymer, but also structural visibility of proton-conducting pathways inside the materials owing to their high crystallinity. Herein, studies on the design, synthesis, and proton-conductive properties of MOFs with hydrated proton-conductive systems are introduced.
Co-reporter:Hirokazu Kobayashi, Kohei Kusada, and Hiroshi Kitagawa
Accounts of Chemical Research 2015 Volume 48(Issue 6) pp:1551
Publication Date(Web):May 20, 2015
DOI:10.1021/ar500413e
Currently 118 known elements are represented in the periodic table. Of these 118 elements, only about 80 elements are stable, nonradioactive, and widely available for our society. From the viewpoint of the “elements strategy”, we need to make full use of the 80 elements to bring out their latent ability and create innovative materials. Furthermore, there is a strong demand that the use of rare or toxic elements be reduced or replaced while their important properties are retained. Advanced science and technology could create higher-performance materials even while replacing or reducing minor or harmful elements through the combination of more abundant elements.The properties of elements are correlated directly with their electronic states. In a solid, the magnitude of the density of states (DOS) at the Fermi level affects the physical and chemical properties. In the present age, more attention has been paid to improving the properties of materials by means of alloying elements. In particular, the solid-solution-type alloy is advantageous because the properties can be continuously controlled by tuning the compositions and/or combinations of the constituent elements. However, the majority of bulk alloys are of the phase-separated type under ambient conditions, where constituent elements are immiscible with each other. To overcome the challenge of the bulk-phase metallurgical aspects, we have focused on the nanosize effect and developed methods involving “nonequilibrium synthesis” or “a process of hydrogen absorption/desorption”. We propose a new concept of “density-of-states engineering” for the design of materials having the most desirable and suitable properties by means of “interelement fusion”.In this Account, we describe novel solid-solution alloys of Pd–Pt, Ag–Rh, and Pd–Ru systems in which the constituent elements are immiscible in the bulk state. The homogeneous solid-solution alloys of Pd and Pt were created from Pd core/Pt shell nanoparticles using a hydrogen absorption/desorption process as a trigger. Several atom percent replacements of Pd with Pt atoms resulted in a significantly enhanced hydrogen absorption capacity compared with Pd nanoparticles. AgxRh1–x and PdxRu1–x solid-solution alloy nanoparticles were also developed by nonequilibrium synthesis based on a polyol method. The AgxRh1–x nanoparticles demonstrated hydrogen storage properties, although pure metal nanoparticles of each constituent element do not adsorb hydrogen. AgxRh1–x is therefore considered to possess a similar electronic structure to Pd as a synthetic pseudo-palladium. The PdxRu1–x nanoparticles showed enhanced catalytic activity for CO oxidation, with the highest catalytic activity found using the equimolar Pd0.5Ru0.5 nanoparticles. The catalytic activity of the Pd0.5Ru0.5 nanoparticles exceeds that of the widely used and best-performing Ru catalysts for CO oxidation and is also higher than that of neighboring Rh on the periodic table. Our present work provides a guiding principle for the design of a suitable DOS shape according to the intended physical and/or chemical properties and a method for the development of novel solid-solution alloys.
Co-reporter:Jared M. Taylor; Tokutaro Komatsu; Shun Dekura; Kazuya Otsubo; Masaki Takata
Journal of the American Chemical Society 2015 Volume 137(Issue 35) pp:11498-11506
Publication Date(Web):August 24, 2015
DOI:10.1021/jacs.5b07267
Understanding the role that crystal imperfections or defects play on the physical properties of a solid material is important for any application. In this report, the highly unique crystal structure of the metal–organic framework (MOF) zirconium 2-sulfoterephthalate is presented. This MOF contains a large number of partially occupied ligand and metal cluster sites which directly affect the physical properties of the material. The partially occupied ligand positions give rise to a continuum of pore sizes within this highly porous MOF, supported by N2 gas sorption and micropore analysis. Furthermore, this MOF is lined with sulfonic acid groups, implying a high proton concentration in the pore, but defective zirconium clusters are found to be effective proton trapping sites, which was investigated by a combination of AC impedance analysis to measure the proton conductivity and DFT calculations to determine the solvation energies of the protons in the pore. Based on the calculations, methods to control the pKa of the clusters and improve the conductivity by saturating the zirconium clusters with strong acids were utilized, and a 5-fold increase in proton conductivity was achieved using these methods. High proton conductivity of 5.62 × 10–3 S cm–1 at 95% relative humidity and 65 °C could be achieved, with little change down to 40% relative humidity at room temperature.
Co-reporter:Kazuyuki Fujie, Ryuichi Ikeda, Kazuya Otsubo, Teppei Yamada, and Hiroshi Kitagawa
Chemistry of Materials 2015 Volume 27(Issue 21) pp:7355
Publication Date(Web):October 14, 2015
DOI:10.1021/acs.chemmater.5b02986
Metal–organic frameworks (MOFs) are desirable host materials to study and control the dynamics of molecules and ions such as lithium ions. We show the first study of a lithium ion-doped ionic liquid (IL) incorporated into a MOF and investigate its phase behavior and ionic conductivity. Moreover, for the first time, we have studied the dynamics of lithium ions in the micropores of the MOF in terms of the self-diffusion coefficient of the lithium ions. The IL was a mixture of EMI-TFSA (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide) with LiTFSA (lithium bis(trifluoromethylsulfonyl)amide), and the MOF was ZIF-8 (Zn(MeIM)2; H(MeIM) = 2-methylimidazole). The TFSA– anions showed a gradual decrease of mobility in the micropores at low temperatures, which indicates the absence of the apparent freezing transition. The mobility of the Li+ cations showed a slightly steeper decrease than that of the TFSA– anions at low temperature. The ionic conductivity of the (EMI0.8Li0.2)TFSA in the micropores was 2 orders of magnitude lower than that of the bulk (EMI0.8Li0.2)TFSA. However, the activation energy for the diffusion of lithium ions in the micropores of ZIF-8 was comparable with the bulk (EMI0.8Li0.2)TFSA. These results suggest that the Li+ cations diffuse through the micropores via the exchange of the solvating TFSA– anions, similar to the Grotthuss mechanism in proton conductivity.
Co-reporter:Jared M. Taylor, Shun Dekura, Ryuichi Ikeda, and Hiroshi Kitagawa
Chemistry of Materials 2015 Volume 27(Issue 7) pp:2286
Publication Date(Web):March 20, 2015
DOI:10.1021/acs.chemmater.5b00665
Co-reporter:Kazuyuki Fujie, Kazuya Otsubo, Ryuichi Ikeda, Teppei Yamada and Hiroshi Kitagawa
Chemical Science 2015 vol. 6(Issue 7) pp:4306-4310
Publication Date(Web):05 May 2015
DOI:10.1039/C5SC01398D
Ionic liquids (ILs) show promise as safe electrolytes for electrochemical devices. However, the conductivity of ILs decreases markedly at low temperatures because of strong interactions arising between the component ions. Metal–organic frameworks (MOFs) are appropriate microporous host materials that can control the dynamics of ILs via the nanosizing of ILs and tunable interactions of MOFs with the guest ILs. Here, for the first time, we report on the ionic conductivity of an IL incorporated within a MOF. The system studied consisted of EMI-TFSA (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide) and ZIF-8 (Zn(MeIM)2, H(MeIM) = 2-methylimidazole) as the IL and the MOF, respectively. While the ionic conductivity of bulk EMI-TFSA showed a sharp decrease arising from freezing, the EMI-TFSA@ZIF-8 showed no marked decrease because there was no phase transition. The ionic conductivity of EMI-TFSA@ZIF-8 was higher than that of bulk EMI-TFSA below 250 K. This result points towards a novel method by which to design electrolytes for electrochemical devices such as batteries that can operate at low temperatures.
Co-reporter:Xun-Gao Liu, Song-Song Bao, Jian Huang, Kazuya Otsubo, Jian-Shen Feng, Min Ren, Feng-Chun Hu, Zhihu Sun, Li-Min Zheng, Shiqiang Wei and Hiroshi Kitagawa
Chemical Communications 2015 vol. 51(Issue 82) pp:15141-15144
Publication Date(Web):20 Aug 2015
DOI:10.1039/C5CC05647K
A new type of homochiral metal–organic nanotubular structures based on metal phosphonates are reported, namely, (R)- or (S)-[M(pemp)(H2O)2][M = CoII (1), NiII (2)] [pemp2− = (R)- or (S)-(1-phenylethylamino)methylphosphonate]. In these compounds, the tube-walls are purely inorganic, composed of metal ions and O–P–O bridges. The cavity of the nanotube is hydrophilic with one coordination water pointing towards the center, while the outer periphery of the nanotube is hydrophobic, decorated by the phenylethyl groups of pemp2−. The thermal stabilities, adsorption and proton conductivity properties are investigated.
Co-reporter:Mikihiro Hayashi, Kazuya Otsubo, Tatsuhisa Kato, Kunihisa Sugimoto, Akihiko Fujiwara and Hiroshi Kitagawa
Chemical Communications 2015 vol. 51(Issue 87) pp:15796-15799
Publication Date(Web):04 Sep 2015
DOI:10.1039/C5CC06149K
We present the first report of a compact, planar and low-energy-gap molecule based on a π-conjugated bimetal system comprising a tetrathiooxalate (tto) skeleton. The observed low HOMO–LUMO energy gap (1.19 eV) is attributed to its donor–acceptor–donor (D–A–D) nature because the tto skeleton acts as an electron acceptor as well as a tiny and noninnocent bridging moiety.
Co-reporter:Megumi Mukoyoshi, Hirokazu Kobayashi, Kohei Kusada, Mikihiro Hayashi, Teppei Yamada, Mitsuhiko Maesato, Jared M. Taylor, Yoshiki Kubota, Kenichi Kato, Masaki Takata, Tomokazu Yamamoto, Syo Matsumura and Hiroshi Kitagawa
Chemical Communications 2015 vol. 51(Issue 62) pp:12463-12466
Publication Date(Web):06 Jul 2015
DOI:10.1039/C5CC04663G
We demonstrate a novel, simple synthetic method for metal (Ni) NPs in a MOF using the partial thermal decomposition of nickel(II) 2,5-dihydroxyterephthalate (Ni-MOF-74). The Ni NPs inside the Ni-MOF-74 are several nanometers in size, and the size can be precisely controlled by the heating conditions.
Co-reporter:Tomoyuki Haraguchi; Kazuya Otsubo; Osami Sakata; Akihiko Fujiwara
Inorganic Chemistry 2015 Volume 54(Issue 24) pp:11593-11595
Publication Date(Web):December 7, 2015
DOI:10.1021/acs.inorgchem.5b02207
Highly oriented crystalline thin films of metal–organic frameworks (MOFs) have promising practical applications, such as in gas separation, catalysis, and sensing. We report on the successful fabrication of highly oriented crystalline thin films of three-dimensional porous MOFs, Fe(pz)[M(CN)4] (M = Ni, Pd; pz = pyrazine). Synchrotron X-ray diffraction studies reveal not only the highly oriented crystalline nature but also the remarkable shrunken structure of the thin films (∼3–7% volume shrinkage) compared with bulk samples. Furthermore, because of lattice shrinkage, these films exhibit large lattice expansions upon guest adsorption, in marked contrast to the almost unchanged lattice in the bulk samples.
Co-reporter:Hisashi O̅kawa; Masaaki Sadakiyo; Kazuya Otsubo; Ko Yoneda; Teppei Yamada; Masaaki Ohba
Inorganic Chemistry 2015 Volume 54(Issue 17) pp:8529-8535
Publication Date(Web):August 17, 2015
DOI:10.1021/acs.inorgchem.5b01176
Proton conduction of the LaIIIMIII compounds, LaM(ox)3·10H2O (abbreviated to LaM; M = Cr, Co, Ru, La; ox2– = oxalate) is studied in view of their networks. LaCr and LaCo have a ladder structure, and the ladders are woven to form a channel network. LaRu and LaLa have a honeycomb sheet structure, and the sheets are combined to form a layer network. The occurrence of these structures is explained by the rigidness versus flexibility of [M(ox)3]3– in the framework with large LaIII. The channel networks of LaCr and LaCo show a remarkably high proton conductivity, in the range from 1 × 10–6 to 1 × 10–5 S cm–1 over 40–95% relative humidity (RH) at 298 K, whereas the layer networks of LaCr and LaCo show a lower proton conductivity, ∼3 × 10–8 S cm–1 (40–95% RH, 298 K). Activation energy measurements demonstrate that the channels filled with water molecules serve as efficient pathways for proton transport. LaCo was gradually converted to LaIIICoII(ox)2.5·4H2O, which had no channel structure and exhibited a low proton conductivity of less than 1 × 10–10 S cm–1. The conduction–network correlation of LaCo(ox)2.5·4H2O is reported.
Co-reporter:Song-Song Bao ; Kazuya Otsubo ; Jared M. Taylor ; Zheng Jiang ; Li-Min Zheng
Journal of the American Chemical Society 2014 Volume 136(Issue 26) pp:9292-9295
Publication Date(Web):June 19, 2014
DOI:10.1021/ja505916c
We report that a new 2D 3d–4f phosphonate [CoIIILaIII(notpH)(H2O)6]ClO4·5H2O (CoLa-II) can undergo a phase transition above 45 °C and 93% relative humidity, resulting in [H3O][CoLa(notp)(H2O)4]ClO4·3H2O (CoLa-III). The transition is accompanied by the release of the proton from intralayer to interlayer, and thus the proton conductivity of the material is increased by 1 order of magnitude.
Co-reporter:Guangqin Li, Hirokazu Kobayashi, Shun Dekura, Ryuichi Ikeda, Yoshiki Kubota, Kenichi Kato, Masaki Takata, Tomokazu Yamamoto, Syo Matsumura, and Hiroshi Kitagawa
Journal of the American Chemical Society 2014 Volume 136(Issue 29) pp:10222-10225
Publication Date(Web):July 14, 2014
DOI:10.1021/ja504699u
Pd octahedrons and cubes enclosed by {111} and {100} facets, respectively, have been synthesized for investigation of the shape effect on hydrogen-absorption properties. Hydrogen-storage properties were investigated using in situ powder X-ray diffraction, in situ solid-state 2H NMR and hydrogen pressure–composition isotherm measurements. With these measurements, it was found that the exposed facets do not affect hydrogen-storage capacity; however, they significantly affect the absorption speed, with octahedral nanocrystals showing the faster response. The heat of adsorption of hydrogen and the hydrogen diffusion pathway were suggested to be dominant factors for hydrogen-absorption speed. Furthermore, in situ solid-state 2H NMR detected for the first time the state of 2H in a solid-solution (Pd + H) phase of Pd nanocrystals at rt.
Co-reporter:Masaaki Sadakiyo ; Teppei Yamada
Journal of the American Chemical Society 2014 Volume 136(Issue 38) pp:13166-13169
Publication Date(Web):September 8, 2014
DOI:10.1021/ja507634v
Proton conductivity through two-dimensional (2-D) hydrogen-bonding networks within a layered metal–organic framework (MOF) (NH4)2(H2adp)[Zn2(ox)3]·3H2O (H2adp = adipic acid; ox = oxalate) has been successfully controlled by cation substitution. We synthesized a cation-substituted MOF, K2(H2adp)[Zn2(ox)3]·3H2O, where the ammonium ions in a well-defined hydrogen-bonding network are substituted with non-hydrogen-bonding potassium ions, without any apparent change in the crystal structure. We successfully controlled the proton conductivity by cleavage of the hydrogen bonds in a proton-conducting pathway, showing that the 2-D hydrogen-bonding networks in the MOF truly contribute to the high proton conductivity. This is the first example of the control of proton conductivity by ion substitution in a well-defined hydrogen-bonding network within a MOF.
Co-reporter:Masaaki Sadakiyo ; Teppei Yamada ; Kyohei Honda ; Hiroshi Matsui
Journal of the American Chemical Society 2014 Volume 136(Issue 21) pp:7701-7707
Publication Date(Web):May 2, 2014
DOI:10.1021/ja5022014
Structure-defined metal–organic frameworks (MOFs) are of interest because rational design and construction allow us to develop good proton conductors or possibly control the proton conductivity in solids. We prepared a highly proton-conductive MOF (NH4)2(adp)[Zn2(ox)3]·nH2O (abbreviated to 1·nH2O, adp: adipic acid, ox: oxalate, n = 0, 2, 3) having definite crystal structures and showing reversible structural transformations among the anhydrate (1), dihydrate (1·2H2O), and trihydrate (1·3H2O) phases. The crystal structures of all of these phases were determined by X-ray crystallography. Hydrogen-bonding networks consisting of ammonium ions, water molecules, and carboxylic acid groups of the adipic acids were formed inside the two-dimensional interlayer space in hydrated 1·2H2O and 1·3H2O. The crystal system of 1 or 1·2H2O (P21/c, No. 14) was changed into that of 1·3H2O (P1̅, No. 2), depending on water content because of rearrangement of guests and acidic molecules. Water molecules play a key role in proton conduction as conducting media and serve as triggers to change the proton conductivity through reforming hydrogen-bonding networks by water adsorption/desorption processes. Proton conductivity was consecutively controlled in the range from ∼10–12 S cm–1 (1) to ∼10–2 S cm–1 (1·3H2O) by the humidity. The relationships among the structures of conducting pathways, adsorption behavior, and proton conductivity were investigated. To the best of our knowledge, this is the first example of the control of a crystalline proton-conducting pathway by guest adsorption/desorption to control proton conductivity using MOFs.
Co-reporter:Kohei Kusada ; Hirokazu Kobayashi ; Ryuichi Ikeda ; Yoshiki Kubota ; Masaki Takata ◇◆; Shoichi Toh ; Tomokazu Yamamoto ; Syo Matsumura ; Naoya Sumi ; Katsutoshi Sato ; Katsutoshi Nagaoka
Journal of the American Chemical Society 2014 Volume 136(Issue 5) pp:1864-1871
Publication Date(Web):January 23, 2014
DOI:10.1021/ja409464g
PdxRu1–x solid solution alloy nanoparticles were successfully synthesized over the whole composition range through a chemical reduction method, although Ru and Pd are immiscible at the atomic level in the bulk state. From the XRD measurement, it was found that the dominant structure of PdxRu1–x changes from fcc to hcp with increasing Ru content. The structures of PdxRu1–x nanoparticles in the Pd composition range of 30–70% consisted of both solid solution fcc and hcp structures, and both phases coexist in a single particle. In addition, the reaction of hydrogen with the PdxRu1–x nanoparticles changed from exothermic to endothermic as the Ru content increased. Furthermore, the prepared PdxRu1–x nanoparticles demonstrated enhanced CO-oxidizing catalytic activity; Pd0.5Ru0.5 nanoparticles exhibit the highest catalytic activity. This activity is much higher than that of the practically used CO-oxidizing catalyst Ru and that of the neighboring Rh, between Ru and Pd.
Co-reporter:Guangqin Li, Hirokazu Kobayashi, Kohei Kusada, Jared M. Taylor, Yoshiki Kubota, Kenichi Kato, Masaki Takata, Tomokazu Yamamoto, Syo Matsumura and Hiroshi Kitagawa
Chemical Communications 2014 vol. 50(Issue 89) pp:13750-13753
Publication Date(Web):24 Sep 2014
DOI:10.1039/C4CC05941G
Presented here is the synthesis of an ordered bcc copper–palladium nanoalloy, via the decomposition of a Pd nanoparticle@metal–organic framework composite material. In situ XRD measurements were performed in order to understand the mechanism of the decomposition process. This result gives a further perspective into the synthesis of new nanomaterials via metal–organic framework decomposition.
Co-reporter:Kazuya Otsubo, Atsushi Kobayashi, Kunihisa Sugimoto, Akihiko Fujiwara, and Hiroshi Kitagawa
Inorganic Chemistry 2014 Volume 53(Issue 2) pp:1229-1240
Publication Date(Web):January 6, 2014
DOI:10.1021/ic402846v
Ladder systems situated in a crossover from one dimensionality to two dimensionalities have been an attractive research target, because the physical properties, which are associated with dimensionality, are strongly dependent on the number of constituent legs. However, control of the intraladder configuration and electronic properties based on the substitution of structural components remain challenging tasks in materials science. On the other hand, structural design using coordination chemistry offers crucial advantages for architectural and electronic variations through substitutions of metal–organic building blocks. Here, we show the rational design and electronic properties of novel metal complex-based two-legged ladder compounds with several organic rung units: 4,4′-bipyridine, trans-1,4-diaminocyclohexane, and 4,4′-azopyridine. Single-crystal X-ray studies show that these two-legged ladder compounds are composed of halogen-bridged mixed-valence one-dimensional chains (MX chains) as their constituent legs. Depending on the molecular shape of the organic rung units, unique configurations of two-legged ladder lattices with periodic distortion of the legs are achieved. In addition, the electronic absorption spectra show that intervalence charge-transfer (IVCT) band gap of the two-legged ladder system increases with increasing degree of distortion of the leg. We have demonstrated for the first time that a two-legged ladder system shows a unique relationship between IVCT energy and the distortion parameter of the leg, as distinct from a single MX chain system. These systematic investigations, not only of configurations based on the rung variation but also of electronic states in metal–organic ladder system, provide the possibility for wide and rational tunings of physical and electronic properties of metal complex-based functional materials.
Co-reporter:Rie Makiura, Hiroshi Kitagawa, Yasuyuki Akita, Mamoru Yoshimoto
Journal of Colloid and Interface Science 2014 Volume 413() pp:71-77
Publication Date(Web):1 January 2014
DOI:10.1016/j.jcis.2013.09.024
•Molecular-based nanoarrays are assembled on solid surfaces via coordinative bonding.•Nanoarrays are grown in a step-by-step manner.•The solubility of the molecular units is an important parameter to tune array size.•The domain growth is influenced by the molecule–substrate interaction.We report the development of a solution-based step-by-step technique, which utilizes the coordination bond between metalloporphyrin molecular units and metal linkages and results in the nuclear growth of nano-networks on solid substrates. The growth of the surface structures is strongly influenced by the choice of substrate materials and solvents: the molecule–substrate interaction and the solubility of the molecular units are important parameters in tuning the size and growth of the domains.
Co-reporter:Susan Sen, Teppei Yamada, Hiroshi Kitagawa, and Parimal K. Bharadwaj
Crystal Growth & Design 2014 Volume 14(Issue 3) pp:1240-1244
Publication Date(Web):January 14, 2014
DOI:10.1021/cg401760m
A novel entangled architecture formed on solvothermal reaction of a imidazolium based bent ligand with Cd(NO3)2, showing 1D channels decorated with imidazolium groups, is reported. The polymer, {[Cd2(L)3(DMF)(NO3)](DMF)3(H2O)8}n (1) (where H2L = 1,3-bis(4-carboxyphenyl)imidazolium, DMF = dimethylformamide), shows an interesting 6,3-connected polycatenated structure with channels along the crystallographic b-axis occupied with large number of DMF and water molecules. On removal of these solvent molecules the compound maintains its overall structure. Proton conductivity investigation affords a proton conductivity of 1.3 × 10–5 Scm–1 at 25 °C and 98% RH when water molecules are introduced into the empty channels.
Co-reporter:Kazuya Otsubo and Hiroshi Kitagawa
CrystEngComm 2014 vol. 16(Issue 28) pp:6277-6286
Publication Date(Web):04 Jun 2014
DOI:10.1039/C4CE00634H
Ladder materials situated in a dimensional crossover region have attracted significant attention because of their unique physical properties, which depend strongly on the number of their constituent legs. Among them, metal–organic halogen-bridged ladder systems are currently of particular interest. These new series of ladder materials are composed of two or four halogen-bridged transition-metal complexes, the so-called MX-chains, as legs that are connected to each other by organic rung units. To date, a variety of two- and four-legged halogen-bridged ladder compounds, called MX-ladders, have been synthesized. We present an overview of design strategies, crystal structures, and unique electronic properties of MX-ladder materials with even numbers of legs. Utilization of coordination chemistry provides a high number of structural and electronic degrees of freedom, a striking feature of the MX-ladder system compared with transition-metal-oxide ladder systems. Not only their structural features including tunability via rung substitution but also their unique electronic properties depending on the number of legs and electronic states have recently been revealed.
Co-reporter:Kazuyuki Fujie;Dr. Teppei Yamada; Ryuichi Ikeda; Hiroshi Kitagawa
Angewandte Chemie International Edition 2014 Volume 53( Issue 42) pp:11302-11305
Publication Date(Web):
DOI:10.1002/anie.201406011
Abstract
Controlling the dynamics of ionic liquids (ILs) is a significant issue for widespread use. Metal–organic frameworks (MOFs) are ideal host materials for ILs because of their small micropores and tunable host–guest interactions. Herein, we demonstrate the first example of an IL incorporated within the micropores of a MOF. The system studied consisted of EMI-TFSA (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide) and ZIF-8 (composed of Zn(MeIM)2; H(MeIM)=2-methylimidazole) as the IL and MOF, respectively. Construction of the EMI-TFSA in ZIF-8 was confirmed by X-ray powder diffraction, nitrogen gas adsorption, and infrared absorption spectroscopy. Differential scanning calorimetry and solid-state NMR measurements showed that the EMI-TFSA inside the micropores demonstrated no freezing transition down to 123 K, whereas bulk EMI-TFSA froze at 231 K. Such anomalous phase behavior originates from the nanosize effect of the MOF on the IL. This result provides a novel strategy for stabilizing the liquid phase of the ILs down to a lower temperature region.
Co-reporter:Dr. Takashi Kajiwara;Dr. Masakazu Higuchi;Daisuke Watanabe;Dr. Hideyuki Higashimura;Dr. Teppei Yamada;Dr. Hiroshi Kitagawa
Chemistry - A European Journal 2014 Volume 20( Issue 47) pp:15611-15617
Publication Date(Web):
DOI:10.1002/chem.201403542
Abstract
To establish a strategy for designing porous coordination polymers (PCPs) for ammonia capture, the first systematic study on the stability of PCPs against ammonia was conducted. Various types of PCPs were investigated by comparing their powder XRD patterns before and after treatment with ammonia. Among the PCPs tested, ZIF-8, MIL-53(Al), Al-BTB, MOF-76(M) (M=Y or Yb), MIL-101(Cr), and MOF-74(Mg) were stable up to 350 °C under an ammonia atmosphere at ambient pressure. The origin of the stability of PCPs is discussed from the viewpoint of their components, metal cations, and organic linkers. Furthermore, adsorption isotherm measurements show that the adsorptive behavior of PCPs is independent of their stability.
Co-reporter:Teppei Yamada, Kazuya Otsubo, Rie Makiura and Hiroshi Kitagawa
Chemical Society Reviews 2013 vol. 42(Issue 16) pp:6655-6669
Publication Date(Web):01 Jul 2013
DOI:10.1039/C3CS60028A
Coordination polymers (CPs) have large degrees of freedom in framework compositions and in the structures and environment of the inner pores. This review focuses on the recent significant progress achieved by controlling these degrees of freedom. Two breakthroughs are reviewed for constructing sophisticated structures of CP frameworks, especially in dimensional crossover regions. The first is the synthesis of quasi one-dimensional halogen-bridged coordinative tubes by applying state-of-the-art techniques of coordination chemistry. The electronic state of the coordinative tube was studied by structural, spectroscopic and theoretical methods and found to be distinct from conventional one-dimensional systems. The second breakthrough is the achievement of a quasi-two-dimensional architecture by combining Langmuir–Blodgett and layer-by-layer methods. Two-dimensional LB CP films were prepared on liquid; the films were stacked layer by layer, and a crystalline quasi-two-dimensional structure was constructed. This review also covers the design of the environment of the inner pore, where hydrogen bond networks with various acidic sites were modified. By appropriate design of the hydrogen bond network, proton-conductive CPs are invented, which are summarized in this review. Types of proton donor sites are discussed and classified, and superprotonic conductive CPs were achieved in these investigations. These results will provide new strategies for constructing functional materials for smart devices.
Co-reporter:Hisashi O̅kawa ; Masaaki Sadakiyo ; Teppei Yamada ; Mitsuhiko Maesato ; Masaaki Ohba
Journal of the American Chemical Society 2013 Volume 135(Issue 6) pp:2256-2262
Publication Date(Web):January 9, 2013
DOI:10.1021/ja309968u
Proton-conductive magnetic metal–organic frameworks (MOFs), {NR3(CH2COOH)}[MaIIMbIII(ox)3] (abbreviated as R–MaMb: R = ethyl (Et), n-butyl (Bu); MaMb = MnCr, FeCr, FeFe) have been studied. The following six MOFs were prepared: Et–MnCr·2H2O, Et–FeCr·2H2O, Et–FeFe·2H2O, Bu–MnCr, Bu–FeCr, and Bu–FeFe. The structure of Bu–MnCr was determined by X-ray crystallography. Crystal data: trigonal, R3c (#161), a = 9.3928(13) Å, c = 51.0080(13) Å, Z = 6. The crystal consists of oxalate-bridged bimetallic layers interleaved by {NBu3(CH2COOH)}+ ions. Et–MnCr·2H2O and Bu–MnCr (R–MnCr MOFs) show a ferromagnetic ordering with TC of 5.5–5.9 K, and Et–FeCr·2H2O and Bu–FeCr (R–FeCr MOFs) also show a ferromagnetic ordering with TC of 11.0–11.5 K. Et–FeFe·2H2O and Bu–FeFe (R–FeFe MOFs) belong to the class II of mixed-valence compounds and show the magnetism characteristic of Néel N-type ferrimagnets. The Et-MOFs (Et–MnCr·2H2O, Et–FeCr·2H2O and Et–FeFe·2H2O) show high proton conduction, whereas the Bu–MOFs (Bu–MnCr, Bu–FeCr, and Bu–FeFe) show moderate proton conduction. Together with water adsorption isotherm studies, the significance of the carboxyl residues as proton carriers is revealed. The R–MnCr MOFs and the R–FeCr MOFs are rare examples of coexistent ferromagnetism and proton conduction, and the R–FeFe MOFs are the first examples of coexistent Néel N-type ferrimagnetism and proton conduction.
Co-reporter:Gang Xu ; Kazuya Otsubo ; Teppei Yamada ; Shun Sakaida
Journal of the American Chemical Society 2013 Volume 135(Issue 20) pp:7438-7441
Publication Date(Web):May 7, 2013
DOI:10.1021/ja402727d
The electrical properties of a highly oriented crystalline MOF nanofilm were studied. This nanofilm has low activation energy and a proton conductivity that is among the highest value reported for MOF materials. The study uncovered the reasons for the excellent performance of this nanofilm and revealed a new pathway for proton transport in MOF materials; besides the channels inside a MOF, the surface of the MOF nanocrystal can also dominate proton transport.
Co-reporter:Kohei Kusada ; Hirokazu Kobayashi ; Tomokazu Yamamoto ; Syo Matsumura ; Naoya; Sumi ; Katsutoshi Sato ; Katsutoshi Nagaoka ; Yoshiki Kubota
Journal of the American Chemical Society 2013 Volume 135(Issue 15) pp:5493-5496
Publication Date(Web):April 4, 2013
DOI:10.1021/ja311261s
We report the first discovery of pure face-centered-cubic (fcc) Ru nanoparticles. Although the fcc structure does not exist in the bulk Ru phase diagram, fcc Ru was obtained at room temperature because of the nanosize effect. We succeeded in separately synthesizing uniformly sized nanoparticles of both fcc and hcp Ru having diameters of 2–5.5 nm by simple chemical reduction methods with different metal precursors. The prepared fcc and hcp nanoparticles were both supported on γ-Al2O3, and their catalytic activities in CO oxidation were investigated and found to depend on their structure and size.
Co-reporter:Shuhei Yamasaki;Dr. Teppei Yamada;Dr. Hirokazu Kobayashi; Hiroshi Kitagawa
Chemistry – An Asian Journal 2013 Volume 8( Issue 1) pp:73-75
Publication Date(Web):
DOI:10.1002/asia.201200790
Co-reporter:Susan Sen ; Nisanth N. Nair ; Teppei Yamada ; Hiroshi Kitagawa ;Parimal K. Bharadwaj
Journal of the American Chemical Society 2012 Volume 134(Issue 47) pp:19432-19437
Publication Date(Web):November 6, 2012
DOI:10.1021/ja3076378
A novel metal–organic framework, [{(Zn0.25)8(O)}Zn6(L)12(H2O)29(DMF)69(NO3)2]n (1) {H2L = 1,3-bis(4-carboxyphenyl)imidazolium}, has been synthesized under solvothermal conditions in good yield. It shows a Zn8O cluster that is coordinated to six ligands and forms an overall three-dimensional structure with channels along the crystallographic a and b axes. The imidazolium groups of the ligand moiety are aligned in the channels. The channels are not empty but are occupied by a large number of DMF and water molecules. Upon heating, these solvent molecules can be removed without breakdown of the overall structure of the framework as shown by variable-temperature powder X-ray diffraction patterns. Of great interest is the fact that the compound exhibits high proton conductivity with a low activation energy that is comparable to those of Nafion presently used in fuel cells.
Co-reporter:Hirokazu Kobayashi ; Hitoshi Morita ; Miho Yamauchi ; Ryuichi Ikeda ; Hiroshi Kitagawa ⊗; Yoshiki Kubota ; Kenichi Kato ◆; Masaki Takata ◆; Shoichi Toh +;Syo Matsumura ⊗+
Journal of the American Chemical Society 2012 Volume 134(Issue 30) pp:12390-12393
Publication Date(Web):July 16, 2012
DOI:10.1021/ja305031y
We have synthesized and characterized homogeneous solid-solution alloy nanoparticles of Pd and Rh, which are immiscible with each other in the equilibrium bulk state at around room temperature. The Pd–Rh alloy nanoparticles can absorb hydrogen at ambient pressure and the hydrogen pressure of Pd–Rh alloys for hydrogen storage is dramatically decreased by more than 4 orders of magnitude from the corresponding pressure in the metastable bulk state. The solid-solution state is still maintained in the nanoparticles even after hydrogen absorption/desorption, in contrast to the metastable bulks which are separated into Pd and Rh during the process.
Co-reporter:Akihito Shigematsu ; Teppei Yamada
Journal of the American Chemical Society 2012 Volume 134(Issue 32) pp:13145-13147
Publication Date(Web):July 31, 2012
DOI:10.1021/ja306401j
A novel porous coordination polymer, CuII(mtpm)Cl2 [mtpm = tetrakis(m-pyridyloxy methylene)methane], has been synthesized, and its crystal structure has been determined. Its adsorption isotherms for water, methanol, and ethanol are totally different from each other. It adsorbs water at low humidity and shows gate-open behavior for methanol, but it does not adsorb ethanol. This compound has the capacity to separate both methanol and water from bioethanol, which is a mixture of water, methanol, and ethanol.
Co-reporter:Gang Xu ; Teppei Yamada ; Kazuya Otsubo ; Shun Sakaida
Journal of the American Chemical Society 2012 Volume 134(Issue 40) pp:16524-16527
Publication Date(Web):October 2, 2012
DOI:10.1021/ja307953m
The preparation of crystalline, ordered thin films of metal–organic frameworks (MOFs) will be a critical process for MOF-based nanodevices in the future. MOF thin films with perfect orientation and excellent crystallinity were formed with novel nanosheet-structured components, Cu–TCPP [TCPP = 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin], by a new “modular assembly” strategy. The modular assembly process involves two steps: a “modularization” step is used to synthesize highly crystalline “modules” with a nanosized structure that can be conveniently assembled into a thin film in the following “assembly” step. With this method, MOF thin films can easily be set up on different substrates at very high speed with controllable thickness. This new approach also enabled us to prepare highly oriented crystalline thin films of MOFs that cannot be prepared in thin-film form by traditional techniques.
Co-reporter:Masaaki Sadakiyo ; Hisashi O̅kawa ; Akihito Shigematsu ; Masaaki Ohba ; Teppei Yamada
Journal of the American Chemical Society 2012 Volume 134(Issue 12) pp:5472-5475
Publication Date(Web):March 12, 2012
DOI:10.1021/ja300122r
We controlled the hydrophilicity of metal–organic frameworks (MOFs) to achieve high proton conductivity and high adsorption of water under low humidity conditions, by employing novel class of MOFs, {NR3(CH2COOH)}[MCr(ox)3]·nH2O (abbreviated as R-MCr, where R = Me (methyl), Et (ethyl), or Bu (n-butyl), and M = Mn or Fe): Me-FeCr, Et-MnCr, Bu-MnCr, and Bu-FeCr. The cationic components have a carboxyl group that functions as the proton carrier. The hydrophilicity of the cationic ions was tuned by the NR3 residue to decrease with increasing bulkiness of the residue: {NMe3(CH2COOH)}+ > {NEt3(CH2COOH)}+ > {NBu3(CH2COOH)}+. The proton conduction of the MOFs increased with increasing hydrophilicity of the cationic ions. The most hydrophilic sample, Me-FeCr, adsorbed a large number of water molecules and showed a high proton conductivity of ∼10–4 S cm–1, even at a low humidity of 65% relative humidity (RH), at ambient temperature. Notably, this is the highest conductivity among the previously reported proton-conducting MOFs that operate under low RH conditions.
Co-reporter:Hirokazu Kobayashi ; Miho Yamauchi
Journal of the American Chemical Society 2012 Volume 134(Issue 16) pp:6893-6895
Publication Date(Web):April 6, 2012
DOI:10.1021/ja302021d
We report nanosize-induced hydrogen storage in Ir, which does not absorb hydrogen in its bulk form. The mean diameter of the obtained Ir nanoparticles was estimated as 1.5 ± 0.5 nm by transmission electron microscopy. Hydrogen storage was confirmed by solid-state 2H NMR and hydrogen pressure–composition isotherm measurements.
Co-reporter:Kazuya Otsubo ; Tomoyuki Haraguchi ; Osami Sakata ; Akihiko Fujiwara
Journal of the American Chemical Society 2012 Volume 134(Issue 23) pp:9605-9608
Publication Date(Web):May 31, 2012
DOI:10.1021/ja304361v
Fabrication of a crystalline ordered thin film based on the porous metal–organic frameworks (MOFs) is one of the practical applications of the future functional nanomaterials. Here, we report the creation of a highly oriented three-dimensional (3-D) porous pillared-layer-type MOF thin film on a metal substrate using a step-by-step approach based on liquid-phase epitaxy. Synchrotron X-ray diffraction (XRD) study clearly indicates that the thin film is crystalline and its orientation is highly controlled in both horizontal and vertical directions relative to the substrate. This report provides the first confirmation of details of not only the crystallinity but also the orientation of 3-D MOF thin film using synchrotron XRD. Moreover, we also demonstrate its guest adsorption/desorption behavior by using in situ XRD measurements. The results presented here would promise useful insights for fabrication of MOF-based nanodevices in the future.
Co-reporter:Teppei Yamada and Hiroshi Kitagawa
CrystEngComm 2012 vol. 14(Issue 12) pp:4148-4152
Publication Date(Web):15 May 2012
DOI:10.1039/C2CE25358E
Protected phosphonate groups were embedded onto isophthalic acid and reacted with zinc ion to synthesize metal–organic frameworks (MOFs). Single-crystal X-ray diffraction measurement revealed the crystal structures of obtained MOFs under various temperatures and solvent conditions. The isopropyl groups were left protected when the complexation reaction was executed at 60 °C, while they were partially deprotected in the sample prepared at 120 °C. When the reaction was carried out at 180 °C, the isopropyl groups were totally deprotected. This result provides us with information on the deprotection reaction in a post-synthetic method for constructing MOFs.
Co-reporter:Soichiro Motoyama ; Rie Makiura ; Osami Sakata
Journal of the American Chemical Society 2011 Volume 133(Issue 15) pp:5640-5643
Publication Date(Web):March 30, 2011
DOI:10.1021/ja110720f
Layer-structured metal−organic framework (MOF) nanofilms (NAFS-2) consisting of 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin (H2TCPP) molecules and copper ion metal linkers were assembled on a gold or a silicon surface by applying a solution-based layer-by-layer growth technique coupled with the Langmuir−Blodgett method. Synchrotron X-ray diffraction measurements showed that NAFS-2 exhibits highly crystalline order in both the in-plane and out-of-plane orientations. Each MOF sheet (monolayer) adheres without pillaring units, and the nanofilm maintains its highly crystalline order above 200 °C. The results provide an excellent demonstration of how to exercise in a facile way fine control of the assembly of molecule-based hybrid objects and their thermal stability, which is a key issue for the future use of MOFs in potential applications in nanodevices.
Co-reporter:Masaaki Sadakiyo ; Teppei Yamada
Journal of the American Chemical Society 2011 Volume 133(Issue 29) pp:11050-11053
Publication Date(Web):July 1, 2011
DOI:10.1021/ja203291n
One of the dominant types of interactions between host and guest molecules is hydrogen-bonding, and these interactions can work selectively for a guest molecule. Here, we demonstrate a metal–organic framework (MOF) having both hydrogen-bonding donor and acceptor sites that are quite effective for selective sorption. The MOF selectively interacts with hydroxylic guests in contrast to aprotic hydrogen-bonding guests and shows a sorption selectivity for protic H2O, MeOH, and EtOH guests. Notably, this is the first compound that shows complete selectivity in adsorption not for MeCN and MeCHO but for EtOH, which has similar fundamental properties except for its proticity.
Co-reporter:Hirokazu Kobayashi ; Hitoshi Morita ; Miho Yamauchi ; Ryuichi Ikeda ; Hiroshi Kitagawa ; Yoshiki Kubota ; Kenichi Kato ◆;Masaki Takata ◆
Journal of the American Chemical Society 2011 Volume 133(Issue 29) pp:11034-11037
Publication Date(Web):June 27, 2011
DOI:10.1021/ja2027772
We report the first example of nanosize-induced hydrogen storage in a metal that does not absorb hydrogen in its bulk form. Rhodium particles with diameters of <10 nm were found to exhibit hydrogen-storage capability, while bulk Rh does not absorb hydrogen. Hydrogen storage was confirmed by in situ powder X-ray diffraction, solid-state 2H NMR, and hydrogen pressure–composition isotherm measurements. The hydrogen absorption capacity could be tuned by controlling the particle size.
Co-reporter:Akihito Shigematsu ; Teppei Yamada
Journal of the American Chemical Society 2011 Volume 133(Issue 7) pp:2034-2036
Publication Date(Web):February 1, 2011
DOI:10.1021/ja109810w
The proton conductivities of the porous coordination polymers M(OH)(bdc−R) [H2bdc = 1,4-benzenedicarboxylic acid; M = Al, Fe; R = H, NH2, OH, (COOH)2] were investigated under humid conditions. Good correlations among pKa, proton conductivity, and activation energy were observed. Fe(OH)(bdc−(COOH)2), having carboxy group and the lowest pKa, showed the highest proton conductivity and the lowest activation energy in this system. This is the first example in which proton conductivity has been widely controlled by substitution of ligand functional groups in an isostructural series.
Co-reporter:Kohei Kusada ; Miho Yamauchi ; Hirokazu Kobayashi ; Hiroshi Kitagawa ;Yoshiki Kubota
Journal of the American Chemical Society 2010 Volume 132(Issue 45) pp:15896-15898
Publication Date(Web):October 27, 2010
DOI:10.1021/ja107362z
Rh and Ag are the elements neighboring Pd, which is well known as a hydrogen-storage metal. Although Rh and Ag do not possess hydrogen-storage properties, can Ag−Rh alloys actually store hydrogen? Ag−Rh solid-solution alloys have not been explored in the past because they do not mix with each other at the atomic level, even in the liquid phase. We have used the chemical reduction method to obtain such Ag−Rh alloys, and XRD and STEM-EDX give clear evidence that the alloys mixed at the atomic level. From the measurements of hydrogen pressure−composition isotherms and solid-state 2H NMR, we have revealed that Ag−Rh solid-solution alloys absorb hydrogen, and the total amount of hydrogen absorbed reached a maximum at the ratio of Ag:Rh = 50:50, where the electronic structure is expected to be similar to that of Pd.
Co-reporter:Hirokazu Kobayashi ▽; Miho Yamauchi ◆; Hiroshi Kitagawa +; Yoshiki Kubota ; Kenichi Kato ;Masaki Takata
Journal of the American Chemical Society 2010 Volume 132(Issue 16) pp:5576-5577
Publication Date(Web):April 2, 2010
DOI:10.1021/ja1013163
We have achieved the creation of a solid-solution alloy where Pd and Pt are homogeneously mixed at the atomic level, by a process of hydrogen absorption/desorption as a trigger for core (Pd)/shell (Pt) nanoparticles. The structural change from core/shell to solid solution has been confirmed by in situ powder X-ray diffraction, energy dispersive spectra, solid-state 2H NMR measurement, and hydrogen pressure−composition isotherms. The successfully obtained Pd−Pt solid-solution nanoparticles with a Pt content of 8−21 atom % had a higher hydrogen-storage capacity than Pd nanoparticles. Moreover, the hydrogen-storage capacity of Pd−Pt solid-solution nanoparticles can be tuned by changing the composition of Pd and Pt.
Co-reporter:Rie Makiura
European Journal of Inorganic Chemistry 2010 Volume 2010( Issue 24) pp:3715-3724
Publication Date(Web):
DOI:10.1002/ejic.201000730
Abstract
Controlling the size and the growth direction of porous hybrid objects – metal–organic frameworks (MOFs) or porous coordination polymers (PCPs) – at the nanoscale is a critical issue for enabling their use in a number of potential applications that have arisen from the current remarkable activity in studying such porous materials. This microreview describes the recent progress in the design, growth, and characterization of multidimensional nanoarchitectures by employing porphyrin-based components. The versatility of the sequential bottom-up fabrication process, which uses multitopic molecular building units assembled by appropriately chosen linkers, is suitable to be extended to the formation of a rich variety of nanostructures endowed with pores on surfaces.
Co-reporter:Lifen Yang;Shozo Kinoshita;Teppei Yamada;Seiichi Ka ;Makoto Tokunaga ;Takayoshi Ishimoto;Teppei Ogura;Ryo Nagumo;Akira Miyamoto ;Michihisa Koyama
Angewandte Chemie International Edition 2010 Volume 49( Issue 31) pp:5348-5351
Publication Date(Web):
DOI:10.1002/anie.201000863
Co-reporter:Lifen Yang;Shozo Kinoshita;Teppei Yamada;Seiichi Ka ;Makoto Tokunaga ;Takayoshi Ishimoto;Teppei Ogura;Ryo Nagumo;Akira Miyamoto ;Michihisa Koyama
Angewandte Chemie 2010 Volume 122( Issue 31) pp:5476-5479
Publication Date(Web):
DOI:10.1002/ange.201000863
Co-reporter:Hisashi O̅kawa ; Akihito Shigematsu ; Masaaki Sadakiyo ; Takuya Miyagawa ; Ko Yoneda ; Masaaki Ohba
Journal of the American Chemical Society 2009 Volume 131(Issue 37) pp:13516-13522
Publication Date(Web):August 28, 2009
DOI:10.1021/ja905368d
The oxalate-bridged bimetallic complexes {NH(prol)3}[MIICrIII(ox)3] (MII = MnII, FeII, CoII) with hydrophilic tri(3-hydroxypropyl)ammonium (NH(prol)3+) were prepared by a new synthetic procedure, and the effects of the NH(prol)3+ ion upon the structure, magnetism, and electrical conduction were studied. An X-ray crystallographic study of the MnCr dihydrate, {NH(prol)3}[MnCr(ox)3]·2H2O, was performed. Crystal data: hexagonal, P63, a = b = 9.3808(14) Å, c = 15.8006(14) Å, Z = 2. The structure comprises oxalate-bridged bimetallic layers interleaved by NH(prol)3+ ions. The ions assume a tripodal configuration and are hydrogen bonded to the bimetallic layers together with water molecules, giving rise to a short interlayer separation (7.90 Å) and unsymmetrical faces to the bimetallic layer. Cryomagnetic studies demonstrate ferromagnetic ordering with transition temperature of 5.5 K for the MnCr complex, 9.0 K for the FeCr complex, and 10.0 K for the CoCr complex. The interlayer magnetic interaction is negligibly weak in all of the complexes despite the short interlayer separation. A slow magnetization is observed in all the complexes. This is explained by spin canting associated with the unsymmetrical feature of the bimetallic layer. The complexes show proton conduction of 1.2 × 10−10 to 4.4 × 10−10 S cm−1 under 40% relative humidity (RH) and ∼1 × 10−4 S cm−1 under 75% RH. On the basis of water adsorption/desorption profiles, the conduction under 40% RH is mediated through the hydrogen-bonded network formed by the bimetallic layer, NH(prol)3+ ions, and water molecules (two per MCr). Under 75% RH, additional water molecules (three per MCr) are concerned with the high proton conduction. This is the first example of a metal complex system exhibiting coexistent ferromagnetism and proton conduction.
Co-reporter:Masaaki Sadakiyo ; Teppei Yamada
Journal of the American Chemical Society 2009 Volume 131(Issue 29) pp:9906-9907
Publication Date(Web):July 6, 2009
DOI:10.1021/ja9040016
A novel metal−organic framework (MOF), (NH4)2(adp)[Zn2(ox)3]·3H2O (1) was synthesized and its structure was determined. We propose three types of rational design to introduce proton carriers into MOFs. The simplest method is to introduce them directly as counterions such as NH4+, H3O+, and HSO4− into the pores of frameworks (type I). The second is to put acid groups on frameworks, the protons being provided from them (type II). The third is to incorporate acidic molecules into voids (type III). 1 demonstrated a combination of two of the concepts by introducing NH4+ ions using the anionic framework (type I) and putting carboxyl end groups of adipic acid in a honeycomb-shaped void (type III). 1 showed a superprotonic conductivity of 10−2 S cm−1 at ambient temperature, comparable to organic polymers such as Nafion, which is in practical use in fuel cells. This is the first example of an MOF to exhibit a superprotonic conductivity of 10−2 S cm−1 at ambient temperature.
Co-reporter:Hirokazu Kobayashi, Miho Yamauchi, Ryuichi Ikeda and Hiroshi Kitagawa
Chemical Communications 2009 (Issue 32) pp:4806-4808
Publication Date(Web):02 Jul 2009
DOI:10.1039/B907875D
Size-controlled atomic-level Pd–Au alloy nanoparticles have been synthesized with a wide range of atomic ratios by a facile method using H2 gas, and their controllable hydrogen-absorption properties have been studied from hydrogen pressure–composition isotherms and solid-state 2H NMR spectra.
Co-reporter:Atsushi Kobayashi ; Shinji Kitao ; Makoto Seto ; Ryuichi Ikeda
Inorganic Chemistry 2009 Volume 48(Issue 16) pp:8044-8049
Publication Date(Web):July 16, 2009
DOI:10.1021/ic9007558
One-dimensional iodide-bridged mixed-valence binuclear platinum complexes (the so-called “MMX chains”) and their Pt(III) dimer precursors were investigated with 129I Mössbauer spectroscopy. Spectra consisting of two sets of octuplets were observed at low temperatures for a neutral MMX chain complex, Pt2(dtp)4I (dtp = C2H5CS2−), with various charge-ordering states at the Pt dimers, indicating that the charge-ordering state is in an alternate-charge-polarization phase (ACP: ···[Pt2+−Pt3+]−I0.4−−[Pt3+−Pt2+]···I0.3−···), which is consistent with a previous low-temperature X-ray diffraction study. The estimated valence states of the bridging iodines of [(C2H5)2NH2]4[Pt2(pop)4I] (pop = H2P2O52−), with a charge-polarization phase (CP: ···[Pt2+−Pt3+]−I0.4−···[Pt2+−Pt3+]−I0.4−···), and [H3N(CH2)6NH3]2[Pt2(pop)4I], with a charge-density-wave phase (CDW: ···[Pt2+−Pt2+]···I0.3−−[Pt3+−Pt3+]−I0.3−···), suggest that the covalent bond interaction is dominant in the CDW phase, whereas the Coulomb interaction is dominant in the CP phase. The estimated absolute quadrupole coupling constant (QCC) values for negatively charged MMX chain complexes with pop ligands are larger than those for neutral MMX chain complexes with CH3CS2− (dta) ligands, implying that the Madelung potential formed by the more-negative pop ligands and countercations effectively contributes to the physical properties of the pop system. The three Pt(III) dimer complexes Pt2(dta)4I2, Pt2(dtp)4I2, and K4[Pt2(pop)4I2] showed almost the same isomer shifts, indicating that the valence state of the iodide ion (I0.5−) depends negligibly on the terminal ligand. The QCC value observed for K4[Pt2(pop)4I2] was larger than those for Pt2(dta)4I2 and Pt2(dtp)4I2, originating from the anisotropic arrangement of the iodide anions, which form layers lying on the ab plane in the crystal.
Co-reporter:Miho Yamauchi Dr.;Hirokazu Kobayashi Dr. Dr.
ChemPhysChem 2009 Volume 10( Issue 15) pp:2566-2576
Publication Date(Web):
DOI:10.1002/cphc.200900289
Abstract
The hydrogen storage properties of metal nanoparticles change with particle size. For example, in a palladium–hydrogen system, the hydrogen solubility and equilibrium pressure for the formation of palladium hydride decrease with a decrease in the particle size, whereas hydrogen solubility in nanoparticles of platinum, in which hydrogen cannot be stored in the bulk state, increases. Systematic studies of hydrogen storage in Pd and Pt nanoparticles have clarified the origins of these nanosize effects. We found a novel hydrogen absorption site in the hetero-interface that forms between the Pd core and Pt shell of the Pd/Pt core/shell-type bimetallic nanoparticles. It is proposed that the potential formed in the hetero-interface stabilizes hydrogen atoms rather than interstitials in the Pd core and Pt shells. These results suggest that metal nanoparticles a few nanometers in size can act as a new type of hydrogen storage medium. Based on knowledge of the nanosize effects, we discuss how hydrogen storage media can be designed for improvement of the conditions of hydrogen storage.
Co-reporter:Tomoyuki Haraguchi, Kazuya Otsubo, Osami Sakata, Shogo Kawaguchi, Akihiko Fujiwara and Hiroshi Kitagawa
Chemical Communications 2016 - vol. 52(Issue 35) pp:NaN6020-6020
Publication Date(Web):2016/04/01
DOI:10.1039/C6CC00056H
We describe the synthesis and sorption properties of a new metal–organic framework (MOF), Fe(H2O)2(bpy)[Pt(CN)4]·H2O (bpy = 4,4′-bipyridine), with a three-dimensional accordion-like structure. Although crystalline oriented MOF thin films reported to date have been mainly limited to a layer-type structure, we succeeded in the fabrication of its crystalline oriented thin film.
Co-reporter:Megumi Mukoyoshi, Hirokazu Kobayashi, Kohei Kusada, Mikihiro Hayashi, Teppei Yamada, Mitsuhiko Maesato, Jared M. Taylor, Yoshiki Kubota, Kenichi Kato, Masaki Takata, Tomokazu Yamamoto, Syo Matsumura and Hiroshi Kitagawa
Chemical Communications 2015 - vol. 51(Issue 62) pp:NaN12466-12466
Publication Date(Web):2015/07/06
DOI:10.1039/C5CC04663G
We demonstrate a novel, simple synthetic method for metal (Ni) NPs in a MOF using the partial thermal decomposition of nickel(II) 2,5-dihydroxyterephthalate (Ni-MOF-74). The Ni NPs inside the Ni-MOF-74 are several nanometers in size, and the size can be precisely controlled by the heating conditions.
Co-reporter:Xun-Gao Liu, Song-Song Bao, Jian Huang, Kazuya Otsubo, Jian-Shen Feng, Min Ren, Feng-Chun Hu, Zhihu Sun, Li-Min Zheng, Shiqiang Wei and Hiroshi Kitagawa
Chemical Communications 2015 - vol. 51(Issue 82) pp:NaN15144-15144
Publication Date(Web):2015/08/20
DOI:10.1039/C5CC05647K
A new type of homochiral metal–organic nanotubular structures based on metal phosphonates are reported, namely, (R)- or (S)-[M(pemp)(H2O)2][M = CoII (1), NiII (2)] [pemp2− = (R)- or (S)-(1-phenylethylamino)methylphosphonate]. In these compounds, the tube-walls are purely inorganic, composed of metal ions and O–P–O bridges. The cavity of the nanotube is hydrophilic with one coordination water pointing towards the center, while the outer periphery of the nanotube is hydrophobic, decorated by the phenylethyl groups of pemp2−. The thermal stabilities, adsorption and proton conductivity properties are investigated.
Co-reporter:Mikihiro Hayashi, Kazuya Otsubo, Tatsuhisa Kato, Kunihisa Sugimoto, Akihiko Fujiwara and Hiroshi Kitagawa
Chemical Communications 2015 - vol. 51(Issue 87) pp:NaN15799-15799
Publication Date(Web):2015/09/04
DOI:10.1039/C5CC06149K
We present the first report of a compact, planar and low-energy-gap molecule based on a π-conjugated bimetal system comprising a tetrathiooxalate (tto) skeleton. The observed low HOMO–LUMO energy gap (1.19 eV) is attributed to its donor–acceptor–donor (D–A–D) nature because the tto skeleton acts as an electron acceptor as well as a tiny and noninnocent bridging moiety.
Co-reporter:Guangqin Li, Hirokazu Kobayashi, Kohei Kusada, Jared M. Taylor, Yoshiki Kubota, Kenichi Kato, Masaki Takata, Tomokazu Yamamoto, Syo Matsumura and Hiroshi Kitagawa
Chemical Communications 2014 - vol. 50(Issue 89) pp:NaN13753-13753
Publication Date(Web):2014/09/24
DOI:10.1039/C4CC05941G
Presented here is the synthesis of an ordered bcc copper–palladium nanoalloy, via the decomposition of a Pd nanoparticle@metal–organic framework composite material. In situ XRD measurements were performed in order to understand the mechanism of the decomposition process. This result gives a further perspective into the synthesis of new nanomaterials via metal–organic framework decomposition.
Co-reporter:Teppei Yamada, Kazuya Otsubo, Rie Makiura and Hiroshi Kitagawa
Chemical Society Reviews 2013 - vol. 42(Issue 16) pp:NaN6669-6669
Publication Date(Web):2013/07/01
DOI:10.1039/C3CS60028A
Coordination polymers (CPs) have large degrees of freedom in framework compositions and in the structures and environment of the inner pores. This review focuses on the recent significant progress achieved by controlling these degrees of freedom. Two breakthroughs are reviewed for constructing sophisticated structures of CP frameworks, especially in dimensional crossover regions. The first is the synthesis of quasi one-dimensional halogen-bridged coordinative tubes by applying state-of-the-art techniques of coordination chemistry. The electronic state of the coordinative tube was studied by structural, spectroscopic and theoretical methods and found to be distinct from conventional one-dimensional systems. The second breakthrough is the achievement of a quasi-two-dimensional architecture by combining Langmuir–Blodgett and layer-by-layer methods. Two-dimensional LB CP films were prepared on liquid; the films were stacked layer by layer, and a crystalline quasi-two-dimensional structure was constructed. This review also covers the design of the environment of the inner pore, where hydrogen bond networks with various acidic sites were modified. By appropriate design of the hydrogen bond network, proton-conductive CPs are invented, which are summarized in this review. Types of proton donor sites are discussed and classified, and superprotonic conductive CPs were achieved in these investigations. These results will provide new strategies for constructing functional materials for smart devices.
Co-reporter:Masaaki Sadakiyo, Teppei Yamada, Kenichi Kato, Masaki Takata and Hiroshi Kitagawa
Chemical Science (2010-Present) 2016 - vol. 7(Issue 2) pp:
Publication Date(Web):
DOI:10.1039/C5SC03325J
Co-reporter:Kazuyuki Fujie, Kazuya Otsubo, Ryuichi Ikeda, Teppei Yamada and Hiroshi Kitagawa
Chemical Science (2010-Present) 2015 - vol. 6(Issue 7) pp:NaN4310-4310
Publication Date(Web):2015/05/05
DOI:10.1039/C5SC01398D
Ionic liquids (ILs) show promise as safe electrolytes for electrochemical devices. However, the conductivity of ILs decreases markedly at low temperatures because of strong interactions arising between the component ions. Metal–organic frameworks (MOFs) are appropriate microporous host materials that can control the dynamics of ILs via the nanosizing of ILs and tunable interactions of MOFs with the guest ILs. Here, for the first time, we report on the ionic conductivity of an IL incorporated within a MOF. The system studied consisted of EMI-TFSA (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide) and ZIF-8 (Zn(MeIM)2, H(MeIM) = 2-methylimidazole) as the IL and the MOF, respectively. While the ionic conductivity of bulk EMI-TFSA showed a sharp decrease arising from freezing, the EMI-TFSA@ZIF-8 showed no marked decrease because there was no phase transition. The ionic conductivity of EMI-TFSA@ZIF-8 was higher than that of bulk EMI-TFSA below 250 K. This result points towards a novel method by which to design electrolytes for electrochemical devices such as batteries that can operate at low temperatures.
Co-reporter:Hirokazu Kobayashi, Miho Yamauchi, Ryuichi Ikeda and Hiroshi Kitagawa
Chemical Communications 2009(Issue 32) pp:
Publication Date(Web):
DOI:10.1039/B907875D
