6 research outputs found
Crystalline to Crystalline Phase Transformations in Six Two-Dimensional Dynamic Metal–Organic Frameworks: Syntheses, Characterizations, and Sorption Studies
Six dynamic metal–organic
frameworks, namely, {[CdÂ(1,4-bib)Â(glut)]·(4H<sub>2</sub>O)}<sub><i>n</i></sub> (<b>1</b>), {[ZnÂ(1,4-bib)Â(glut)]·(4H<sub>2</sub>O)}<sub><i>n</i></sub> (<b>2</b>), {[CoÂ(1,4-bib)Â(3,5-pydc)]·(2H<sub>2</sub>O)}<sub><i>n</i></sub> (<b>3</b>), {[MnÂ(1,4-bib)Â(3,5-pydc)]·(2H<sub>2</sub>O)}<sub><i>n</i></sub> (<b>4</b>), {[ZnÂ(1,4-bib)Â(3-mglut)]·(4H<sub>2</sub>O)}<sub><i>n</i></sub> (<b>5</b>), and {[ZnÂ(1,4-bib)Â(2,2′-dmglut)]·(2H<sub>2</sub>O)}<sub><i>n</i></sub> (<b>6</b>) from 1-(4-(1<i>H</i>-imidazole-1-yl)Âbutyl)-1<i>H</i>-imidazole (1,4-bib)
using four different dicarboxylic acids salt [disodium glutarate (Na<sub>2</sub>glut), pyridine-3,5-dicarboxylate (3,5-pydc), 3-methyl glutarate
(3-mglut), 2,2′-dimethyl glutarate (Na<sub>2</sub>2,2′-dmglut)],
and four different divalent transition metal ions have been synthesized.
Out of these, the structure of compound <b>3</b> has been previously
reported although synthesized in different method, whereas the rest
of the compounds are new. All of these synthesized compounds are characterized
by single crystal and powder X-ray diffraction and other physicochemical
methods. All the compounds exhibit 2D structure as evident by single
crystal X-ray studies. Interestingly, all of these compounds show
crystalline to crystalline phase transformation. Variable temperature
PXRD study indicates compounds <b>1</b> and <b>6</b> show
single-step phase transformation and the rest show two-step phase
transformation upon desolvation. All of these transformations have
also been established by IR spectroscopy. Among the structural transformations
listed, <b>1</b>–<b>5</b> show reversible crystalline
to crystalline phase transformation on desolvation and resolvation,
whereas <b>6</b> shows an irreversible transformation. All of
these transformations are thoroughly investigated by PXRD and IR spectroscopy.
Sorption studies with CO<sub>2</sub> and N<sub>2</sub> were also performed
for all the metal–organic frameworks and characteristic surface
adsorptions are found in all the cases
Azo Functionalized 5‑Nitro-1,3-benzenedicarboxylate Based Coordination Polymers with Different Dimensionality and Functionality
Five azo-functionalized coordination
polymers (CPs), namely, [ZnÂ(azbpy)Â(NO<sub>2</sub>-bdc)·H<sub>2</sub>O]<sub><i>n</i></sub> (<b>1</b>), [ZnÂ(azbpy)Â(NO<sub>2</sub>-bdc)]<sub><i>n</i></sub>·3H<sub>2</sub>O (<b>2</b>), {[CdÂ(azbpy)Â(NO<sub>2</sub>-bdc)·H<sub>2</sub>O]·2H<sub>2</sub>O}<sub><i>n</i></sub> (<b>3</b>), {[MnÂ(azbpy)<sub>2</sub>Â(NO<sub>2</sub>-bdc)]<sub>2</sub>}<sub><i>n</i></sub> (<b>4</b>), and {[CoÂ(azbpy)Â(NO<sub>2</sub>-bdc)Â(H<sub>2</sub>O)<sub>2</sub>]Â[CoÂ(azbpy)<sub>0.5</sub>Â(NO<sub>2</sub>-bdc)Â(H<sub>2</sub>O)<sub>3</sub>]}<sub><i>n</i></sub> (<b>5</b>) have been synthesized
using different transition
metal salts with 5-nitro-1,3-benzenedicarboxylate (NO<sub>2</sub>-bdc<sup>2–</sup>) and 4,4′-azobispyridine (azbpy) ligand using
a slow diffusion technique at room temperature. The complexes <b>1</b>–<b>5</b> were characterized by single crystal
X-ray diffraction analysis, elemental analysis, infrared spectroscopy
(IR), powder X-ray diffraction (PXRD), and thermogravimetric analysis
(TGA). In the solid state, compound <b>1</b> shows a wavy one-dimensional
(1D) ladder; constructed through the N,N′-donor azbpy and NO<sub>2</sub>-bdc<sup>2–</sup> ligands with the metal centers, whereas
compound <b>2</b> exhibits a bilayer two-dimensional (2D) sheet
containing a wavy 1D ladder of metal-carboxylate, and compound <b>3</b> shows a stairlike wavy 2D sheet. Compound <b>4</b> exhibits a novel 2-fold interdigitated 2D sheet of two similar layers
containing pendent azbpy ligands, whereas compound <b>5</b> displays
a polythreaded 2D structure with an intercalated 1D chain into the
pore. The solid state luminescence properties of <b>1</b>–<b>3</b> along with free N,N′-donor azbpy ligand have been
performed at room temperature, where all the complexes <b>1</b>–<b>3</b> show azbpy ligand based luminescence property.
The gas and solvent vapor adsorption study have been performed for
compounds <b>2</b>–<b>4</b>, and the dehydrated
frameworks of compounds <b>2</b>–<b>4</b> exhibit
selective CO<sub>2</sub> adsorption at 195 K over N<sub>2</sub> (at
both 77 and 195 K) due to the strong interactions between polar pore
walls of dehydrated frameworks with the CO<sub>2</sub> molecule having
quadruple moment
Reversible Phase Transformation in Three Dynamic Mixed-Ligand Metal–Organic Frameworks: Synthesis, Structure, and Sorption Study
Three new dynamic metal–organic
frameworks (MOFs) namely
{[Cd<sub>2</sub>(3,4-pyrdc)<sub>2</sub>(4,4′-bipy)Â(H<sub>2</sub>O)<sub>2</sub>]·4H<sub>2</sub>O}<sub><i>n</i></sub> (<b>1</b>), {[Mn<sub>2</sub>(3,4-pyrdc)<sub>2</sub>(bpee)Â(H<sub>2</sub>O)<sub>2</sub>]·H<sub>2</sub>O}<sub><i>n</i></sub> (<b>2</b>), and {[Cu<sub>2</sub>(3,4- pyrdc)<sub>2</sub>(bpp)<sub>2</sub>(H<sub>2</sub>O)<sub>4</sub>]·5H<sub>2</sub>O}<sub><i>n</i></sub> (<b>3</b>), based on 3,4-pyridinedicarboxylate
(3,4-pyrdc) and three different N,N′-donor ligands [4,4′-bipyridine
(4,4′-bipy), 1,2-bisÂ(4-pyridyl)Âethylene (bpee), and 1,3-bisÂ(4-pyridyl)-propane
(bpp)] with various divalent transition metal ions have been synthesized
and characterized by single-crystal and powder X-ray diffraction and
other physicochemical methods. In compounds <b>1</b> and <b>2</b>, the 3,4-pyrdc ligand forms two-dimensional (2D) metal–carboxylate
sheets that are connected by N,N′-donor ligands to form three-dimensional
(3D) structures with water-filled channels. In compound <b>3</b>, the 3,4-pyrdc ligand affords one-dimensional metal–carboxylate
chains. These chains are connected by the more flexible bpp ligand
to form 2D structures, which are extended to a 3D supramolecular architecture
by H-bonding. Compounds <b>1</b> and <b>2</b> show a reversible
crystalline-to-crystalline phase transformation upon dehydration and
rehydration, whereas compound <b>3</b> exhibits an interesting
reversible crystalline-to-amorphous transformation. These transformations
have been established and monitored by exhaustive X-ray powder diffraction,
elemental analysis, IR spectroscopy, thermogravimetric analysis, and
morphology studies. The dehydrated forms of <b>1</b>–<b>3</b> selectively adsorb CO<sub>2</sub> over N<sub>2</sub> and
also exhibit stepwise water uptake
Selective CO<sub>2</sub> Adsorption by Nitro Functionalized Metal Organic Frameworks
Two
nitro functionalized CuÂ(II)-MOFs exhibit high CO<sub>2</sub> uptake
with nice selectivity over other gases like H<sub>2</sub>, N<sub>2</sub>, and CH<sub>4</sub>, which is potentially important
for the removal of carbon dioxide from industrial flue gas and natural
gas. Here the selective CO<sub>2</sub> adsorption by these MOFs is
primarily due to the presence of suitable voids with −NO<sub>2</sub> group functionalized pore walls in the dehydrated framework,
which is unprecedented
Hydrogen Uptake by an Inclined Polycatenated Dynamic Metal–Organic Framework Based Material
A 2D + 2D → 3D inclined polycatenated
dynamic metal–organic
framework of {[CuÂ(4-bpe)Â(2-ntp)Â(H<sub>2</sub>O)<sub>2</sub>]·2H<sub>2</sub>O}<sub><i>n</i></sub> [<b>1</b>, where 2-ntp<sup>2–</sup> = 2-nitroterephthalate and 4-bpe = 1,2-bis-(4-pyridyl)Âethane]
has been synthesized and characterized. The variable-temperature powder
X-ray diffraction study indicates the dynamic nature of the inclined
polycatenated framework, and the dehydrated framework with exposed
metal centers exhibits excellent type I H<sub>2</sub> adsorption of
1.94 wt % at 77 K and 1 bar of pressure
Set of Multifunctional Azo Functionalized Semiconducting Cd(II)-MOFs Showing Photoswitching Property and Selective CO<sub>2</sub> Adsorption
Syntheses,
structural characterizations, photoluminescence, and adsorption properties
of three new azo-functionalized CdÂ(II)-MOFs, namely, {[CdÂ(azbpy)Â(msuc)]·2.5Â(H<sub>2</sub>O)}<sub><i>n</i></sub> (<b>2</b>), {[CdÂ(azbpy)Â(mglu)]·5Â(H<sub>2</sub>O)}<sub><i>n</i></sub> (<b>3</b>), and {[Cd<sub>1.5</sub>(azbpy)<sub>2</sub>(glu)]·(NO<sub>3</sub>)·MeOH}<sub><i>n</i></sub> (<b>4</b>) [where msuc<sup>2−</sup> = methylsuccinate; mglut<sup>2−</sup> = methylglutarate;
glut<sup>2−</sup> = glutarate; azbpy = 4,4′-azobispyridine]
have been reported. The compounds show different structures only with
the variation of aliphatic dicarboxylates. The photoswitching behavior
for the above-mentioned newly synthesized CdÂ(II)-MOFs along with one
of our previously reported other azo-functionalized CdÂ(II)-MOF, namely,
{[CdÂ(azbpy)Â(suc)]·2Â(H<sub>2</sub>O)}<sub><i>n</i></sub> (<b>1</b>), has been studied extensively. At photoilluminated
condition, the conductivity values can draw a clear structure–property
relationship among the structures of compounds <b>1</b>–<b>4</b>. Single crystal structural analysis reveals that all the
compounds exhibit a three-dimensional (3D) framework connected by
azbpy linker and respective aliphatic dicarboxylate through their
bis-chelating mono/bis oxo-bridging fashion. Compounds <b>1</b>–<b>3</b> exhibit an iso-structural honeycomb like 3D
framework showing the same coordination environments, where the metal-carboxylate
2D sheets of compounds <b>1</b>–<b>3</b> are pillared
by N,N′-donor azbpy linkers. On the other hand, compound <b>4</b> exhibits a 2-fold interpenetrated 3D framework with a little
difference in its coordination environment and the pillaring of 1D
metal-carboxylate ladder by azbpy linkers. All the compounds significantly
demonstrate their enhanced sensitivity under light rather than the
dark condition. The gas and solvent vapor sorption studies have been
performed for the synthesized compounds <b>2</b>–<b>4</b>. Moreover, compound <b>2</b> exhibits an enhanced
type IV selective CO<sub>2</sub> adsorption isotherm over N<sub>2</sub> along with the appearance of gate opening phenomena in that