Pillaring of layered double hydroxides with polyoxometalates in aqueous solution without use of preswelling agents
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By using wet samples of layered double hydroxides (LDHs), the direct pillaring reactions of these compounds with polyoxometalate (POM) ions with Keggin-type structure have been effected in an aqueous one-step reaction without any organic preswelling agents. 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. The Mg-Al series of LDHs gave products consisting of a well crystalline phase with a d spacing of 14.7 Å and a less crystalline phase with a lower and less-defined interlayer distance. The Ni-containing LDHs, Ni2Al(0H)6NO3for example, yielded pillared products that correspond to the latter phase with interlayer spacings ranging between 11.0 and 13.5 Å. The lowered interlayer distance is attributed to creation of defects in the layers as a result of strong interactions between POM and the LDH layers. Surface area measurement results are also presented. © 1992, American Chemical Society. All rights reserved.
author list (cited authors)
Wang, J., Tian, Y., Wang, R. C., & Clearfield, A.