Synthesis and characterization of copper hydroxide acetate with a layered discoid crystal
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Sridhar Komarneni Department of Crop and Soil Sciences and Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania, 16802 (Received 8 November 2004; accepted 26 July 2005)
Titration of copper acetate solution with a dilute NaOH solution to pH 6.5 and subsequent aging at 313 K yielded copper hydroxide acetate with an analytical composition of Cu2(OH)3.1(OCOCH3)0.9nH2O (n ∼ 0.7) and layered discoid crystals. The chemical composition, structure, and holistic trend in thermal behavior are similar to those of the previously known Cu2(OH)3(OCOCH3)H2O phase with layered rectangular crystals. The most obvious difference between the two compounds is morphology of the crystals. The other major differences are found in stability of bonding of the interlayer acetate ions to solid phase and behavior in anion-containing solutions. The interlayer acetate ions in the present compound begin to be dissociated from the solid phase at ∼343 K while those in the previous compound are not dissociated below 383 K. The reaction of the present compound is topotactic in Cl− and NO3− aqueous solutions but reconstructive in a SO42− aqueous solution while the reaction of the previous compound in those solutions is topotactic.
I. INTRODUCTION
Anion-exchangeable layered compounds have attracted intense attention as hosts for organic and inorganic anions. The most studied anion-exchangeable layered compounds are layered double hydroxides (LDHs). The representative group of LDHs has the formula [M2+xM3+1−x(OH)2]x+Yz−x/z·nH2O, where M2+ and M3+ are cations and Yz− is anion, and the brucite [Mg(OH)2]like trioctahedral structure.1,2 In this brucite-like LDH, the positive charge is generated by the isomorphous substitution of trivalent cations for a fraction of divalent cations. Another group of LDHs has the formula Al2Li(OH)6Yz−1/z·nH2O and gibbsite [Al(OH)3]-like dioctahedral structure.3 In the gibbsite-like LDH, the positive charge is generated by the incorporation of lithium ion into vacancies in the Al(OH)6 dioctahedral sheets. In both LDHs, all of the matrix cations are located between upper and lower hydroxide sheets. The positive charge is balanced by accommodating exchangeable anions Yz− in the interlayers of the layer structure. The bonding between the matrix cations and the interlayer anions is electrostatic through interjacent hydroxide sheets. a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2005.0366 J. Mater. Res., Vol. 20, No. 11, Nov 2005
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It is known that a part of layered transition metal hydroxide salts (LTMHSs) containing one or two kinds of divalent transition metal cations alone in matrix are anionexchangeable.4–9 They are simply called layered hydroxide (or basic) salt (LHS) when the salt contains one kind of divalent transition metal cation alone, or hydroxide (or hydroxy) double salt (HDS) when a fraction of the matrix cations in the salt are isomorphously substituted for a seco
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