Polyoxometalate

About: Polyoxometalate is a research topic. Over the lifetime, 3493 publications have been published within this topic receiving 94123 citations. The topic is also known as: POM.

Selective Oxidations on Recoverable Catalysts Assembled in Emulsions

Abstract: Catalysts assembled in emulsions are found to be potentially recoverable and efficient for a number of catalytic reactions. The catalysts composed of polyoxometalate anions and quaternary ammonium cations have been designed and synthesized according to the catalytic reactions and by optimizing the structures of cations and anions. The catalysts act essentially as surfactants, which are uniformly distributed in the interface of the emulsion droplets, and accordingly behave like homogeneous catalysts. The catalysts show remarkable selectivity and activity in the oxidation of sulfur-containing molecules to sulfones in diesel and the selective oxidation of alcohols to ketones, using H2O2 as oxidant. For an example, the catalyst demonstrated over 96% efficiency of H2O2 and ˜100% selectivity to sulfones for the selective oxidation of sulfur-containing molecules in real diesel. Moreover, the catalysts can be separated and recycled by a simple demulsification and re-emulsification.

Single-dispersed polyoxometalate clusters embedded on multilayer graphene as a bifunctional electrocatalyst for efficient Li-S batteries

Abstract: Abstract The redox reactions occurring in the Li-S battery positive electrode conceal various and critical electrocatalytic processes, which strongly influence the performances of this electrochemical energy storage system. Here, we report the development of a single-dispersed molecular cluster catalyst composite comprising of a polyoxometalate framework ([Co 4 (PW 9 O 34 ) 2 ] 10− ) and multilayer reduced graphene oxide. Due to the interfacial charge transfer and exposure of unsaturated cobalt sites, the composite demonstrates efficient polysulfides adsorption and reduced activation energy for polysulfides conversion, thus serving as a bifunctional electrocatalyst. When tested in full Li-S coin cell configuration, the composite allows for a long-term Li-S battery cycling with a capacity fading of 0.015% per cycle after 1000 cycles at 2 C (i.e., 3.36 A g −1 ). An areal capacity of 4.55 mAh cm −2 is also achieved with a sulfur loading of 5.6 mg cm − 2 and E/S ratio of 4.5 μL mg −1 . Moreover, Li-S single-electrode pouch cells tested with the bifunctional electrocatalyst demonstrate a specific capacity of about 800 mAh g −1 at a sulfur loading of 3.6 mg cm −2 for 100 cycles at 0.2 C (i.e., 336 mA g −1 ) with E/S ratio of 5 μL mg −1 .

Polyoxometalate built-in conjugated microporous polymers for visible-light heterogeneous photocatalysis

Abstract: Herein, we report two novel Anderson-type polyoxometalate (POM) built-in conjugated microporous polymers (CMPs), Bn-Anderson-CMP and Th-Anderson-CMP prepared through Sonogashira–Hagihara cross-coupling of tetrabromo-bifunctionalized Anderson-type POMs and 1,3,5-triethynylbenzene. These two Anderson-CMPs exhibit outstanding heterogeneous photocatalytic activities towards degrading organic dyes in water. Control photocatalysis experiments with different radical scavengers demonstrate that hydrogen peroxide and singlet oxygen are the primary active catalytic species. Moreover, these two CMPs can be easily recycled at least five times without a noticeable decrease in photocatalytic performances.

Hydrothermal Synthesis and Characterization of a Novel Sinusoidal Layer Structure Constructed From Polyoxometalates and Coordination Complex Fragments

Abstract: A novel polyoxometalate compound, [As8V14O42(SO4)][Ni(en)2]3·4.5H2O (1), has been synthesized by a hydrothermal method and characterized by X-ray crystallography, showing that the compound 1 is the first example of a sinusoidal layer structure constructed from polyoxometalates and coordination complex fragments. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

One‐pot, One‐step Synthesis of 2,5‐Diformylfuran from Carbohydrates over Mo‐Containing Keggin Heteropolyacids

Abstract: In this work, a one-pot strategy for directly converting fructose into 2,5-diformylfuran (DFF) over Mo-containing Keggin heteropolyacids (HPAs) in open air is developed. H3 PMo12 O40 HPA is found to show high activity and selectivity to the formation of DFF owing to its higher Bronsted acidity and moderate redox potential. The partial substitution of the H(+) in H3 PMo12 O40 with Cs(+) leads to the heterogenization of the HPA by forming its cesium salts Csx H3-x PMo12 (x=0.5, 1.5, and 2.5). A satisfactory yield of 69.3% to DFF is obtained over Cs0.5 H2.5 PMo12 polyoxometalate after deliberate optimization of the reaction conditions. The heterogenized polyoxometalate could be recycled and reused without significant loss of catalytic activity for five runs. The produced DFF could be separated from the resulting mixture by an adsorption-desorption method using activated carbon as the adsorbent and furfural as the desorbent. A highest isolated yield of 58.2% is obtained.