Intercalation of Macrocyclic Crown Ether into Well-Crystallized LDH: Formation of Staging Structure and Secondary Host−Guest Reaction

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• 作者：Shulan Ma ; Cuihong Fan ; Li Du ; Gailing Huang ; Xiaojing Yang ; Weiping Tang ; Yoji Makita ; Kenta Ooi
• 刊名：Chemistry of Materials
• 出版年：2009
• 出版时间：August 11, 2009
• 年：2009
• 卷：21
• 期：15
• 页码：3602-3610
• 全文大小：862K
• 年卷期：v.21,no.15(August 11, 2009)
• ISSN：1520-5002

文摘

A carboxyethyl substituted azacrown ether derivative (CSAE) was intercalated as a second host into a parent host of well-crystallized crystal of Mg−Al layered double hydroxide (MgAl-LDH) by a CSAE/NO₃⁻ ion-exchange reaction. The influence of intercalation temperature on the structures and compositions of CSAE−LDH nanocomposites was investigated. The composites obtained at the temperatures below 70 °C had almost the same CASE contents and layered structures with a basal spacing of about 1.6 nm, corresponding to the vertical orientation of CSAE plane to the LDH layer. The chemical analysis showed that a considerable amount of CO₃²⁻ (with CO₃²⁻/CSAE molar ratio of 1.4) was incorporated in the interlayer of LDH. The CSAE content decreased while CO₃²⁻ content increased with an increase of the intercalation temperature in the region above 70 °C. At 100 °C, a second staging phase of 2.33 nm appeared, attributed to the ordered stacking of the 1.6 nm phase and a 0.77 nm phase produced by the CO₃²⁻/CSAE exchange. At higher temperatures, a new phase with a basal spacing of 1.18 nm appeared, which corresponds to the tilt/twisted orientation of CSAE anions in the interlayer. The other second staging phase of 2.08 nm appeared obviously at 150 °C, due to the regular stacking of the 1.18 and 0.77 nm phases. The adsorptive properties for transition metal ions were studied using the 70 and 150 °C reacted composites. The 70 °C reacted one showed higher adsorptivity toward transition metal ions; the adsorptive capacity increased in the sequence of Cu²⁺ > Ni²⁺ > Co²⁺ > Zn²⁺, and distribution coefficient for Cu²⁺ was markedly higher than those for the other ions. However, the 150 °C reacted one showed little adsorptivity toward these ions. The adsorption for transition metal ions was accompanied by the intercalation of nearly equivalent amount of nitrate ions. This shows that the interlayer CSAE ions in the 1.6 nm phase act as a second host, but those in the 1.18 nm phase do not.