204 research outputs found
Structuralization of Ca(2+)-based metal-organic frameworks prepared via coordination replication of calcium carbonate
No full textPublished: March 22, 2016The emergence of metal-organic frameworks (MOFs) as potential candidates to supplant existing adsorbent types in real-world applications has led to an explosive growth in the number of compounds available to researchers, as well as in the diversity of the metal salts and organic linkers from which they are derived. In this context, the use of carbonate-based precursors as metal sources is of interest due to their abundance in mineral deposits and their reaction chemistry with acids, resulting in just water and carbon dioxide as side products. Here, we have explored the use of calcium carbonate as a metal source and demonstrate its versatility as a precursor to several known frameworks, as well as a new flexible compound based on the 2,5-dihydroxybenzoquinone (H₂dhbq) linker, Ca(dhbq)(H₂O)₂. Furthermore, inspired by the ubiquity and unique structures of biomineralized forms of calcium carbonate, we also present examples of the preparation of superstructures of Ca-based MOFs via the coordination replication technique. In all, the results confirm the suitability of carbonate-based metal sources for the preparation of MOFs and further expand upon the growing scope of coordination replication as a convenient strategy for the preparation of structuralized materials.Kenji Sumida, Ming Hu, Shuhei Furukawa, and Susumu Kitagaw
Impact of molecular clustering inside nanopores on desorption processes
No full textUnderstanding the sorption kinetics of nanoporous systems is crucial for the development and design of novel porous materials for practical applications. Here, using a porous coordination polymer/quartz crystal microbalance (PCP/QCM) hybrid device, we investigate the desorption of various vapor molecules featuring different degrees of intermolecular (hydrogen bonding) or molecule-framework interactions. Our findings reveal that strong intermolecular interactions lead to the desorption process proceeding via an unprecedented metastable state, wherein the guest molecules are clustered within the pores, causing the desorption rate to be temporarily slowed. The results demonstrate the considerable impact of the chemical nature of an adsorbate on the kinetics of desorption, which is also expected to influence the efficiency of certain processes, such as desorption by gas purge.Manuel Tsotsalas, Pavel Hejcik, Kenji Sumida, Ziya Kalay, Shuhei Furukawa, and Susumu Kitagaw
Design of superhydrophobic porous coordination polymers through the introduction of external surface corrugation by the use of an aromatic hydrocarbon building unit
No full textAlso published in Angewandte Chemie, 2014;126(31):8364–8369We demonstrate a new approach to superhydrophobic porous coordination polymers by incorporating an anisotropic crystal morphology featuring a predominant surface that is highly corrugated and terminated by aromatic hydrocarbon moieties. The resulting low-energy surface provides particularly promising hydrophobic properties without the need for postsynthetic modifications or surface processing that would block the porosity of the framework. Consequently, hydrophobic organic molecules and water vapor are able to penetrate the surface and be densely accommodated within the pores, whereas bulk water is repelled as a result of the exterior surface corrugation derived from the aromatic surface groups. This study provides a new strategy for the design and development of superhydrophobic porous materials.Koya Prabhakara Rao, Masakazu Higuchi, Kenji Sumida, Shuhei Furukawa, Jingui Duan, and Susumu Kitagaw
Emerging applications of metal-organic frameworks
No full textMetal–organic frameworks are a unique class of materials well known for their crystallinity and ultra-high porosity. Since their first report over fifteen years ago, research in this area has sought to actively exploit these properties, especially in gas adsorption. In this article we canvass some emerging topics in the field of MOF research that show promise for new applications in areas such as biotechnology, catalysis, and microelectronics.Raffaele Ricco, Constance Pfeiffer, Kenji Sumida, Christopher J. Sumby, Paolo Falcaro, Shuhei Furukawa, Neil R. Champness and Christian J. Doona
Dynamic properties of a flexible metal-organic framework exhibiting a unique “picture frame”-like crystal morphology
No full textPublished: 15 August 2020The precise control of the crystal morphology of metal-organic frameworks (MOFs) enables optimization of its adsorptive properties, as well as enables better integration within functional devices. However, the influence of such modifications on the dynamic properties of flexible MOFs is poorly understood. Here, we report the synthesis of a series of Cu2(bdc)2(bpy) (bdc2− = 1,4-benzenedicarboxylate; bpy = 4,4′-bipyridine) crystals having an unusual picture frame-like morphology that results from a restriction in the quantity of bpy pillars added to the reaction mixture during the intercalation of the Cu2(bdc)2(MeOH)2 layers. The width of the frames is found to correlate with the quantity of bpy, and importantly, causes the dynamic properties of the resulting Cu2(bdc)2(bpy) material to vary between rigid, elastic, and shape memory modes. In all, the results demonstrate the potential for the properties of MOFs to be optimized via subtle manipulations in the crystal morphology rather than changes in the overall material composition.Kenji Sumida, Nao Horike and Shuhei Furukaw
Sol-gel processing of metal-organic frameworks
No full textSol-gel processing represents a powerful and versatile strategy for the preparation of functional inorganic and hybrid materials that facilitate control over the molecular composition, as well as organization of the materials at the various length scales relevant to fundamental and applied research. Recent advances have enabled its use for the processing of an emerging class of functional porous materials called metal–organic frameworks (MOFs). Here, sol–gel approaches can be employed for the direct manipulation of MOFs, or as a route to the construction of composite materials where the properties of the MOF are synergistically combined with those of a carefully chosen inorganic phase. In this review, we present the most significant progress made in this emerging area, according to four main synthetic strategies, with a particular focus on describing how sol–gel processing enhances the functionalities of the MOF. These strategies include (1) molecular scale manipulations of the pore surfaces of MOFs with sol–gel precursors; (2) the controlled positioning or growth of MOF crystals on inorganic surfaces; (3) the use of MOF crystals as templates for sol–gel processes (either within the pores, or at the external surfaces); and (4) the use of sol–gel-derived sacrificial inorganic templates for the structuring of MOF-based architectures. Each of these processing methods imparts unique properties to the systems and provides a route to higher-order architectures and material compositions not accessible through conventional approaches to MOF synthesis. Sol–gel processing provides promising routes toward new functional materials that display enhanced properties and are expected to play an important role in allowing MOFs to be optimized for specific applications.Kenji Sumida, Kang Liang, Julien Reboul, Ilich A. Ibarra, Shuhei Furukawa and Paolo Falcar
Impact of crystal orientation on the adsorption kinetics of a porous coordination polymer-quartz crystal microbalance hybrid sensor
No full textThe hybridization of porous coordination polymers (PCPs) with electronic devices is a powerful strategy for developing systems that are suitable for advanced applications, such as chemical sensing. The quartz crystal microbalance (QCM) technique is one that allows minute mass changes to be resolved with a high temporal resolution, and the growth of PCP crystals that provide selective adsorption properties on a QCM substrate can facilitate the rapid detection of certain molecules from a gas or vapour mixture. Herein, we demonstrate the immobilization of the flexible PCP Zn(NO₂-ip)(bpy) (Zn-CID-5; NO₂-ip²⁻ = 5-nitroisophthalate, bpy = 4,4′-bipyridine) on QCM substrates and investigate the adsorptive properties of the fabricated systems. Notably, the crystal orientation could be controlled by the anchoring of chemical functionalities on the substrate surface, or by the addition of coordination modulators (e.g. 4-phenylpyridine) at the time of growth of the PCP crystals on the substrates. Here, the crystal orientation plays a significant role in determining the detection kinetics of organic vapours (e.g. methanol), and the [010]-oriented case which displays the fastest adsorption kinetics among the samples tested is studied under mixed component (methanol–hexane) conditions to demonstrate its response profile. In all, the results demonstrate the potential utility of PCP/QCM hybrid systems in sensor applications, and also serve to highlight the importance of optimizing the physical orientation of crystal growth in such systems to maximize the overall performance of the system.Kenji Hirai, Kenji Sumida, Mikhail Meilikhov, Nicolas Louvain, Masashi Nakahama, Hiromitsu Uehara, Susumu Kitagawa and Shuhei Furukaw
Particle size effects in the kinetic trapping of a structurally-locked form of a flexible metal-organic framework
No full textFirst published online 08 Feb 2016The application of metal-org. frameworks (MOFs) for gas storage, mol. sepns. and catalysis neccesitates careful consideration of the particle size and structuralisation (e.g. pelletisation, surface-anchoring) of a material. Recently, particle size has been shown to dramatically alter the phys. and structural properties of certain MOFs but overall there is limited information on how the particle size affects the properties of flexible MOFs. Here we demonstrate that the particle size of a flexible MOF, specifically the as-synthesized form of [Cu(bcppm)H2O]•S (H2bcppm = bis(4-(4-carboxyphenyl)-1H-pyrazolyl)methane, S = solvent) (1), correlates with the rate of structural reorganisation from a "kinetically-trapped" activated 3D form of this MOF to the "open" 2D form of the structure. We also outline two methods for synthetically reducing the particle size of 1 at room temp., using 0.1 M NaOH (for two reaction times: 0.5 and 16 h) and with the sodium salt of the ligand Na2bcppm, producing crystals of 85 ± 15, 280 ± 14 and 402 ± 41 nm, resp. [on SciFinder(R)]Oliver M. Linder-Patton, Witold M. Bloch, Campbell J. Coghlan, Kenji Sumida, Susumu Kitagawa, Shuhei Furukawa, Christian J. Doonan and Christopher J. Sumb
Effects of rewarming therapies on outcomes in accidental hypothermia: A secondary analysis of a multicenter prospective study
No full text弘前大学博士（医学）Author(s): Kana Sugiyama, Osamu Nomura, Jin Irie, Yoshiya Ishizawa, Shuhei Takauji, Mineji Hayakawa, Yoshinori Tamada, Hiroyuki Hanad
Construction and analysis of guiding center distributions for tokamak plasmas with ambient radial electric field
No full textThe contribution of a time-independent toroidally-symmetric radial electric field Er is implemented in VisualStart (Bierwage et al. (2022) [21]), a code whose purposes include the construction of guiding center (GC) drift orbit databases for the study of plasma instabilities in tokamaks. Er alters the transit frequencies and orbit shapes of charged particles, and it shifts the trapped-passing boundary, especially in the thermal part of the velocity distribution. Er can also affect fast particle resonances in the kHz frequency range. Here, KSTAR, JT-60U and ITER tokamak cases are used as working examples to test our methods. In the course of our detailed consistency checks, we unravel how nonuniformities in the moments of a GC distribution emerge from the collection of individual GC orbits. We also discuss technical and practical issues connected with Er, two of which shall be emphasized here: First, the GC orbit space is sampled in the magnetic midplane as before, and we find that, in the presence of Er, midplane-based coordinates are not only equivalent but superior to conventional constants of motion, allowing to attain high numerical accuracy and efficiency with a relatively simple mesh. Second, the periodic parallel acceleration and deceleration of GCs via the mirror force is modulated by Er. Although its poloidal transit (bounce) average is zero, this parallel electric acceleration gives rise to a reference point bias: When measured at fixed GC launch coordinates, the toroidal transit frequency of passing orbits acquires an apparent Er-dependence, which can cause confusion.
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