Well-Dispersed H₃PW₁₂O₄₀/H₄SiW₁₂O₄₀ Nanoparticles on Mesoporous Polymer for Highly Efficient Acid-Catalyzed Reactions

Abstract

With the depletion of fossil fuels, development of renewable energy has attracted wide attention in recent years. The well-known polyoxometalates (POMs) of H3PW12O40 (denoted as PW12) and H4SiW12O40 (denoted as SiW12) are effective catalysts for acid-catalyzed reactions. Nevertheless, industrial application of PW12 and SiW12 is largely restricted by the agglomeration, separation, leaching and recycling issues. Moreover, the PW12 and SiW12 tend to deactivate strong proton sites due to the small surface area of 10 m2·g–1. To overcome these problems, the PW12 and SiW12 have been fabricated onto a mesoporous polymer of PDVB-VBC (compound 1) with a large surface area via tris­(2-aminoethyl)­amine (TAEA), resulting in the formation of new heterogeneous catalysts of PDVB-VBC-TAEA-PW12 (compound 3) and PDVB-VBC-TAEA-SiW12 (compound 4). Both compounds 3 and 4 possess mesoporous structures with high surface area of 121 m2·g–1 and 131 m2·g–1, respectively. And they have shown highly efficient and selective dehydration of fructose to 5-hydroxymethylfurfural (5-HMF) in dimethyl sulfoxide (DMSO) as well as esterification of lauric acid (LA) to methyl laurate. Moreover, the catalysts can be recycled for at least five times with no obvious decrease of reactivity. Therefore, such catalysts have great potential for further application from a chemical engineering point of view.

Amelioration of H4[W12SiO40] by nanomagnetic heterogenization: For the synthesis of 1H–pyrazolo[1,2‐b]phthalazinedione derivatives

“…A mechanism of the synthesis of 1 H –pyrazolo[1,2‐ b ]phthalazinedione derivatives catalysed by the STA‐Amine‐Si‐Magnetite nanoparticles is proposed, as shown in Scheme . Heteropoly acids play a role similar to that of Brønsted acids in catalysis . Initially, STA protonates the carbonyl group of the aldehyde which further undergoes Knoevenagel condensation with malanonitrile.…”

“…Heteropoly acids play a role similar to that of Brønsted acids in catalysis. [23,51,52] Initially, STA protonates the carbonyl group of the aldehyde [53] which further undergoes Knoevenagel condensation with malanonitrile. Further, Michael addition of phthalhydrazide to C═C bond of the Knoevenagel product followed by cyclization results in the formation of desired product.…”

Facile synthesis of polyoxometalates tethered to post Fe-BTC frameworks for esterification of free fatty acids to biodiesel

“…22 In order to overcome these disadvantages, the exchange of protons of HPAs with different cations results in formation of insoluble salts and the immobilization of HPAs could be acted as efficient strategy for the catalytic reaction. Now, different supports have been explored to design HPA-immobilized solid acid catalysts for various organic transformations, including SiO 2 , 23 montmorillonite K10, 24 mesoporous polymer of PDVB-VBC, 25 or MCM-41. 26 Unfortunately, the high solubility of HPAs in polar solvents and weak interaction between active HPAs and supported makes it relatively difficult to be immobilized on the above materials.…”

Enhanced recovery and recycling of catalyst by post‐impregnation of γ‐Al2O3 with 12‐tungstophosphoric acid for esterification reaction

“…In terms of practical concerns, polyoxometalates (POM) have application in analytical and clinical chemistry, catalysis, photocatalysis, biochemistry, medicine (antitumoral, antiviral), and solid‐state devices . Especially tungstophosphoric acid (H 3 PW 12 O 40 , HPW) with Keggin structure has been used as an important acid catalyst with Brønsted acidity in clean catalytic reactions, because of high catalytic activity, good stability, and physiochemical properties . Hence, a new trend toward the application of these remarkable species in catalysis is beginning to evolve.…”

“…[15,16] Especially tungstophosphoric acid (H 3 PW 12 O 40 , HPW) with Keggin structure has been used as an important acid catalyst with Brønsted acidity in clean catalytic reactions, because of high catalytic activity, good stability, and physiochemical properties. [17,18] Hence, a new trend toward the application of these remarkable species in catalysis is beginning to evolve. These materials can replace the corrosive acids.…”