Preparation of hydroxy double salts exchanged by organic compounds
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Preparation of hydroxy double salts exchanged by organic compounds Hiroyuki Morioka, Hideyuki Tagaya, Masa Karasu, Jun-ichi Kadokawa, and Koji Chiba Department of Materials Science and Engineering, Yamagata University, Jonan, Yonezawa, Yamagata 992, Japan (Received 17 September 1997; accepted 5 January 1998)
Hydroxy double salts (HDS’s) comprise a class of layered materials that are similar to layered double hydroxides (LDH’s) and show a comparable intracrystalline reactivity. Their anion exchange reactions occur with preincorporated anions in the hydroxide layer and with anions bound as gegenions of the positively charged layers, respectively. In this study, nitrate and acetate anions of HDS’s were exchanged with anionic monoand di-carboxylic acids, and we confirmed that interlayer spacing of HDS’s increased depending on the size of mono- and di-carboxylic acids. Moreover, we have prepared photofunctional materials by exchange reaction with azobenzene-p-carboxylic acid and 4-40 -azobenzenedicarboxylic acid.
I. INTRODUCTION
Layered metal hydroxides are of great interest to both science and technology, because of their utility as an ion-exchange material,1 catalyst,2 antacid, and magnetic materials.3 Layered double hydroxide4 (LDH) and hydroxy double salt5 (HDS) are known as anion exchangeable compounds. The general formula of LDH’s can be presented as [MII 12x MIII x (OH)2 ]X1 [An2 X/n ? mH2 O]X2 , where An2 is as exchangeable anion. LDH’s are extensively studied not only as anion exchangeable compounds but also as functional materials.6 Recently, HDS has attracted much interest as an anion-exchangeable compound because of its lamellar structure. The general formula of HDS’s is [MII 12x , M0II 11x ) (OH)3(12y) ]1 An2 (113y)/n mH2 O in which M and M0 correspond to divalent metals such as Cu, Co, Ni, Mg, Zn, Cd, Fe, and Mn. An2 is an anion situated between the cation layers of [(MII 12x , M0II 11x ) (OH)3(12y) ]1 , and can be either monovalent, Cl2 , No3 2 , Br2 , ClO4 2 , MnO4 2 , and NO2 2 , or divalent, SO4 22 and CO3 22 . In this study, we have prepared a new zinc hydroxide double salt exchanged with an organic anion. The structure of zinc hydroxide nitrate8,9 can be regarded as a variation of hypothetical Zn(OH)2 structure in the C6 or CdI2 -type group. One quarter of the zinc atoms are removed from the octahedral interstices of the sheet. Each occupied octahedron shares its edges with two unoccupied and four occupied octahedral. The resulting sheet is negatively charged: [Zn3 oct (OH)8 ]22 . Tetrahedrally coordinated zinc atoms are located above and below the empty octahedron. Three corners of the tetrahedron are occupied by hydroxide ions belonging to the sheet described above, the fourth by a water 848
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J. Mater. Res., Vol. 13, No. 4, Apr 1998
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molecule. The complex sheet so formed is positively charged, [Zn3 oct (OH)8 Zn2 tetr (H2 O)2 ]21 . II. EXPERIMENTAL
The parent compound, Zn5 (OH)8 (NO3 )2 ? 2H2 O (
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