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Synthesis and Characterization of Methanesulfonate and Ethanesulfonate Intercalated Lithium Aluminum LDHs

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Document pages: 13 pages

Abstract: LDH-phases become increasingly interesting due to their broad ability tobe able to incorporate many different cations and anions. The intercalation of methanesulfonateand ethanesulfonate into a Li-LDH as well as the behavior of the interlayerstructure as a function of the temperature is presented. A hexagonal P63 m[LiAl2(OH)6][Cl∙1.5H2O] (Li-Al-Cl) precursor LDH wassynthesized by hydrothermal treating of a LiCl solution with γ-Al(OH)3. This precursor wasused to intercalate methanesulfonate (CH3O3S−)and ethanesulfonate (C2H5O3S−)through anion exchange by stirring Li-Al-Cl in a solution of the respectiveorganic Li-salt (90˚C, 12 h). X-ray diffraction pattern showed anincrease of the interlayer space c (d001) of Li-Al-methanesulfonate(Li-Al-MS) with 1.2886 nm and Li-Al-ethanesulfonate (Li-Al-ES) with 1.3816 nmcompared to the precursor with 0.7630 nm. Further investigations withFourier-transform infrared spectroscopy and scanning electron microscopyconfirmed a complete anion exchange of the organic molecules with the precursorCl−. Both synthesized LDH compounds [LiAl2(OH)6]CH3SO3∙nH2O(n = 2.24-3.72 (Li-Al-MS) and [LiAl2(OH)6]C2H5SO3}∙nH2O(n = 1.5) (Li-Al-ES) showed a monomolecular interlayer structure withadditional interlayer water at room temperature. By increasing the temperature,the interlayer water was removed and the interlayer space c of Li-Al-MS decreased to 0.87735 nm (at 55˚C).Calculations showed that a slight displacement of the organic molecules isnecessary to achieve this interlayer space. Different behavior of Li-Al-EScould be observed during thermal treatment. Two phases coexisted at 75˚C - 85˚C, one with a reduced c (0.9015 nm, 75˚C) and one with increased c (1.5643 nm, 85˚C) compared to the LDHcompound at room temperature. The increase of c is due to the formation of a bimolecular interlayerstructure.

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