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polyoxometalate
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Novel keggin-type polyoxometalate nanocatalysts for michael addition polymerizations
, Article Materials Chemistry and Physics ; Volume 199 , 2017 , Pages 79-87 ; 02540584 (ISSN) ; Pourayoubi, M ; Bakhshi, H ; Sharif University of Technology
Abstract
Keggin-type polyoxometalate (POM) nanoparticles based on [PW12O40]3- and [SiW12O40]4- with Ag+ and (ZrO)2+ cations were prepared under ultrasound irradiation. The results of SEM and XRD revealed the average size of particles in the range of 24–95 nm. The moles of crystallization water per mole of nanocatalysts were in the range of 3–9. EDX spectra confirmed the successful replacement of protons of H3PW12O40 and H4SiW12O40 with Ag+ and (ZrO)2+ cations. These nanoparticles were used as heterogeneous catalysts for the synthesis of a poly (amido-ester) at room temperature. All polymers were fully characterized. Although employing the nanocatalyst resulted in at least 22% improvement in the...
Simple solid state synthesis of nanostructured Ag6Mo10O33 and ni- substituted Ag6Mo10O33 polyoxometalates with photocatalytic characteristic
, Article Iranian Journal of Materials Science and Engineering ; Volume 14, Issue 3 , 2017 , Pages 48-53 ; 17350808 (ISSN) ; Imani, M ; Irajizad, A ; Sharif University of Technology
Abstract
In this work, we report the synthesis of silver decamolybdate, Ag6Mo10O33, nanostructure by a simple mechanochemical process followed by calcination treatment using acetamide as driving agent. Morphological study by scanning electron microscopy (SEM) images revealed bundles of rods grown closely together with an average diameter of 92 nm for Ag6Mo10O33 sample. Ni-substituted Ag6Mo10O33 compound was prepared via introducing nickel cation to precursor system in mechanical milling step. The particle size decreased to 87 nm by incorporating nickel units in substituted polymolybdate. It was concluded that the suitable selection of reagents can direct solid phase reaction towards producing...
Nanostructured molybdenum oxide in a 3D metal organic framework and in a 2D polyoxometalate network for extraction of chlorinated benzenes prior to their quantification by GC–MS
, Article Microchimica Acta ; Volume 185, Issue 12 , 2018 ; 00263672 (ISSN) ; Karimi Zandian, F ; Javanmardi, H ; Abbasi, A ; Golzari Aqda, T ; Sharif University of Technology
Abstract
A three–dimensional metal organic framework (3D–MOF) and a two–dimensional polyoxometalate (2D–POM), both incorporating nanostructured molybdenum (VI) oxide, were synthesized and implemented for headspace needle trap extraction of traces of chlorobenzenes (CBs). The 3D–MOF of type {(Mo2O6)(4,4′–bpy)}n and the 2D–POM of type [4,4′–bpy][Mo7O22] were synthesized by a solvothermal process and characterized by FT–IR, powder X–ray diffraction, scanning electron microscopy, transmission electron microscopy, thermogravimetry, energy dispersive X–ray, elemental mapping and Brunner–Emmet–Teller adsorption analyses. The 3D–MOF proved to be superior. Following thermal desorption, the CBs...
H2S gasochromic effect of mixed ammonium salts of phosphomolybdate nanoparticles synthesized by microwave assisted technique
, Article Sensors and Actuators, B: Chemical ; Volume 237 , 2016 , Pages 715-723 ; 09254005 (ISSN) ; Iraji zad, A ; Tadjarodi, A ; Sharif University of Technology
Elsevier B.V
2016
Abstract
In the present paper, new H2S gasochromic nanomaterial of mixed silver nickel ammonium phosphomolybdate synthesized by microwave assisted technique is reported. The microwave treatment was performed in the solid phase using urea and ammonium nitrate as the promoter and oxidizer agents. The designed process allows rapid synthesis of large amounts of this product in nanosized particulate morphology. Morphological and structural features of the prepared products were studied in detail. Chemical analyses indicated a stoichiometry of (NH4)0.5Ni0.75AgPMo12O40·4H2O revealing a Keggin-type framework with substitution of silver and nickel cations in its secondary structure. A home-made set-up was...
Polyoxometalate-supported Pd nanoparticles as efficient catalysts for the Mizoroki-Heck cross-coupling reactions in PEG medium
, Article Applied Organometallic Chemistry ; Volume 34, Issue 1 , 2020 ; Hosseini, H ; Salami, R ; Sharif University of Technology
John Wiley and Sons Ltd
2020
Abstract
Palladium nanoparticles supported on polyoxometalate as a solid carrier were successfully prepared and evaluated as a heterogeneous nanocatalyst for the Mizoroki-Heck cross-coupling reactions. This supported catalyst was characterized by a set of techniques, including XRD, chemical analysis (ICP-OES), IR spectroscopy, TEM and FE-SEM analyses. Poly (ethylene glycol) was employed as an environmentally friendly solvent for coupling reactions. The various fundamental reaction parameters that influence the efficiency of the reaction and yield of the desired reaction products were optimized. This catalytic system showed good activities and evolve a strategy for achieving five times catalyst and...
Synthesis, Characterization and Voltametric Study of Single Molecule Magnet Hybrid Salts [Mn3O(O2CMe)6(Pyr)3][Keggin-Polyoxometalates]Type
,
M.Sc. Thesis
Sharif University of Technology
;
Mohammadi Boghaei, Davar
(Supervisor)
Abstract
Molecular nanomagnets, also known as Single Molecule Magnets (SMMs) are a class of molecules that at low temperature exhibit magnetic hysteresis of pure molecular origin and not related to a cooperative effect. In the past fifteen years they have attracted great interest for their potentiality to act as magnetic memory units and for the many quantum effects in the dynamics of their magnetization. Organization of SMM on surfaces is the first step in order to address the magnetic state of a single molecule or to connect the molecule to a conducting substrate. The complex nature of SMMs and the peculiar origin of their magnetic bistability have been representing for half a decade an obstacle to...
Synthesis and Properties of Cationic Polynulcear Complexes of Manganese with the Anionic Keggin Type Polyoxometalates as Single Molecule Magnets Hx[Mn4O2(CH3COO)7(bipy)2]n[Kegiin-Polyoxometalates]m.yH2O
, M.Sc. Thesis Sharif University of Technology ; Mohammdi Boghaei, Davar (Supervisor)
Abstract
Single molecule magnets due to their magnetic tunneling effect and the interaction they have with an external magnetic field are used widely in quantum computing and also the storage of data with high capacities. Polyoxometalates that are used as counter ions for cationic single molecule magnets, are able to affect their spin-couple nature via a magnetic exchange and also have an influence on the crystal accumulation in order to change the magnetic property of the molecule. In this research the probability of sedimenting a cationic single molecule magnet, [Mn4O2(CH3COO)7(bipy)2]+, with the use of anionic polyoxometalates with Keggin structures has been investigated. Thus, the single...
Preparation, Characterization and Catalytic Application of Some Polyoxometalates for Esterification Reaction
, M.Sc. Thesis Sharif University of Technology ; Rahman Setayesh, Shahrbanoo (Supervisor)
Abstract
Catalytic esterification of acetic acid with 1-hexanol was investigated over polyoxometalates. H3PW12O40 and H3PMo6W6O40 polyoxometalates with keggin structures were synthesized. Catalytic activity and recyclability of them were improved by loading on the γ-Al2O3 with impregnation method and Cs, K and NH4 salts preparing.Catalysts were characterized by XRD, SEM, FT-IR, BET, DRS and NMR techniques. According to XRD's results, catalysts have ace-centered cubic crystal systems. Loading on supports and preparing the salts do not destroy the structures of polyoxometalates. SEM images show the uniformity of catalysts' surface and catalysts' fixing on the support. It was seen that the keggin...
Enhanced recovery and recycling of catalyst by post-impregnation of γ-Al2O3 with 12-tungstophosphoric acid for esterification reaction
, Article Canadian Journal of Chemical Engineering ; Volume 96, Issue 5 , 2018 , Pages 1176-1184 ; 00084034 (ISSN) ; Rahman Setayesh, S ; Sharif University of Technology
Wiley-Liss Inc
2018
Abstract
12-tungstophosphoric acid, polyoxometalate with Keggin structure, and γ-Al2O3 were synthesized. Loading of 12-tungstophosphoric acid (HPW) on γ-Al2O3 was performed by the post-impregnation method. The catalysts were characterized by XRD, SEM, FTIR, BET, and DRS techniques. According to the pertinent observation, using the post-impregnation method promises the stability of polyoxometalate Keggin structure after loading on γ-Al2O3 support. The stability of 20 %HPW/Al2O3 was also confirmed by a leaching test. Textural characterization demonstrates that HPW on the γ-Al2O3 had a much larger surface area as compared with the pure HPW. The 20 %HPW/Al2O3 exhibited roughly high activity toward an...
Synthesis and Characterization of Nanocluster Polyoxometalates as Catalysts in Oxidation and Coupling Reactions
, Ph.D. Dissertation Sharif University of Technology ; Bagherzadeh, Mojtaba (Supervisor)
Abstract
In this study, a series of polyoxometalates nanoclusters is synthesized and their catalytic properties have been investigated in oxidation and coupling reactions. In the first and second sections, {Mo36} nanoclusters are primarily prepared. Then, the mesoporous silica, as a solid surface with a regular chanals and cavities through electrostatic interactions between polyoxo anions and amine functional groups with positive charge, is used to stabilize the nanocluster as well as the final structure of SBA-15-NH3 +•{Mo36}- formed. As a green and environmentally friendly substrate, natural zeolite is used to stabilize the nanoclusters and the {Mo36}@zeolite obtained. Both heterogeneous catalysts...
Pereparation, Characterization and Photocatalytic Application of Some Polyoxometalates in Degradation of Oraganic Pollutants
, M.Sc. Thesis Sharif University of Technology ; Rahman Setayesh, Shahrbanoo (Supervisor)
Abstract
In this project photocatalysts TiO2, H3PW12O40, H3PMo6W6O40, H3PW12O40 / TiO2, H3PMo6W6O40 / TiO2, K2.5H0.5PW12O40, Cs2.5H0.5PW12O40, (NH4) 2.5H0.5PW12O40 and H3PW12O40 / M-TiO2 that M = La , Ce, Cr, Fe, Co were characterized by techniques DRS, FT-IR, BET, 31P NMR, SEM and XRD. The results of SEM and XRD particle size and page crystalline nanoscale catalysts, with size less than 40nm, respectively. FT-IR analysis confirmed the structure of heteropolyacid was produced. DRS analysis of the degradation reactions during wavelenght longer upheld. Degradation of methylene blue and pollutants such as Tinopal CBS-x to the polyoxometalates keggin is homogeneous and composite titanium dioxide two...
Synthesis of a MOF Supported Polyoxotungstate and its Application as Catalyst in C-C Coupling Reaction
, M.Sc. Thesis Sharif University of Technology ; Bagherzadeh, Mojtaba (Supervisor)
Abstract
In this study, a polyoxotungestate containing copper was impregnated as catalyst on a magnetic metal-organic framework (Fe3O4/MIL-101(Cr)). Initially, the desired polyoxotungestate was synthesized using sodium tungestate and sodium metasilicate salts and then copper(ІІ) ion was fixed on it. Subsequently, the MIL-101(Cr) metal-organic framework was prepared by solvothermal method; using chromium nitrate salt and 1,4-benzen dicarboxylic acid at 220 ◦C and was magnetized by co-precipitation method. Finally, the corresponding polyoxotungestate was stirred at ambient temperature for 24 h with MIL-101(Cr) and then the brown precipitate was separated using a magnet. Different techniques such as IR,...