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Systematic Preparation Of Polyoxometalate Pillared Layered Double Hydroxides Via Direct Aqueous Reaction

Published online by Cambridge University Press:  15 February 2011

Jiandang Wang
Affiliation:
Department of Chemistry, Texas A&M University College Station, Texas 77843
Ying Tian
Affiliation:
Department of Chemistry, Texas A&M University College Station, Texas 77843
Ren-Chain Wang
Affiliation:
Department of Chemistry, Texas A&M University College Station, Texas 77843
Jorge L. Colón
Affiliation:
Department of Chemistry, Texas A&M University College Station, Texas 77843
Abraham Clearfield
Affiliation:
Department of Chemistry, Texas A&M University College Station, Texas 77843
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Abstract

The series of layered double hydroxides, MgnAl(OH)2n+2X (n = 2–5, X = NO3 or Cl) and NinAl(OH) 2n+2X (n = 2–4, X = NO3 or Cl), were pillared with polyoxometalate ions of the Keggin structure, ranging from [PW12O40]3− to [PV4W8O40]7−, in aqueous solution. Full exchange of the Keggin ions into the layers is achieved as evidenced by X-ray powder diffraction, infrared spectroscopy, elemental analysis and thermogravimetric analysis. Also, partial exchange was observed for Ni5Al(OH)12NO3 The key factor that effects these reactions is the pre-swelling step. Thus, when the layered double hydroxides are thoroughly wet either by preparing wet solids or by soaking the dried products for an extended period, pillaring reactions proceed with great ease. Relations can be extracted between the water content and the separation between the layers, as well as between layer charge density and the charge of the Keggin ion. The pillared layered double hydroxides were found generally to have interlayer distances ranging from 11.0 to 13.5 Å, which is smaller than the numerical sum of the Keggin ion diameter and the ideal thickness of the hydroxide layer. This fact and the low crystallinity are attributed to strong interaction between the basic layered double hydroxides and the acidic Keggin ions. A more crystalline phase with the expected 14.5 Å interlayer spacing was also obtained as a mixture with the lower spaced products.

Type
Research Article
Copyright
Copyright © Materials Research Society 1991

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References

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