Showing papers by "Susumu Kitagawa published in 2015"
TL;DR: The reversible solid-to-liquid phase transition of crystalline CPs is reported, and it is found that the coordination bonds are not fully preserved in the liquid state but are re-formed in the glass state.
Abstract: The solid-to-liquid phase transition, a fundamental process commonly observed for various types of substances with significant potential for application, has been given little attention in the field of coordination polymers (CPs) despite the rich functionality of these compounds. In this article, we report the reversible solid-to-liquid phase transition of crystalline CPs. These CPs are composed of zinc ions, phosphate, and azoles, and a well-balanced composition, ionicity, and bond strength afford "melting" CPs. We examined the structure of one such melting framework in the liquid and glass states and found that the coordination bonds are not fully preserved in the liquid state but are re-formed in the glass state. As a demonstration, we fabricated, via phase transition, a thin film with an aligned crystal orientation and a monolith crystal of the CP.
157 citations
TL;DR: The achievements in the field of metal-organic frameworks have rapidly and significantly advanced materials research that is vital to addressing energy and environmental issues.
Abstract: "… Materials that achieve mass storage and highly efficient separation of gases cannot be realized by simply improving conventional technology. The achievements in the field of metal-organic frameworks have rapidly and significantly advanced materials research that is vital to addressing energy and environmental issues…" Read more in the Editorial by Susumu Kitagawa.
127 citations
TL;DR: A rationally designed neutral and charge-polarized bridging ligand as a new partner for magnesium( II) and calcium(II) ions is reported, which allows the structural diversification of Group II magnesium(II] and calcium (II) PCPs.
Abstract: Inexpensive porous materials synthesized from Group II metals may be useful for industrial applications. Here, the authors demonstrate that neutral bridging ligands can be used for the synthesis of magnesium(II) and calcium(II) porous coordination polymers.
86 citations
TL;DR: Variation of the isostructures provides continuous changes in the local environment around the molecular rotors, leading to the control of the rotational frequency without the need to vary the temperature.
Abstract: Rational design to control the dynamics of molecular rotors in crystalline solids is of interest because it offers advanced materials with precisely tuned functionality. Herein, we describe the control of the rotational frequency of rotors in flexible porous coordination polymers (PCPs) using a solid-solution approach. Solid-solutions of the flexible PCPs [{Zn(5-nitroisophthalate)x(5-methoxyisophthalate)1–x(deuterated 4,4′-bipyridyl)}(DMF·MeOH)]n allow continuous modulation of cell volume by changing the solid-solution ratio x. Variation of the isostructures provides continuous changes in the local environment around the molecular rotors (pyridyl rings of the 4,4′-bipyridyl group), leading to the control of the rotational frequency without the need to vary the temperature.
68 citations
TL;DR: The preparation of ruthenium carbonyl-incorporated cross-linked hen egg white lysozyme crystals (Ru·CL-HEWL) shows potential for use as an artificial extracellular scaffold suitable for transport and release of a gas molecule.
Abstract: Protein crystals generally are stable solid protein assemblies. Certain protein crystals are suitable for use as nanovessels for immobilizing metal complexes. Here we report the preparation of ruthenium carbonyl-incorporated cross-linked hen egg white lysozyme crystals (Ru·CL-HEWL). Ru·CL-HEWL retains a Ru carbonyl moiety that can release CO, although a composite of Ru carbonyl-HEWL dissolved in buffer solution (Ru·HEWL) does not release CO. We found that treatment of cells with Ru·CL-HEWL significantly increased nuclear factor kappa B (NF-κB) activity as a cellular response to CO. These results demonstrate that Ru·CL-HEWL has potential for use as an artificial extracellular scaffold suitable for transport and release of a gas molecule.
67 citations
TL;DR: A new intelligent biochemical swimmer is created by integrating metal organic frameworks (MOFs) and peptides that can sense toxic heavy metals in solution and swim toward the targets.
Abstract: Highly efficient and robust chemical motors are expected for the application in microbots that can selectively swim toward targets and accomplish their tasks in sensing, labeling, and delivering. However, one of major issues for such development is that current artificial swimmers have difficulty controlling their directional motion toward targets like bacterial chemotaxis. To program synthetic motors with sensing capability for the target-directed motion, we need to develop swimmers whose motions are sensitive to chemical gradients in environments. Here we create a new intelligent biochemical swimmer by integrating metal organic frameworks (MOFs) and peptides that can sense toxic heavy metals in solution and swim toward the targets. With the aid of Pb-binding enzymes, the peptide-MOF motor can directionally swim toward PbSe quantum dots (QD) by sensing pH gradient and eventually complete the motion as the swimmer reaches the highest gradient point at the target position in solution. This type of technolo...
66 citations
TL;DR: A new protocol for the compatibilization of immiscible polymers at the molecular level using porous coordination polymers (PCPs) as removable templates is described, which results in a PSt/PMMA blend that is homogeneous in the range of several nanometers.
Abstract: The establishment of methodologies for the mixing of immiscible substances is highly desirable to facilitate the development of fundamental science and materials technology. Herein we describe a new protocol for the compatibilization of immiscible polymers at the molecular level using porous coordination polymers (PCPs) as removable templates. In this process, the typical immiscible polymer pair of polystyrene (PSt) and poly(methyl methacrylate) (PMMA) was prepared via the successive homopolymerizations of their monomers in a PCP to distribute the polymers inside the PCP particles. Subsequent dissolution of the PCP frameworks in a chelator solution affords a PSt/PMMA blend that is homogeneous in the range of several nanometers. Due to the unusual compatibilization, the thermal properties of the polymer blend are remarkably improved compared with the conventional solvent-cast blend. This method is also applicable to the compatibilization of PSt and polyacrylonitrile, which have very different solubility parameters.
60 citations
TL;DR: The accommodation of single polysilane chains with hole-transporting ability in porous coordination polymers (PCPs) did not exhibit photodegradation, highlighting that PCP-polysilane hybrids are promising candidates for further use in the field of molecular electronics.
Abstract: Understanding the intrinsic properties of single conducting polymer chains is of interest, largely for their applications in molecular devices. In this study, we report the accommodation of single polysilane chains with hole-transporting ability in porous coordination polymers (PCPs), [Al(OH)(L)]n (1a; L = 2,6-naphthalenedicarboxylate, channel size = 8.5 × 8.5 A2, 1b; L = 4,4′-biphenyldicarboxylate, channel size = 11.1 × 11.1 A2). Interestingly, the isolation of single polysilane chains increased the values of carrier mobility in comparison with that in the bulk state due to the elimination of the slow interchain hole hopping. Moreover, even when the chains are isolated one another, the main chain conformation of polysilane could be controlled by changing the pore environment of PCPs, as evidenced by Raman spectroscopy, solid-state NMR measurements, and molecular dynamics simulation. Hence, we succeeded in varying the conducting property of single polysilane chains. Additionally, polysilanes have a drawba...
60 citations
TL;DR: The synthesis of highly crystalline macro-meso-microporous monolithic Cu3(btc)2 (HKUST-1; btc(3-) = benzene-1,3,5-tricarboxylate) is demonstrated by direct conversion of Cu(OH)2-based monoliths while preserving the characteristic macroporous structure.
56 citations
TL;DR: Peptide-metal-organic framework motors, whose motions are driven by anisotropic surface tension gradients created via peptide self-assembly around frameworks, can rotate microscopic rotors and magnets fast enough to generate an electric power of 0.1 μW.
Abstract: Peptide-metal-organic framework (Pep-MOF) motors, whose motions are driven by anisotropic surface tension gradients created via peptide self-assembly around frameworks, can rotate microscopic rotors and magnets fast enough to generate an electric power of 0.1 μW. A new rigid Pep-MOF motor can be recycled by refilling the peptide fuel into the nanopores of the MOF.
54 citations
TL;DR: In this article, the authors employ the liquid phase epitaxial (LPE) growth strategy for the preparation of highly functional, hierarchically structured core-shell architectures consisting of [Zn4O(3,5-dialkylcarboxypyrazolate)3]n-based frameworks.
Abstract: Continuous stepwise liquid-phase epitaxial (LPE) growth is one of the most effective procedures for structuring metal–organic frameworks (MOFs) as two-dimensional superstructures, such as thin-films. Alternation of the building block precursors between the individual LPE growth cycles (i.e. from one linker to the other) allows heterostructured MOF films consisting of two different MOFs with different structural or chemical properties to be synthesized with a precise control of the growth sequence. Here, we employ the LPE growth strategy for the preparation of highly functional, hierarchically structured core–shell architectures consisting of [Zn4O(3,5-dialkylcarboxypyrazolate)3]n-based frameworks. Specifically, the small-pore [Zn4O(3-methyl-5-isopropyl-4-carboxypyrazolate)3]n (Zn-MI) and [Zn4O(3,5-diethyl-4-carboxypyrazolate)3]n (Zn-DE) frameworks are respectively deposited as a size selective layer upon larger-pore [Zn4O(3,5-dimethyl-4-carboxypyrazolate)3]n (Zn-DM) and [Zn4O(3-methyl-5-ethyl-4-carboxypyrazolate)3]n (Zn-ME) layers. Direct growth of the MOF layers on the Au surfaces of quartz crystal microbalance (QCM) sensors allowed the adsorption properties of the heterostructures to be probed in real-time. Multiple-component adsorption experiments in an environment-controlled QCM apparatus revealed size selectivity with respect to the adsorption of alcohols, as well as the molecular recognition of methanol over water. These properties stem from the positioning of the small-pore Zn-MI (or Zn-DE) layer on the larger-pore Zn-DM (or Zn-ME) layer, facilitating attractive synergistic properties for adsorptive selectivity and providing a possibility for further development in MOF-based sensing applications.
TL;DR: Control of the crystal size of porous heterogeneous catalysts, such as PCP/MOFs, offers a promising approach to fabricating high-performance catalysts based on accessibility to the internal catalytic sites.
TL;DR: In this paper, the coordination replication technique is employed for the direct conversion of a macro-and mesoporous Cu(OH)2-polyacrylamide composite to three-dimensional superstructures consisting of the flexible porous coordination polymers, Cu2(bdc)2(MeOH) 2 and Cu2[2]2(bpy) (bdc2− = 1,4-benzenedicarboxylate, bpy = 4,4′-bipyridine).
Abstract: The coordination replication technique is employed for the direct conversion of a macro- and mesoporous Cu(OH)2–polyacrylamide composite to three-dimensional superstructures consisting of the flexible porous coordination polymers, Cu2(bdc)2(MeOH)2 and Cu2(bdc)2(bpy) (bdc2− = 1,4-benzenedicarboxylate, bpy = 4,4′-bipyridine). Detailed characterization of the replicated systems reveals that the structuralization plays an important role in determining the adsorptive properties of the replicated systems, and that the immobilization of the crystals within a higher-order architecture also affects its structural and dynamic properties. The polyacrylamide polymer is also found to be crucial for maintaining the structuralization of the monolithic systems, and in providing the mechanical robustness required for manual handling. In all, the results discussed here demonstrate a significant expansion in the scope of the coordination replication strategy, and further confirms its utility as a highly versatile platform for the preparation of functional three-dimensional superstructures of porous coordination polymers.
TL;DR: It is found that the adsorbed gas molecules induced significant structural change involving dimensional change of the pore from one-dimensional to three-dimensional, and subsequently, additional gas molecules formed periodic molecular clusters in the nanospace.
Abstract: Direct observation of gas molecules confined in the nanospace of porous materials by single-crystal X-ray diffraction (SXRD) technique is significant because it leads to deep insight into the adsorption mechanism and the actual state of the adsorbents in molecular level. A recent study revealed that flexibility is one of the important factors to achieve periodic guest accommodation in the nanospace enabling direct observation of gas molecules. Here, we report a convenient strategy to tune the framework flexibility by just an atomic exchange in a ligand, which enables us to easily construct a soft nanospace as the best platform to study gas adsorption. Indeed, we succeeded to observe C2H2 and CO2 molecules confined in the pores of a flexible porous coordination polymer (PCP-N) in different configurations using SXRD measurement, whereas gas molecules in a rigid framework (PCP-C) isostructural to PCP-N were not seen crystallographically. The result of the coincident in situ powder X-ray diffraction and adsor...
TL;DR: The structure of a glass obtained by the melt quenching of a two-dimensional (2D) coordination network was examined, and a 2D-to-0D structural transformation before and after glass formation was disclosed.
TL;DR: The new microporous cobalt triazolyl phosphonate MOF3α exhibits exciting features including high water stability, reversible hydration-dehydration, steep water uptake in repeated cycles at low water vapor pressures and reactivation at room temperature under mild evacuation.
Abstract: The new microporous cobalt triazolyl phosphonate MOF 3α[Co4L3(μ3-OH)(H2O)3](SO4)0.5·xH2O (L2− = 4-(4H-1,2,4-triazol-4-yl)-phenyl phosphonate) exhibits exciting features including high water stability, reversible hydration–dehydration, steep water uptake in repeated cycles at low water vapor pressures and reactivation at room temperature under mild evacuation.
TL;DR: In this article, the authors have studied the dynamic behavior of oligomeric chain molecules, both theoretically and experimentally, in [Zn2(bdc)2(ted)]n (1; bdc = 1,4-benzenedicarboxylate, ted = triethylenediamine).
Abstract: The quest for porous coordination polymers (PCPs) has been the subject of intense research because of their unique porous functions. Although considerable attention has been paid to the behavior of gases and low-molecular-weight compounds in PCPs, the study of adsorption, diffusion, and interaction of macromolecules, including oligomers and polymers, in PCPs at the molecular level has been limited to date. Here, we have studied the dynamic behavior of oligomeric chain molecules, both theoretically and experimentally, in [Zn2(bdc)2(ted)]n (1; bdc = 1,4-benzenedicarboxylate, ted = triethylenediamine). Molecular dynamics simulations revealed that the motion of linear oligomeric chains, such as oligo(ethylene glycols) or paraffins, is composed of smooth transfer along the large channels and slow transfer to the adjacent channels by penetrating the narrow apertures of 1. Moreover, this anisotropic behavior depends on the polarity of the guest chains because of the Coulomb interactions with the polarized apertu...
TL;DR: A series of porous coordination polymers (PCPs) are synthesized, in which N-nitrosamine functional groups as photoactive NO donors were introduced into the framework scaffolds by post-synthetic nitrosation of amine functionalized analogous PCPs, which demonstrated a controlled release of NO from the PCPs by light irradiation.
Abstract: The development of nitric oxide (NO) releasing materials has been of significant importance due to their application in cell biology and biomedicine. Besides the macromolecular scaffold dangling NO releasing moiety, porous materials have been used to host such NO releasing molecules. Here we synthesized a series of porous coordination polymers (PCPs), in which N-nitrosamine functional groups as photoactive NO donors were introduced into the framework scaffolds by post-synthetic nitrosation of amine functionalized analogous PCPs. We further demonstrated a controlled release of NO from the PCPs by light irradiation. Though isoreticular frameworks based on octanuclear clusters of titanium or aluminium ions were chosen due to their water-stability, the frameworks showed difference in stability in cell culture media; while aluminium frameworks were less stable in water and physiological media, the titanium analogue was highly stable even under physiological conditions.
TL;DR: Porous Mg (2-methyl imidazolate)2 (Mg-ZIF-8) was synthesised from Mg(BH4)2 as a precursor under an Ar atmosphere and exhibits a Brunauer-Emmett-Teller surface area greater than 1800 m(2) g(-1).
Abstract: Porous Mg(2-methyl imidazolate)2 (Mg-ZIF-8) was synthesised from Mg(BH4)2 as a precursor under an Ar atmosphere. It possesses an uncommon tetrahedral Mg2+–N coordination geometry that is stabilised by the formation of a framework, and it exhibits a Brunauer–Emmett–Teller surface area greater than 1800 m2 g−1.
TL;DR: The present results corroborate similar findings observed on different systems and confirm that o–p conversion can occur on non-magnetic solids and that electric field can induce the catalytic hydrogen o-p conversion.
Abstract: The ability to design and control properties of nano-sized space in porous coordination polymers (PCPs) would provide us with an ideal stage for fascinating physical and chemical phenomena. We found an interconversion of nuclear-spin isomers for hydrogen molecule H2 adsorbed in a Hofmann-type PCP, {Fe(pz)[Pd(CN)4]} (pz=pyrazine), by the temperature dependence of Raman spectra. The ortho (o)–para (p) conversion process of H2 is forbidden for an isolated molecule. The charge density study using synchrotron radiation X-ray diffraction reveals the electric field generated in coordination nano-space. The present results corroborate similar findings observed on different systems and confirm that o–p conversion can occur on non-magnetic solids and that electric field can induce the catalytic hydrogen o–p conversion.
TL;DR: In this article, two-dimensional polycrystalline macrostructures and heterostructures made of [V(OH)ndc]n (ndc = 1,4-naphthalenedicarboxylate) PCP crystals were synthesized through a dissolution-recrystallization process, so-called coordination replication, where a pre-shaped V2O5 sacrificial phase was replaced by well-intergrown PCP crystal in the presence of H2ndc as an organic linker and under a reductive environment.
Abstract: Vanadium-based porous coordination polymers (or metal–organic frameworks) possess both porous and electronic properties, which make these new materials appealing for applications in molecular separation, sensing and heterogeneous catalysis. Their integration into systems that fully exploit their intrinsic properties requires versatile methods allowing assembly of the PCP crystals into well-defined films, patterns, fibers or the formation of heterostructures. In this contribution, polycrystalline macrostructures and heterostructures made of [V(OH)ndc]n (ndc = 1,4-naphthalenedicarboxylate) PCP crystals were synthesized through a dissolution–recrystallization process, so-called coordination replication, where a pre-shaped V2O5 sacrificial phase was replaced by well-intergrown PCP crystals in the presence of H2ndc as an organic linker and under a reductive environment. In this process, V2O5 acts both as the metal source and as the template that provides the shape to the resulting mesoscopic polycrystalline architecture. Ascorbic acid, acting as the reducing agent, both promotes the dissolution of the sacrificial V2O5 phase and provides the VIII species required for the construction of the [V(OH)ndc]n framework. Two-dimensional patterns were successfully synthesized by applying this procedure.
TL;DR: In this paper, a drastic increase in the proportion of methyl methacrylate units in the resulting copolymers was obtained compared with that obtained from the corresponding solution polymerization systems.
Abstract: Radical copolymerization of methyl methacrylate (MMA) and styrene was performed in [Tb(1,3,5-benzenetrisbenzoate)]n with coordinatively unsaturated metal sites (UMS) immobilized along the one-dimensional nanochannels. A drastic increase in the proportion of MMA units in the resulting copolymers was obtained compared with that obtained from the corresponding solution polymerization systems. Simultaneous coordination of MMA to the UMS is the key to increasing the MMA proportion during the copolymerization in the nanochannels, which was demonstrated by variable temperature IR measurements and several controlled experiments.
TL;DR: Radical polymerization of unpolymerizable sterically hindered butadiene was successfully performed in the nanochannels of porous coordination polymers because of the effective suppression of unfavourable termination reactions.
TL;DR: In this paper, the pore sizes of the porous coordination polymers were tuned systematically according to the dimensionality of inorganic building blocks and the metal-oxygen-metal connectivity of the PCP frameworks.
Abstract: We have developed porous carbons with various pore sizes from porous coordination polymers (PCPs) with Mg2+ and benzene carboxylate linkers The pore sizes of the porous carbons were tuned systematically according to the dimensionality of inorganic building blocks and the metal–oxygen–metal connectivity of the PCP frameworks
TL;DR: A crystalline protein assembly of cypovirus polyhedra was engineered to develop a carbon monoxide releasing extracellular scaffold by immobilizing ruthenium carbonyls.
Abstract: A crystalline protein assembly of cypovirus polyhedra was engineered to develop a carbon monoxide (CO) releasing extracellular scaffold by immobilizing ruthenium carbonyls. The molecular design inc...
TL;DR: A simple strategy of vertex connection that can be used for framework design and pore size/type modulation to prepare a mother structure and another 10 highly porous isoreticular frameworks with unprecedented topology is proposed and validated.
Abstract: We propose and validate a simple strategy of vertex connection that can be used for framework design and pore size/type modulation to prepare a mother structure and another 10 highly porous isoreticular frameworks with unprecedented topology. Importantly, the potential accessible pore volumes (57-71%), pore sizes (6.8-11. 2 A; 17.0-29.0 A; 12.5-22.8 A; 11.9-24.5 A), and the pore shapes of this series of highly porous frameworks were simultaneously and systematically tuned. Interestingly, the pore size of IIa [Zn4O(L(2))2(BDC)0.5]{(CH3)2NH2} decreased a little less than that of IIc [Zn4O(L(2))2(2,6-NDC)0.5]{(CH3)2NH2}; however, its selectivity of CO2 toward CH4 increased by almost two times.
TL;DR: In this paper, the double-perovskite type BaYMn2O5+δ was studied by high-temperature synchrotron X-ray diffraction (SXRD) under precisely controlled oxygen pressure to gain deeper understanding of the remarkable oxygen intake/release capability of this oxide.
Abstract: Crystal structure of double-perovskite type BaYMn2O5+δ was studied by high-temperature synchrotron X-ray diffraction (SXRD) under precisely controlled oxygen pressure to gain deeper understanding of the remarkable oxygen intake/release capability of this oxide. The in situ SXRD analysis at 750 °C revealed that this oxide undergoes a distinct structural change upon lowering oxygen pressure, from a slightly oxygen-deficient “δ = 1” phase (BaYMn2O5.89; P(O2) = 103 Pa) to an oxygen-vacancy ordered “δ = 0.5” phase (BaYMn2O5.51; P(O2) = 10 Pa). The BaYMn2O5.89 structure (orthorhombic Cmmm) involves statistical distribution of oxygen vacancies within the yttrium plane. Meanwhile, the BaYMn2O5.51 structure (orthorhombic Icma) contains arrays of pyramidal MnO5 and octahedral MnO6 forming an alternate ordering, which is stabilized by a particular Mn3+ orbital ordering with collective displacements of Y3+ arrays. Thus, the discontinuous change in the oxygen content can be attributed to the structural reconstruction ...
TL;DR: Two new porous coordination polymers (PCPs), [Cu6(L)4·(H2O)6]·10DMA·4EtOH, (1) and [Cu5 (L)2 (OH)2·( H2O))2·DMA2]·2DMA ·EtO·2H2H 2O (2) were solvothermally synthesized and structurally characterized as mentioned in this paper.
Abstract: Two new porous coordination polymers (PCPs), ([Cu6(L)4·(H2O)6]·10DMA·4EtOH, (1) and [Cu5(L)2 (OH)2·(H2O)2·DMA2]·2DMA·EtOH·2H2O (2), were solvothermally synthesized and structurally characterized. Interestingly, their variable architectures controlled by solvent system exhibit a structural progression from an unusual non-crystallographic (NC) net to a (4,6)-connected framework with fsh topology. Moreover, the combination of 3D channels of about 3.0 × 7.2, 4.7 × 9.5, and 6.3 × 7.8 A2, and functional –OH groups in 2′ lead to good selectivity of CO2 over CH4 (26-55 by IAST) at 273 K.
TL;DR: A flexible and hydrophobic CuII PCP that is stable towards water has been designed and synthesised and has extremely high adsorption selectivity for CO2 over CH4 , derived from its structural flexibility.
Abstract: Invited for this month's cover is the group of Prof. Shin-ichiro Noro from Hokkaido University, Japan. The cover picture shows a copper(II) porous coordination polymer that can adsorb CO2 over CH4 at high selectivity under CO2 /CH4 mixed gas conditions, even with the coexistence of water. Read the full text of the article at 10.1002/cplu.201500278.
TL;DR: Among several substituents investigated, the nitro group has been shown to be the key to obtain the unique foam-like microstructure, which is due to the fast kinetics of gas evolution during carbonization.
Abstract: Porous carbon material with a foam-like microstructure has been synthesized by direct carbonization of porous coordination polymer (PCP). In situ generation of foaming agents by chemical reactions of ligands in PCP during carbonization provides a simple way to create lightweight carbon material with a foam-like microstructure. Among several substituents investigated, the nitro group has been shown to be the key to obtain the unique foam-like microstructure, which is due to the fast kinetics of gas evolution during carbonization. Foam-like microstructural carbon materials showed higher pore volume and specific capacitance compared to a microporous carbon.