Staging of Organic and Inorganic Anions in Layered Double Hydroxides

Abstract

The layered double hydroxides (LDHs) Zn2Al(OH)6Cl·nH2O, Zn2Cr(OH)6Cl·nH2O, and Cu2Cr(OH)6Cl·nH2O have been shown to undergo staged intercalation reactions with succinate and tartrate anions. Monitoring the process in situ using energy-dispersive X-ray diffraction reveals the formation of second-stage intermediates caused by the filling of every second layer. Depending on the nature of the organic anion, the Bragg peaks of the second-stage intermediates and the fully organic exchanged materials emerge in two distinct sequences indicating two exchange pathways. For tartrate exchange, the fully exchanged material is not observed until the intermediate has gone through its maximum and the chloride precursor has disappeared completely, while for succinate exchange, the final state of intercalation and the second-stage intermediate simultaneously appear. Similar staging has previously been reported only for LiAl2(OH)6Cl·2H2O. These results demonstrate that staging in the intercalation of LDH does not involve a structural order of the host and cannot be explained by a tactoid mechanism.

Co‐Assembly of LDH Nanosheets with Crown Ethers: Structural Transformation and Water‐Adsorption Behavior

“…[ 26c,26e] There have been suggestions that staging occurs as a result of a hydrophobic/hydrophilic separation, [37] which is consistent with the present case. This would also explain why staging occurs only in the presence of organic anions.…”

A Family of Visible‐Light Responsive Photocatalysts Obtained by Dispersing CrO6 Octahedra into a Hydrotalcite Matrix

“…In each case, the reflections can be indexed to a hexagonal lattice with R3 m rhombohedral symmetry, commonly used for the description of LDH structures. [22] The basal spacings of CuCr, NiCr and ZnCrÀNO 3 -LDH were 0.888, 0.881 and 0.867 nm, respectively, close to the value of NO 3 À -containing LDH; the basal spacings of CuCr, NiCr, ZnCr À CO 3 -LDH were 0.735, 0.791 and 0.751 nm, respectively; this is consistent with the CO 3 2À -type LDH. Moreover, the FT-IR spectra ( Figure S1 in the Supporting Information) of these M II Cr-LDHs (M = Cu, Ni, Zn) also provide evidence for the presence of NO 3 À (at 1384 cm À1 ) and CO 3 2À (at 1370 cm À1 ), respectively.…”

Preferential adsorption of 2,4-dichlorophenoxyacetate from associated binary-solute aqueous systems by Mg/Al-NO3 layered double hydroxides with different nitrate orientations

“…Line-width broadening may also cause difficulty in detecting some reflections of the 2,4-D-containing phase. As suggested by Pisson et al [35] and Taviot-Gueho et al [36], this intermediate phase may occur as a result of hydrophobic/hydrophilic separation, and nitrate and 2,4-D may tend to occupy different interlayers. The layers containing nitrate and 2,4-D then form a randomly interstratified phase, so that a set of the (0 0 l) reflections of the 2,4-D phase did not appear due to the Hendricks-Teller effect [37,38].…”