Abstract:Mol. L'rur. m d Liy.The ordered layered double hydroxide, [LiAI,(OH),]C1.2H20 exhibits shape-selective ion-exchange intercalation of dicarboxylate anions. Specific isomeric preferences can he controlled by varying the reaction temperatures. The intercalated guests can be quantitatively recovered from the host lattice with concomitant regeneration of the host offering a novel approach in separation science. To illustrate the potential of this new material in separation science. we describe the isolation of pure… Show more
“…Li-Al LDHs have been shown to be efficient candidates for the selective intercalation of various organic anions [19][20][21]. Compared to LDHs, there is limited knowledge on the interlayer chemistry, and competitive intercalation properties of LHSs save for a few reports in recent times.…”
“…Li-Al LDHs have been shown to be efficient candidates for the selective intercalation of various organic anions [19][20][21]. Compared to LDHs, there is limited knowledge on the interlayer chemistry, and competitive intercalation properties of LHSs save for a few reports in recent times.…”
“…We have already exploited time-resolved in situ diffraction methods to study a variety of intercalation reactions. [12][13][14][15][16][17][18][19] Time-resolved, in situ energy-dispersive X-ray diffraction (EDXRD) is particularly suitable for the study of these reactions because the simultaneous observation of a wide range of d spacings is possible. An energydiscriminating detector is positioned at a fixed angle to a white synchrotron X-ray beam, and the full spectral width of the beam is used to record diffraction peaks; hence, the Bragg reflections are separated by their energies.…”
Section: Introductionmentioning
confidence: 99%
“…Second, in situ experiments allow reactions to be continuously monitored, and a much greater amount of data can be collected. We have already exploited time-resolved in situ diffraction methods to study a variety of intercalation reactions. − 1 Experimental apparatus used to perform time-resolved in situ EDXRD experiments.…”
Intercalation of a range of phosphonic acids into [LiAl 2 (OH) 6 ]Cl‚H 2 O at pH 8 leads to cointercalation of both mono-and dianionic guest anions. Solid-state 31 P NMR data can be used to show that these materials exhibit a 31 P chemical shift that is intermediate between the values for the monoanionic and dianionic forms of the respective acids, suggesting that rapid proton exchange occurs between the intercalated anions. It is possible to calculate the relative amounts of mono-and dianionic species present using the observed averaged chemical shift of the intercalate phase. In the case of methylphosphonic acid, the ratio of mono-and dianionic species (MePO 3 H -/MePO 3 2-) is estimated to be 2.1. The intercalation of methyl-, ethyl-, phenyl-, and benzylphosphonic acids into [LiAl 2 (OH) 6 ]Cl‚H 2 O was studied using time-resolved, in situ energy-dispersive synchrotron X-ray diffraction. The rates of intercalation are significantly greater for methylphosphonic acid (MPA), ethylphosphonic acid (EPA), and benzylphosphonic acid (BPA) than for phenylphosphonic acid (PPA). The large BPA anions intercalate the most quickly, and MPA reacts more rapidly than EPA. Kinetic analyses of the rate data suggest that these are diffusion-controlled reactions. In situ X-ray diffraction experiments performed with slow addition of the guest have allowed observation of intermediate crystalline phases during the reactions with MPA and BPA. The intermediate phases can be indexed assuming a second-stage intercalation compound in which alternate interlayer regions are occupied by phosphonic acid and Clanions, respectively (Williams et al. Chem. Commun. 2003, 1816. The observation of these secondstage intermediates is very surprising, because staging in rigid layer lattices such as layered double hydroxides (LDHs) is highly unusual.
“…However, what has been interesting to us is that the anion exchange reactions have a high degree of selectivity, which can be used as novel separation chemistry, especially for separation of isomeric anions [11,13]. In this paper, we are trying to demonstrate that this selective anion exchange chemistry can also be used to control chemical reactions, the idea is as follows [ It is a well-known fact that there are anionic reactants, products, byproducts, or intermediates in many of the known reactions.…”
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