scholarly journals Elucidation of the Mechanism of Phase Transition in a Zinc Formate Framework Templated by a Diammonium Cation—Structural, Phonon and Dielectric Studies

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 213
Author(s):  
Aneta Ciupa-Litwa ◽  
Jan Janczak ◽  
Paulina Peksa ◽  
Adam Sieradzki
Keyword(s):  
Phase Transition ◽  
Metal Organic Framework ◽  
Structural Phase ◽  
Synthesis Method ◽  
Spectroscopic Studies ◽  
X Ray Diffraction ◽  
Dipolar Relaxation ◽  
Asymmetric Shape ◽  
Metal Organic ◽  
Anionic Framework

In this paper we present the synthesis method and a detailed description of the crystal structure, as well as thermal, dielectric and phonon properties, of the [CH3NH2CH2CH2NH2CH3][Zn2(HCOO)6] (dmenH2-Zn) metal organic framework. The negative charge of the anionic framework ([Zn2(HCOO)6]2-) is balanced by N,N′-dimethylethylenediamine (dmenH22+) ions located in the voids of the framework. Thermal analysis revealed that dmenH2-Zn underwent a reversible structural phase transition at around room temperature (Tc~300 K). The single-crystal X-ray diffraction showed that dmenH22+ templates were dynamically disordered at 295 K, since N-H…O bonds were too weak to surmount their thermally activated motions. Reduction in the temperature resulted in ordering of the dmenH22+ cations as a consequence of freezing of their reorientational movements. This behavior caused a symmetry change from P-31c (trigonal) to C 2/c (monoclinic). The mechanism of the observed phase transition of dmenH2-Zn compound was also investigated by temperature-dependent IR measurements. These spectroscopic studies showed that the ordering of the dmenH22+ ions also resulted in the distortion of the anionic framework. Dielectric investigations revealed the occurrence of the dipolar relaxation process clearly defined in the monoclinic phase. The asymmetric shape of the studied process, which indicated a non-Debye-like relaxation, was analyzed using the Havriliak–Negami relaxation function, leading to an Ea value of approximately 0.36 eV.

EPR Study of Structural Phase Transition in Manganese-Doped [(CH3)2NH2][Zn(HCOO)3] Metal–Organic Framework

2015 ◽  
Vol 119 (43) ◽  
pp. 24522-24528 ◽  
Author(s):  
Mantas Šimėnas ◽  
Aneta Ciupa ◽  
Mirosław Ma̧czka ◽  
Andreas Pöppl ◽  
Ju̅ras Banys
Keyword(s):  
Phase Transition ◽  
Structural Phase Transition ◽  
Metal Organic Framework ◽  
Structural Phase ◽  
Metal Organic ◽  
Organic Framework

scholarly journals Flexibility of Metal-Organic Framework Tunable by Crystal Size at the Micrometer to Submillimeter Scale for Efficient Xylene Isomer Separation

Research ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Xiao Yang ◽  
Hao-Long Zhou ◽  
Chun-Ting He ◽  
Zong-Wen Mo ◽  
Jia-Wen Ye ◽  
...  
Keyword(s):  
Phase Transition ◽  
Crystal Size ◽  
Metastable Phase ◽  
Metal Organic Framework ◽  
High Energy ◽  
Isomer Separation ◽  
X Ray Diffraction ◽  
High Energy Barrier ◽  
Metal Organic ◽  
Xylene Isomers

Understanding, controlling, and utilizing the flexibility of adsorbents are of great importance and difficulty. Analogous with conventional solid materials, downsizing to the nanoscale is emerging as a possible strategy for controlling the flexibility of porous coordination polymers (or metal-organic frameworks). We report a unique flexibility controllable by crystal size at the micrometer to submillimeter scale. Template removal transforms [Cu2(pypz)2]·0.5p-xylene (MAF-36, Hpypz = 4-(1H-pyrazol-4-yl)pyridine) with one-dimensional channels to α-[Cu2(pypz)2] with discrete small cavities, and further heating gives a nonporous isomer β-[Cu2(pypz)2]. Both isomers can adsorb p-xylene to give [Cu2(pypz)2]·0.5p-xylene, meaning the coexistence of guest-driven flexibility and shape-memory behavior. The phase transition temperature from α-[Cu2(pypz)2] to β-[Cu2(pypz)2] decreased from ~270°C to ~150°C by increasing the crystal size from the micrometer to the submillimeter scale, ca. 2-3 orders larger than those of other size-dependent behaviors. Single-crystal X-ray diffraction showed coordination bond reconstitution and chirality inversion mechanisms for the phase transition, which provides a sufficiently high energy barrier to stabilize the metastable phase without the need of downsizing to the nanoscale. By virtue of the crystalline molecular imprinting and gate-opening effects, α-[Cu2(pypz)2] and β-[Cu2(pypz)2] show unprecedentedly high p-xylene selectivities of 16 and 51, respectively, as well as ultrafast adsorption kinetics (<2 minutes), for xylene isomers.

Strain-induced phase transitions in epitaxial NaNbO3thin films grown by metal–organic chemical vapour deposition

2012 ◽  
Vol 45 (5) ◽  
pp. 1015-1023 ◽  
Author(s):  
Jutta Schwarzkopf ◽  
Martin Schmidbauer ◽  
Thilo Remmele ◽  
Andreas Duk ◽  
Albert Kwasniewski ◽  
...  
Keyword(s):  
Phase Transition ◽  
Phase Transitions ◽  
Chemical Vapour Deposition ◽  
Vapour Deposition ◽  
Structural Phase ◽  
Chemical Vapour ◽  
Organic Chemical ◽  
Second Phase ◽  
X Ray Diffraction ◽  
Metal Organic

Epitaxially strained NaNbO3films were grown by liquid-delivery spin metal–organic chemical vapour deposition on several oxide substrates, inducing tensile and compressive lattice strain. High-resolution X-ray diffraction measurements reveal that coherently grown compressively strained NaNbO3films on NdGaO3exhibit the orthorhombiccphase. With increasing in-plane strain a first structural phase transition to the monoclinicrphase and, further on, for films grown under tensile strain on rare earth scandates, a second phase transition to theaaphase, are observed. Our results are in good agreement with the pathway of phase transitions predicted by Diéguez, Rabe & Vanderbilt [Phys. Rev. B, (2005),72, 144101] for NaNbO3films.

scholarly journals Structural phase transition of ternary dielectric SmGdO3: Evidence from angle dispersive x-ray diffraction and Raman spectroscopic studies

2015 ◽  
Vol 117 (9) ◽  
pp. 094101 ◽  
Author(s):  
Yogesh Sharma ◽  
Satyaprakash Sahoo ◽  
A. K. Mishra ◽  
Pankaj Misra ◽  
Shojan P. Pavunny ◽  
...  
Keyword(s):  
Phase Transition ◽  
Structural Phase Transition ◽  
Structural Phase ◽  
Spectroscopic Studies ◽  
X Ray Diffraction ◽  
X Ray ◽  
Raman Spectroscopic

scholarly journals Indexing PXRD Structural Parameters of Graphene Oxide-Doped Metal-Organic Frameworks

2019 ◽  
Vol 8 (2S9) ◽  
pp. 550-553
Keyword(s):  
Graphene Oxide ◽  
Structural Parameters ◽  
Metal Organic Framework ◽  
Synthesis Method ◽  
Vertical Direction ◽  
X Ray Diffraction ◽  
Metal Organic ◽  
Autogenous Pressure ◽  
Loading Amount

A family of metal-organic framework, [Mg3O3(CO2)3]∞ nanocrystallites which are also known as Mg-MOF-74, were synthesized by solvothermal method at high temperature under autogenous pressure. The graphene oxide was embedded into the framework via in-situ synthesis method to form a composite structure of Mg-MOF-74@nGO. n was varied from 0.1 to 0.6 wt% of the weight of pristine material. The synthesized samples were examined under Powder X-Ray Diffraction analysis to affirm their crystalline structure. Further studies were conducted by indexing the lattice parameters of the hexagonal crystals. The volume of unit cell and Scherrer’s crystallite size were also determined to study the effect of GO loading amount on their grown dimensions. The results showed that the presence of GO in the range of 0.1-0.6 wt% did not influence the dimension of the crystal except a slight expansion in vertical direction with the increment of GO loading.

scholarly journals Guest-Mediated Phase Transitions in a Flexible Pillared-Layered Metal-Organic Framework under High-Pressure

2021 ◽  
Author(s):  
Gemma Turner ◽  
Scott C. McKellar ◽  
David Robert Allan ◽  
Anthony K. Cheetham ◽  
Sebastian Henke ◽  
...  
Keyword(s):  
High Pressure ◽  
Phase Transitions ◽  
Single Crystal ◽  
Metal Organic Framework ◽  
Structural Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Metal Organic ◽  
Organic Framework

The guest-dependent flexibility of the pillared-layered metal-organic framework (MOF), Zn2bdc2dabco·X(guest), where guest = EtOH, DMF or benzene, has been examined by high-pressure single crystal X-ray diffraction. A pressure-induced structural phase...

Synthesis and Structure of a Clathrated Two-Dimensional Metal-Organic Framework: [Cd(4,4'-bpy)2(H2O)2](ClO4)2·(L)2·H2O (L = Bis(1-pyrazinylethylidene)hydrazine)

2008 ◽  
Vol 73 (1) ◽  
pp. 24-31
Author(s):  
Dayu Wu ◽  
Genhua Wu ◽  
Wei Huang ◽  
Zhuqing Wang
Keyword(s):  
Metal Organic Framework ◽  
Channel Structure ◽  
Two Dimensional ◽  
X Ray Diffraction ◽  
Guest Molecules ◽  
X Ray ◽  
Square Planar ◽  
Metal Organic ◽  
Aqueous Meoh ◽  
Organic Framework

The compound [Cd(4,4'-bpy)2(H2O)2](ClO4)2·(L)2 was obtained by the reaction of Cd(ClO4)2, bis(1-pyrazinylethylidene)hydrazine (L) and 4,4'-bipyridine in aqueous MeOH. Single-crystal X-ray diffraction has revealed its two-dimensional metal-organic framework. The 2-D layers superpose on each other, giving a channel structure. The square planar grids consist of two pairs of shared edges with Cd(II) ion and a 4,4'-bipyridine molecule each vertex and side, respectively. The square cavity has a dimension of 11.817 × 11.781 Å. Two guest molecules of bis(1-pyrazinylethylidene)hydrazine are clathrated in every hydrophobic host cavity, being further stabilized by π-π stacking and hydrogen bonding. The results suggest that the hydrazine molecules present in the network serve as structure-directing templates in the formation of crystal structures.

scholarly journals Preparation of Zn-MOFs by microwave-assisted ball milling for removal of tetracycline hydrochloride and Congo red from wastewater

2021 ◽  
Vol 10 (1) ◽  
pp. 125-133
Author(s):  
Qinhui Ren ◽  
Fuhua Wei ◽  
Hongliang Chen ◽  
Ding Chen ◽  
Bo Ding
Keyword(s):  
Ball Milling ◽  
Congo Red ◽  
Low Cost ◽  
Metal Organic Framework ◽  
Tetracycline Hydrochloride ◽  
Infrared Spectrometry ◽  
X Ray Diffraction ◽  
Wastewater Purification ◽  
Microwave Assisted ◽  
Metal Organic

Abstract In this study, we prepared Zn-MOFs as an ordinary, low-cost, and efficiency method taking advantage of zinc(ii) acetate monohydrate and 1,3,5-benzenetricarboxylic acid in microwave-assisted ball milling. The Zn-MOFs were measured via scanning electron microscopy, infrared spectrometry, X-ray diffraction, and thermogravimetry. We explored its use as a photocatalyst for the degradation of tetracycline hydrochloride and Congo red from aqueous solutions. The results demonstrate that the kinetic model was appropriate for the removal of organic pollutants. In general, it is feasible, inexpensive, and effective to use metal organic framework (MOF) to treat waste liquid. Therefore, our findings indicate that Zn-MOFs have broad application vista in wastewater purification.

Synthesis, crystal structure, luminescence, and photocatalytic properties of a 2D Cu(II) metal-organic frameworks based on 3,5-di(1H-benzimidazol-1-yl)pyridine and 4,4′-oxybis(benzoate) ligands

2020 ◽  
Vol 75 (8) ◽  
pp. 727-732
Author(s):  
Chen Zhang ◽  
Jian-Qing Tao
Keyword(s):  
Crystal Structure ◽  
Thermal Analysis ◽  
Uv Light ◽  
Metal Organic Framework ◽  
Metal Organic Frameworks ◽  
X Ray Diffraction ◽  
X Ray ◽  
Uv Light Irradiation ◽  
Photocatalytic Activities ◽  
Metal Organic

AbstractA new Cu(II) metal-organic framework, [Cu(L)(OBA)·H2O]n (1) [H2OBA = 4,4′-oxybis(benzoic acid), L = 3,5-di(1H-benzimidazol-1-yl)pyridine] was hydrothermally synthesized and characterized through IR spectroscopy, elemental and thermal analysis and single-crystal X-ray diffraction. Complex 1 is a four-connected uni-nodal 2D net with a (44·62) topology which shows an emission centered at λ ∼393 nm upon excitation at λ = 245 nm. Moreover, complex 1 possesses high photocatalytic activities for the decomposition of Rhodamine B (RhB) under UV light irradiation.

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