Won Cho

Self-Template-Directed Formation of Coordination-Polymer Hexagonal Tubes and Rings, and their Calcination to ZnO Rings†

This template will self-destruct: A unique particle-growth mechanism involves growth of new coordination polymers on the surface of initially formed hexagonal blocks and concomitant dissolution of the blocks to form hexagonal tubes (see scheme and scanning electron, optical, and fluorescence microscopy images). Calcination of the tubes yields ZnO particles of the same shape.

Growth-Controlled Formation of Porous Coordination Polymer Particles

Diversely shaped porous coordination polymer particles (CPPs) were synthesized by a simple solvothermal reaction of 1,4-benzenedicarboxylic acid (H2BDC) and In(NO3)3 x xH2O in DMF. The growth of crystalline CPPs was controlled through a particle growth blocking event involving blocking agent interaction with particular facets of CPPs and simultaneous particle growth interruption in a specific direction. Systematic reactions in the presence of various amounts of pyridine as a blocking agent were conducted to see the controlled CPP formation. Long rod, short rod, lump, and disk-shaped CPPs with hexagonal faces resulted in the presence of none, 1 equiv, 2 equiv, and 25 equiv of pyridine, respectively. The ultimate particle shape produced depends upon the amount of blocking agents used.

Coordination polymer nanorods of Fe-MIL-88B and their utilization for selective preparation of hematite and magnetite nanorods

Coordination polymer nanorods are synthesized from the hexagonal 3D structure of Fe-MIL-88B. Subsequently, hematite (α-Fe(2)O(3)) and magnetite (Fe(3)O(4)) nanorods are selectively prepared by controlling the calcination conditions of coordination polymer nanorods.

Multi Ball‐In‐Ball Hybrid Metal Oxides

Scheme 1 . Preparation of multi ball-in-ball hybrid metal oxides. Many examples of microand nanoscale particles made from atomic or molecular building blocks are known, with these systems having been extensively explored due to their useful properties. [ 1–6 ] Currently, efforts are ongoing to manipulate the composition, as well as its size and morphology, of particles as part of systematic attempts to alter their chemical and physical properties. Within this context, chemical transformation has emerged a useful method for tuning the composition. [ 7 , 8 ]

One-pot synthesis of magnetic particle-embedded porous carbon composites from metal-organic frameworks and their sorption properties.

Nano- and micro-composites comprised of porous carbon and magnetic particles are prepared by one-step pyrolysis of metal-organic frameworks (MOFs). The porosity and composition of resulting magnetic porous carbons are facilely regulated by altering the pyrolysis temperature and changing the organic building blocks incorporated within the initial MOFs.

Dual Changes in Conformation and Optical Properties of Fluorophores within a Metal–Organic Framework during Framework Construction and Associated Sensing Event

Microsized chemosensor particle (CPP-16, CPP means coordination polymer particle), which is made from a metal-organic framework (MOF), is synthesized using pyrene-functionalized organic building block. This building block contains three important parts, a framework construction part, a Cu(2+) detection part, and a fluorophore part. PXRD studies have revealed that CPP-16 has a 3D cubic structure of MOF-5. During both MOF formation and sensing event, fluorophores within CPP-16 undergo dual changes in conformation and optical properties. After MOF construction, pyrene moieties experience an unusual complete conversion from monomer to excimer form. This conversion takes place due to a confinement effect induced by space limitations within the MOF structure. The selective sensing ability of CPP-16 on Cu(2+) over many other metal ions is verified by emission spectra and is also visually identified by fluorescence microscopy images. Specific interaction of Cu(2+) with binding sites within CPP-16 causes a second conformational change of the fluorophores, where they change from stacked excimer (CPP-16) to quenched excimer states (CPP-16·Cu(2+)).

Facile Synthetic Route for Thickness and Composition Tunable Hollow Metal Oxide Spheres from Silica‐Templated Coordination Polymers

chemical sensors, [ 2 ] photonic devices, [ 3 ] energy storage, [ 4 ] chemical reactors, [ 5 ] and drug delivery. [ 6 ] Several methods, including template-free methods [ 7 ] and templating methods using either hard or soft templates, [ 8 ] have been developed to fabricate hollow structures. Templating methods often yield products with narrow size distributions and clear-cut structural features. In addition, the size of hollow products prepared using templating methods can be controlled easily by varying the size of the templates used in the reactions. However, there are inherent drawbacks involved in immobilizing desired materials on template surfaces due to potential incompatibilities between materials. On the other hand, coordination polymer materials, including macroscaled crystalline products [ 9 ] and nanoor microsized coordination polymer particles (CPPs), [ 10 ] have attracted much attention because of their unique applications in gas storage, catalysis, separation, and optics. The merger of coordination poly mers with other solid materials is expected to expand the scope of their utilization. [ 11 , 12 ] Recently, we developed a coordination-induced approach to immobilize coordination polymers consisting of In 3 + and isophthalic acid (H 2 IPA) building blocks onto carboxylatefunctionalized silica beads to derive the formation of silica@ coordination polymer core/shell structures, in which the thickness of the resulting coordination polymer shells was easily controlled by altering the quantities of shell components. [ 12 ] Herein, we report a novel general method for the preparation of hollow metal oxides using various metals. We demonstrate that considerably monodisperse hollow metal oxides can be produced from silica@coordination polymer core/shell precursors through a calcination process that transforms coordination polymers into metal oxides, followed by an etching process to remove silica templates ( Scheme 1 ). In addition, we show that the layer thicknesses of the hollow structures can be controlled by adjusting the shell thicknesses of the coordination polymers within the silica@ coordination polymer core/shell precursors. First, silica@coordination polymer core/shell microspheres were prepared using a solvothermal method. A N,N -dimethylformamide (DMF) solution of coordination

Controlled isotropic or anisotropic nanoscale growth of coordination polymers: formation of hybrid coordination polymer particles.

The ability to fabricate multicompositional hybrid materials in a precise and controlled manner is one of the primary goals of modern materials science research. In addition, an understanding of the phenomena associated with the systematic growth of one material on another can facilitate the evolution of multifunctional hybrid materials. Here, we demonstrate precise manipulation of the isotropic and/or anisotropic nanoscale growth of various coordination polymers (CPs) to obtain heterocompositional hybrid coordination polymer particles. Chemical composition analyses conducted at every growth step reveal the formation of accurately assembled hybrid nanoscale CPs, and microscopy images are used to examine the morphology of the particles and visualize the hybrid structures. The dissimilar growth behavior, that is, growth in an isotropic or anisotropic fashion, is found to be dependent on the size of the metal ions involved within the CPs.

Fluorescent octahedron and rounded-octahedron coordination polymer particles (CPPs)

Narrowly-dispersed fluorescent octahedron and rounded-octahedron coordination polymer particles (CPPs) have been synthesized from the solvothermal reaction of In(NO3)3·xH2O and 2,6-bis[(4-carboxyanilino)carbonyl]pyridine. The shape and size of the resulting CPPs were dependent on the amount of solvent (and thus the concentration of reactants) used in the reaction. Under poor solubility conditions with only a small amount of DMF, the formation of coordination polymers proceeds quickly and the particle growth commences at a large number of sites, thus resulting in smaller particles. By decreasing the amount of DMF used in the reaction from 800 μL to 400 and 200 μL, the average size of the resulting CPPs was reduced from 2.22 ± 0.40 μm to 834 ± 120 and 431 ± 36.9 nm, respectively. In addition, we have found that some additives such as bipyridine and acetic acid, even though they were not incorporated within CPPs, did play an important role in the formation of CPPs by means of manipulating the deprotonation rate of organic building blocks and so affect the size and morphology of the resulting CPPs. Fluorescent octahedron and rounded-octahedron CPPs with specific size ranging from 307 nm to 2.22 μm were successfully prepared. Control of the size and morphology of colloidal particles is one of our central aims, both in terms of fundamental interest and for practical applications. Therefore, this work should provide significant assistance in the development of CPP materials.

Highly effective heterogeneous chemosensors of luminescent silica@coordination polymer core-shell micro-structures for metal ion sensing

Heterogeneous solid sensors are regarded as promising next-generation sensor due to their excellent chemical stability, low contamination, and excellent recyclability, despite their low sensitivity and weak signal. The dispersity and signals specifically from the exterior of solid sensors are critical aspects which define the sensing sensitivity and selectivity. A novel strategy for the preparation of ideal heterogeneous sensors based upon luminescent lanthanide coordination polymers (LnCP) has been demonstrated. Ideal heterogeneous sensors are systematically achieved by producing the sensors in small, uniform, and thin core-shell particles (silica@LnCP, Ln = Eu, Tb). Eventually, we found that the extremely small amount of well-structured silica@LnCP microsphere, less than ca. 1/400 compared to the amount of several known coordination polymer-based sensors, was sufficient to achieve a reliable Cu2+ sensing with even much greater sensitivity (ca. 550% improvement).