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How do the acid strengths of polyoxometalates compare to those of other acids?

Phosphotungstic acid

Silicotungstic acid

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Polyoxometalates (POMs) have been found to possess controlled Brønsted and Lewis acidity, which makes them suitable as acid catalysts for various organic reactions. POMs exhibit high thermal stability, nontoxic nature, tunable solubility, and less corrosiveness, making them attractive for industrial applications . In terms of acid strength, POMs have been shown to have super strong Bransted acidity, which is beneficial for acid-catalyzed reactions . The acid strength of POMs can be further influenced by factors such as the type of POM used and the support material. For example, phosphotungstic acid (HPW) has been found to have higher acid strength compared to silicotungstic acid (HSiW) and phosphomolybdic acid (HPMo) . Overall, POMs offer a promising alternative to conventional homogeneous acid catalysts due to their favorable acid strength and other advantageous properties.

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Journal Article•DOI Synthesis of polyoxometalates supported on HZSM-5 for the photocatalytic purification of crude terephthalic acid under mild conditions A. M. Hussein, A.H. Mady, A.H. Mady, Sawsan S. Mahmoud, Jae-Jin Shim, F.Z. Yehia - Show less +5 more 15 May 2019-Journal of Photochemistry and Photobiology A-chemistry 6 Citations	The text does not provide information about how the acid strengths of polyoxometalates compare to those of other acids.
Journal Article•DOI Polyoxometalates entrapped in sol-gel matrices as electron exchange columns and catalysts for the reductive de-halogenation of halo-organic acids in water Neelam, Dan Meyerstein, Dan Meyerstein, Ariela Burg, Dror Shamir, Yael Albo - Show less +5 more 19 Sep 2018-Journal of Coordination Chemistry 3 Citations	The acid strengths of polyoxometalates are not mentioned in the provided information.
Open access•Dissertation Polyoxometalates as solid acid catalysts for sustainable chemistry Lucia Frattini 01 Jan 2017	The acid strengths of polyoxometalates were found to decrease in the order of HPW>HSiW>HPMo, which is independent of the support.
Journal Article•DOI Polyoxometalates-based heterogeneous catalysts in acid catalysis Lifei Lian, Huaiying Zhang, Sai An, Wei Chen, Yu-Fei Song - Show less +4 more 20 May 2021-Science China-chemistry 29 Citations	Polyoxometalates have super strong Bransted acidity, making them potential green alternatives to conventional homogeneous acid catalysts.

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