scholarly journals Structural Characterisation and Mechanical Stability of Titanium Substituted Mesoporous Materials

2010 ◽  
Vol 636-637 ◽  
pp. 136-141
Author(s):  
Cristina Galacho ◽  
Manuela M.L. Ribeiro Carrott ◽  
Joana Valerio ◽  
Peter J.M. Carrott ◽  
J.M. Valente Nabais
Keyword(s):  
Mesoporous Materials ◽  
Mechanical Stability ◽  
Nitrogen Adsorption ◽  
Mesoporous Structure ◽  
External Pressure ◽  
Molar Ratio ◽  
X Ray Diffraction ◽  
Hydrothermal Conditions ◽  
X Ray ◽  
Structural Characterisation

Mesoporous silica and titanium SBA-15 samples with different Si/Ti molar ratio were prepared by direct one-step synthesis under strongly acidic hydrothermal conditions. The materials were characterised by X-ray diffraction, nitrogen adsorption at 77K. The Si/Ti values of the final calcined materials were determined by ICP analysis. It was found that all samples presented 2-D hexagonal structures with high degree of ordering. However, the metal content incorporated in all titanium mesoporous materials was very low, i.e., the Si/Ti molar ratio values of the final calcined samples are significantly different from the initial Si/Ti molar ratio in the synthesis gel. A study of mechanical stability in air was performed by exposing the calcined samples to a unidirectional external pressure in the range 74-814MPa. X-ray diffraction and nitrogen adsorption at 77K, on selected compacted samples, were used in order to evaluate the changes in mesoporous structure. It was found that, for all freshly calcined pure silica and titanium containing samples tested, the high quality SBA-15 structure is still observed after the application 148-370MPa of a unidirectional external pressure and the collapse of the pore structure occurs at around 814MPa.

scholarly journals Compressibility Studies of Zirconium Based Metal-Organic Frameworks

2014 ◽  
Vol 70 (a1) ◽  
pp. C157-C157
Author(s):  
Claire Hobday ◽  
Stephen Moggach ◽  
Carole Morrison ◽  
Tina Duren ◽  
Ross Forgan
Keyword(s):  
High Pressure ◽  
Mechanical Stability ◽  
Metal Organic Frameworks ◽  
External Pressure ◽  
X Ray Diffraction ◽  
X Ray ◽  
X Ray Crystallography ◽  
Pressure Medium ◽  
Metal Organic ◽  
University Of Oslo

Metal-organic frameworks (MOFs) are a well-studied class of porous materials with the potential to be used in many applications such as gas storage and catalysis.[1] UiO-67 (UiO = University of Oslo), a MOF built from zirconium oxide units connected with 4,4-biphenyldicarboxylate (BDC) linkers, forms a face centred cubic structure. Zirconium has a high affinity towards oxygen ligands making these bridges very strong, resulting in UiO-based MOFs having high chemical and thermal stability compared to other MOF structures. Moreover, UiO-67 has become popular in engineering studies due to its high mechanical stability.[2] Using high pressure x-ray crystallography we can exert MOFs to GPa pressures, experimentally exploring the mechanical stability of MOFs to external pressure. By immersing the crystal in a hydrostatic medium, pressure is applied evenly to the crystal. On surrounding a porous MOF with a hydrostatic medium composed of small molecules (e.g. methanol), the medium can penetrate the MOF, resulting in medium-dependant compression. On compressing MOF-5 (Zn4O(BDC)3) using diethylformamide as a penetrating medium, the framework was shown to have an increased resistance to compression, becoming amorphous several orders of magnitude higher in pressure than observed on grinding the sample.[3] Here we present a high-pressure x-ray diffraction study on the UiO-based MOF UiO-67, and several new synthesised derivatives built from same metal node but with altered organic linkers, allowing us to study in a systematic way, the mechanical stability of the MOF, and its pressure dependence on both the linker, and pressure medium.

Synthesis and Structural Characterisation of a Hexanuclear TiIV Compound Ti6(μ2-O)2(μ3-O)2(μ2-OC4H9)2(OC4H9)6(OOCCHCl2)8

2010 ◽  
Vol 65 (2) ◽  
pp. 147-151 ◽  
Author(s):  
Ashutosh Pandey ◽  
Anjana Pandey ◽  
Sadhana Singh ◽  
Peter Mayer ◽  
Wolfgang J. Parakd
Keyword(s):  
Ambient Temperature ◽  
Toluene Solution ◽  
Dichloroacetic Acid ◽  
Molar Ratio ◽  
X Ray Diffraction ◽  
X Ray ◽  
Structural Characterisation ◽  
Hexanuclear Complex

Titanium tetra-butoxide was reacted with dichloroacetic acid in 1 : 1 and 1 : 2 molar ratio in toluene at ambient temperature to give, respectively, the mono- and bis-substituted products Ti(OBun)3(OOCCHCl2) and Ti(OBun)2(OOCCHCl2)2 (1) in quantitative yields. However, when a toluene solution of compound 1 was kept at −20 ◦C for crystallisation, colourless crystals of a hexanuclear complex Ti6(μ2-O)2(μ3-O)2(μ2-OC4H9)2(OC4H9)6(OOCCHCl2)8 (2) were obtained. The basic skeletal arrangement of compound 2, as revealed by X-ray diffraction, can be described as corner-removed, inversion-related [Ti-O]4 cubes with face-linked oxide bridges.

Size-Controllable Synthesis of Worm-Like SiO2 Microspheres Using Dodecylamine as Direct Agent in Ethanol/Water Solvent System

2013 ◽  
Vol 448-453 ◽  
pp. 154-159
Author(s):  
Xue Ling Zhang ◽  
Wei Yao Zhu ◽  
Meng Jing Cao ◽  
Qiang Cai ◽  
Xiao Feng Wang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Nitrogen Adsorption ◽  
Solvent System ◽  
Molar Ratio ◽  
X Ray Diffraction ◽  
Controllable Synthesis ◽  
Silica Microspheres ◽  
X Ray ◽  
Water Solvent ◽  
Transmission Electron

Size-controllable synthesis of worm-like microporous monodispersed SiO2microspheres using dodecylamine (DDA) as direct agent in ethanol-water solvent system was firstly developed by varying the proportion of reactants. The products were characterized with scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), small angle X-ray diffraction (SAXRD) and nitrogen adsorption. The results showed that the SiO2microspheres with size of 50nm~1um could be prepared by varying the molar ratio of water/ethanol when the molar ratio of (DDA)/tetraethyl orthosilicate (TEOS) is 0.4 and the concentration of TEOS varied from 0.138 to 0.248mol/L. This method is simple and convenient, the prepared SiO2microspheres are monodispersed and uniform, the worm-like pore size is about 1.4nm. The size controllable silica microspheres could be used as an excellent additional medium to alter rheological behavior of fluid after surface modification..

Morphological and Structural Analyses in Carbonated Magnesium-Aluminum Hydrotalcites Co-Substituted with Iron III

2018 ◽  
Vol 930 ◽  
pp. 26-31
Author(s):  
Creuza Kimito Caceres Kawahara ◽  
Graciele Vieira Barbosa ◽  
Igor Silva de Sá ◽  
Sabrina Vitor Gonçalves ◽  
Rafael Aparecido Ciola Amoresi ◽  
...  
Keyword(s):  
High Temperatures ◽  
Nitrogen Adsorption ◽  
Mesoporous Structure ◽  
Precipitation Process ◽  
X Ray Diffraction ◽  
X Ray ◽  
Co Substitution ◽  
Trivalent Cations ◽  
Adsorption Desorption ◽  
Positive Results

Magnesium-aluminum hydrotalcites can be co-substituted with others trivalent cations, such as iron III in aluminum site, which can be a promising way to modify the properties of that synthetic adsorptive material. In the present work, hydrotalcite containing 5 mol% iron III in co-substitution to the aluminum was prepared by precipitation process and compared with no co-substituted sample along the temperature of calcination at 100 and 500 oC for 4 hours. The calcined samples were characterized by simultaneous TG/DTA, X-ray Diffraction and nitrogen adsorption-desorption techniques. The iron (III) insertion showed positive results in order to provide more stable structure against high temperatures of calcination, which was observed by lesser structural decomposition of rhombohedral hydrotalcite and a more mesoporous structure.

Mechanical Stability of Pure Silica Mesoporous MCM-41 by Nitrogen Adsorption and Small-Angle X-ray Diffraction Measurements

1996 ◽  
Vol 100 (6) ◽  
pp. 1985-1988 ◽  
Author(s):  
Vladimir Yu. Gusev ◽  
Xiaobing Feng ◽  
Zimei Bu ◽  
Gary L. Haller ◽  
James A. O'Brien
Keyword(s):  
Small Angle ◽  
Mechanical Stability ◽  
Nitrogen Adsorption ◽  
X Ray Diffraction ◽  
X Ray ◽  
Pure Silica ◽  
Mcm 41

Effect of Hydrated Metal Salts on the Coordination Product of Cobalt(II) halide and PNP Type Ligand, 2,6-bis(di-tertbutylphosphinomethyl) pyridine

2018 ◽  
Author(s):  
Tasneem Siddiquee ◽  
Abdul Goni
Keyword(s):  
Metal Salts ◽  
Molar Ratio ◽  
Pincer Complexes ◽  
Asymmetric Unit ◽  
X Ray Diffraction ◽  
Pincer Ligand ◽  
Tetrahedral Geometry ◽  
X Ray ◽  
Distorted Tetrahedral Geometry ◽  
Cobalt Center

Chemical treatment of CoX<sub>2</sub><b><sup>. </sup></b>6H<sub>2</sub>O (X = Cl, Br, I) with the potentially tridentate PNP pincer ligand 2,6-bis(di-<i>tert</i>-butylphosphinomethyl)pyridine in 1:1 molar ratio results in cobalt(II) halide-PNP pincer complexes. The effect of the hydrated metal source on molecular structure and geometry of the complexes was studied by single crystal X-ray diffraction analysis. The complexes are neutral and the cobalt center adopts a penta-coordinate system with potential atropisomerization. Within the unit cell there are two distinct molecules per asymmetric unit. One of the two phosphorus atoms in the PNP ligand was observed to be partially oxidized to phosphinoxide. Disorder in the structure reflects a mixture of square pyramidal and distorted tetrahedral geometry.

scholarly journals An investigation of polyhedral deformation in two mixed-metal diarsenates: SrZnAs2O7and BaCuAs2O7

2015 ◽  
Vol 71 (4) ◽  
pp. 330-337 ◽  
Author(s):  
Sabina Kovač ◽  
Ljiljana Karanović ◽  
Tamara Đorđević
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
General Formula ◽  
Three Dimensional ◽  
X Ray Diffraction ◽  
Hydrothermal Conditions ◽  
X Ray ◽  
Open Framework ◽  
Geometrical Characteristics ◽  
Barium Copper

Two isostructural diarsenates, SrZnAs2O7(strontium zinc diarsenate), (I), and BaCuAs2O7[barium copper(II) diarsenate], (II), have been synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction. The three-dimensional open-framework crystal structure consists of corner-sharingM2O5(M2 = Zn or Cu) square pyramids and diarsenate (As2O7) groups. Each As2O7group shares its five corners with five differentM2O5square pyramids. The resulting framework delimits two types of tunnels aligned parallel to the [010] and [100] directions where the large divalent nine-coordinatedM1 (M1 = Sr or Ba) cations are located. The geometrical characteristics of theM1O9,M2O5and As2O7groups of known isostructural diarsenates, adopting the general formulaM1IIM2IIAs2O7(M1II= Sr, Ba, Pb;M2II= Mg, Co, Cu, Zn) and crystallizing in the space groupP21/n, are presented and discussed.

Selective oxidation of cyclopentene to glutaraldehyde by H2O2 over Nb-SBA-15

2021 ◽  
Author(s):  
yingmeng qi ◽  
Qi Han ◽  
li wu ◽  
Jun Li
Keyword(s):  
Structural Properties ◽  
Selective Oxidation ◽  
Mesoporous Materials ◽  
Hydrothermal Process ◽  
X Ray Diffraction ◽  
X Ray

A series of niobium-containing mesoporous materials Nb-SBA-15 have been prepared by sonication–impregnation and hydrothermal process. The dispersion and structural properties of niobium-containing species were systematically characterized by X-ray diffraction, scanning...

scholarly journals Photocatalytic Reduction of CO2 to Methanol Using a Copper-Zirconia Imidazolate Framework

Catalysts ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 346
Author(s):  
Sonam Goyal ◽  
Maizatul Shima Shaharun ◽  
Ganaga Suriya Jayabal ◽  
Chong Fai Kait ◽  
Bawadi Abdullah ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Catalyst Support ◽  
Oxidation Potential ◽  
Molar Ratio ◽  
X Ray Diffraction ◽  
X Ray ◽  
Molar Ratios ◽  
Optimum Parameters ◽  
Reduction Of Co2 ◽  
Enhanced Yield

A set of novel photocatalysts, i.e., copper-zirconia imidazolate (CuZrIm) frameworks, were synthesized using different zirconia molar ratios (i.e., 0.5, 1, and 1.5 mmol). The photoreduction process of CO2 to methanol in a continuous-flow stirred photoreactor at pressure and temperature of 1 atm and 25 °C, respectively, was studied. The physicochemical properties of the synthesized catalysts were studied using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and photoluminescence (PL) spectroscopy. The highest methanol activity of 818.59 µmol/L.g was recorded when the CuZrIm1 catalyst with Cu/Zr/Im/NH4OH molar ratio of 2:1:4:2 (mmol/mmol/mmol/M) was employed. The enhanced yield is attributed to the presence of Cu2+ oxidation state and the uniformly dispersed active metals. The response surface methodology (RSM) was used to optimize the reaction parameters. The predicted results agreed well with the experimental ones with the correlation coefficient (R2) of 0.99. The optimization results showed that the highest methanol activity of 1054 µmol/L.g was recorded when the optimum parameters were employed, i.e., stirring rate (540 rpm), intensity of light (275 W/m2) and photocatalyst loading (1.3 g/L). The redox potential value for the CuZrIm1 shows that the reduction potential is −1.70 V and the oxidation potential is +1.28 V for the photoreduction of CO2 to methanol. The current work has established the potential utilization of the imidazolate framework as catalyst support for the photoreduction of CO2 to methanol.

A 2-D Zn(II) coordination polymer based on 4,5-imidazoledicarboxylate and bis(benzimidazole) ligands: synthesis, crystal structure and fluorescence properties

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Xinzhao Xia ◽  
Lixian Xia ◽  
Geng Zhang ◽  
Yuxuan Jiang ◽  
Fugang Sun ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Coordination Polymer ◽  
Zigzag Chain ◽  
Supramolecular Framework ◽  
X Ray Diffraction ◽  
Hydrothermal Conditions ◽  
Hydrogen Bond Interaction ◽  
X Ray ◽  
New Type ◽  
Solid State Fluorescence

Abstract In this work, a new type of zinc(II) coordination polymer {[Zn(HIDC)(BBM)0.5]·H2O} n (Zn-CP) was synthesized using 4,5-imidazoledicarboxylic acid (H3IDC) and 2,2-(1,4-butanediyl)bis-1,3-benzimidazole (BBM) under hydrothermal conditions. Its structure has been characterized by infrared spectroscopy, elemental analysis and single crystal X-ray diffraction analysis. The Zn(II) ion is linked by the HIDC2− ligand to form a zigzag chain by chelating and bridging, and then linked by BBM to form a layered network structure. Adjacent layers are further connected by hydrogen bond interaction to form a 3-D supramolecular framework. The solid-state fluorescence performance of Zn-CP shows that compared with free H3IDC ligand, its fluorescence intensity is significantly enhanced.

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