35 research outputs found
High Proton Conductivity of Zinc Oxalate Coordination Polymers Mediated by a Hydrogen Bond with Pyridinium
A novel metalâorganic framework,
(Hpy)<sub>2</sub>[Zn<sub>2</sub>(ox)<sub>3</sub>]·<i>n</i>H<sub>2</sub>O (<i>n</i> = 0, 1), having a pyridinium cation,
was newly synthesized, and the crystal structures were determined.
The hydrated compound shows a high proton conductivity of 2.2 Ă
10<sup>â3</sup> S cm<sup>â1</sup> at 298 K and 98% relative
humidity. Single crystal XRD analysis revealed a rotational displacement
factor for the hydrated pyridinium ring and elongated water site that
is thought to cause the high proton conductivity
High Proton Conductivity of Zinc Oxalate Coordination Polymers Mediated by a Hydrogen Bond with Pyridinium
A novel metalâorganic framework,
(Hpy)<sub>2</sub>[Zn<sub>2</sub>(ox)<sub>3</sub>]·<i>n</i>H<sub>2</sub>O (<i>n</i> = 0, 1), having a pyridinium cation,
was newly synthesized, and the crystal structures were determined.
The hydrated compound shows a high proton conductivity of 2.2 Ă
10<sup>â3</sup> S cm<sup>â1</sup> at 298 K and 98% relative
humidity. Single crystal XRD analysis revealed a rotational displacement
factor for the hydrated pyridinium ring and elongated water site that
is thought to cause the high proton conductivity
High Proton Conductivity of Zinc Oxalate Coordination Polymers Mediated by a Hydrogen Bond with Pyridinium
A novel metalâorganic framework,
(Hpy)<sub>2</sub>[Zn<sub>2</sub>(ox)<sub>3</sub>]·<i>n</i>H<sub>2</sub>O (<i>n</i> = 0, 1), having a pyridinium cation,
was newly synthesized, and the crystal structures were determined.
The hydrated compound shows a high proton conductivity of 2.2 Ă
10<sup>â3</sup> S cm<sup>â1</sup> at 298 K and 98% relative
humidity. Single crystal XRD analysis revealed a rotational displacement
factor for the hydrated pyridinium ring and elongated water site that
is thought to cause the high proton conductivity
Supramolecular Thermo-Electrochemical Cells: Enhanced Thermoelectric Performance by HostâGuest Complexation and Salt-Induced Crystallization
Thermo-electrochemical
cells have potential to generate thermoelectric
voltage 1 order higher than that given by semiconductor materials.
To overcome the current issues in thermoelectric energy conversion,
it is of paramount importance to grow and fulfill the full potential
of thermo-electrochemical cells. Here we report a rational supramolecular
methodology that yielded the highest Seebeck coefficient of ca. 2.0
mV K<sup>â1</sup> around ambient temperatures. This is based
on the encapsulation of triiodide ions in α-cyclodextrin, whose
equilibrium is shifted to the complexation at lower temperatures,
whereas it is inverted at elevated temperatures. This temperature-dependent
hostâguest interaction provides a concentration gradient of
redox ion pairs between two electrodes, leading to the eminent performance
of the thermo-electrochemical cells. The figure of merit for this
system, <i>zT</i> reached a high value of 5 Ă 10<sup>â3</sup>. The introduction of hostâguest chemistry
to thermoelectric cells thus provides a new perspective in thermoelectric
energy conversion
Proton Conductivity Control by Ion Substitution in a Highly Proton-Conductive MetalâOrganic Framework
Proton conductivity through two-dimensional
(2-D) hydrogen-bonding
networks within a layered metalâorganic framework (MOF) (NH<sub>4</sub>)<sub>2</sub>(H<sub>2</sub>adp)Â[Zn<sub>2</sub>(ox)<sub>3</sub>]·3H<sub>2</sub>O (H<sub>2</sub>adp = adipic acid; ox = oxalate)
has been successfully controlled by cation substitution. We synthesized
a cation-substituted MOF, K<sub>2</sub>(H<sub>2</sub>adp)Â[Zn<sub>2</sub>(ox)<sub>3</sub>]·3H<sub>2</sub>O, 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
Selective Separation of Water, Methanol, and Ethanol by a Porous Coordination Polymer Built with a Flexible Tetrahedral Ligand
A novel porous coordination polymer, Cu<sup>II</sup>(mtpm)ÂCl<sub>2</sub> [mtpm = tetrakisÂ(<i>m</i>-pyridyloxy methylene)Âmethane],
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
3D Coordination Polymer of Cd(II) with an Imidazolium-Based Linker Showing Parallel Polycatenation Forming Channels with Aligned Imidazolium Groups
A novel entangled architecture formed
on solvothermal reaction
of a imidazolium based bent ligand with CdÂ(NO<sub>3</sub>)<sub>2</sub>, showing 1D channels decorated with imidazolium groups, is reported.
The polymer, {[Cd<sub>2</sub>(L)<sub>3</sub>(DMF)Â(NO<sub>3</sub>)]Â(DMF)<sub>3</sub>(H<sub>2</sub>O)<sub>8</sub>}<sub><i>n</i></sub> (<b>1</b>) (where H<sub>2</sub>L = 1,3-bisÂ(4-carboxyphenyl)Âimidazolium,
DMF = dimethylformamide), shows an interesting 6,3-connected polycatenated
structure with channels along the crystallographic <i>b</i>-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 Ă 10<sup>â5</sup> Scm<sup>â1</sup> at 25 °C
and 98% RH when water molecules are introduced into the empty channels
Control of Crystalline Proton-Conducting Pathways by Water-Induced Transformations of Hydrogen-Bonding Networks in a MetalâOrganic Framework
Structure-defined
metalâorganic 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 (NH<sub>4</sub>)<sub>2</sub>(adp)Â[Zn<sub>2</sub>(ox)<sub>3</sub>]·<i>n</i>H<sub>2</sub>O (abbreviated to <b>1·</b><i><b>n</b></i><b>H</b><sub><b>2</b></sub><b>O</b>, adp: adipic acid, ox: oxalate, <i>n</i> = 0, 2, 3) having
definite crystal structures and showing reversible structural transformations
among the anhydrate (<b>1</b>), dihydrate (<b>1·2H</b><sub><b>2</b></sub><b>O</b>), and trihydrate (<b>1·3H</b><sub><b>2</b></sub><b>O</b>) 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 <b>1·2H</b><sub><b>2</b></sub><b>O</b> and <b>1·3H</b><sub><b>2</b></sub><b>O</b>. The crystal system of <b>1</b> or <b>1·2H</b><sub><b>2</b></sub><b>O</b> (<i>P</i>2<sub>1</sub>/<i>c</i>, No. 14) was changed into
that of <b>1·3H</b><sub><b>2</b></sub><b>O</b> (<i>P</i>1Ì
, 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 âŒ10<sup>â12</sup> S cm<sup>â1</sup> (<b>1</b>) to âŒ10<sup>â2</sup> S cm<sup>â1</sup> (<b>1·3H</b><sub><b>2</b></sub><b>O</b>) 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
Control of Crystalline Proton-Conducting Pathways by Water-Induced Transformations of Hydrogen-Bonding Networks in a MetalâOrganic Framework
Structure-defined
metalâorganic 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 (NH<sub>4</sub>)<sub>2</sub>(adp)Â[Zn<sub>2</sub>(ox)<sub>3</sub>]·<i>n</i>H<sub>2</sub>O (abbreviated to <b>1·</b><i><b>n</b></i><b>H</b><sub><b>2</b></sub><b>O</b>, adp: adipic acid, ox: oxalate, <i>n</i> = 0, 2, 3) having
definite crystal structures and showing reversible structural transformations
among the anhydrate (<b>1</b>), dihydrate (<b>1·2H</b><sub><b>2</b></sub><b>O</b>), and trihydrate (<b>1·3H</b><sub><b>2</b></sub><b>O</b>) 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 <b>1·2H</b><sub><b>2</b></sub><b>O</b> and <b>1·3H</b><sub><b>2</b></sub><b>O</b>. The crystal system of <b>1</b> or <b>1·2H</b><sub><b>2</b></sub><b>O</b> (<i>P</i>2<sub>1</sub>/<i>c</i>, No. 14) was changed into
that of <b>1·3H</b><sub><b>2</b></sub><b>O</b> (<i>P</i>1Ì
, 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 âŒ10<sup>â12</sup> S cm<sup>â1</sup> (<b>1</b>) to âŒ10<sup>â2</sup> S cm<sup>â1</sup> (<b>1·3H</b><sub><b>2</b></sub><b>O</b>) 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
Facile âModular Assemblyâ for Fast Construction of a Highly Oriented Crystalline MOF Nanofilm
The preparation of crystalline, ordered thin films of
metalâorganic
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,
CuâTCPP [TCPP = 5,10,15,20-tetrakisÂ(4-carboxyphenyl)Âporphyrin],
by a new âmodular assemblyâ strategy. The modular assembly
process involves two steps: a âmodularizationâ step
is used to synthesize highly crystalline âmodulesâ with
a nanosized structure that can be conveniently assembled into a thin
film in the following âassemblyâ 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