直接脱碳酸化制备有机离子插层的层状双氢氧化物

层状双氢氧化物(Layered double hydroxide, LDH)是一种具有阴离子可交换性质的层状无机材料, 由于其具有多种功能性质, 已被广泛应用于催化^[1~3]、酸吸附剂^[4]、传感器^[5]及聚合物填料^[6~8]等领域. 传统的共沉淀法制备的LDH结晶度低、尺寸小(直径通常小于100 nm). 1998年, Costantino等^[9]采用均匀沉淀法制备出了高结晶度、大尺寸(微米量级)且层间具有CO₃^2-的LDH(LDH-CO₃), 引起了人们的极大兴趣. 为解决LDH-CO₃难于交换和剥离的难题, Iyi等^[10,11]采用两步法制备了层间具有NO₃^- 或有机阴离子的LDH, 即首先采用 HCl-NaCl混合溶液将LDH-CO₃转化成为LDH-Cl, 然后再采用过量的阴离子进行交换制备LDH-NO₃或有机阴离子插层的LDH.     

微波辅助ZnFe-LDHs的合成及其异戊烯氧化脱氢性能的研究

以微波辅助合成系列ZnFe-LDHs并用于异戊烯氧化脱氢,借助其表面易于羟基化的性质降低水烯比。结果表明,微波法可明显缩短合成时间,在微波功率为600W、微波温度为95℃和微波时间为1h的条件下可获得结晶度和纯度较高的ZnFe-LDHs。与传统法相比,以其为前驱体获得的催化剂在异戊烯氧化脱氢中表现出更高的活性和选择性,水烯比为5.7时,异戊二烯收率达到52%,选择性达83%,明显降低了水烯比。     

镁铝水滑石的有机改性实验研究

采用共沉淀法合成了对甲基苯磺酸有机插层改性的镁铝水滑石,用XRD、FTIR、TG-DSC等技术表征产物特征.研究表明,合成的对甲基苯磺酸插层LDH物相纯净、结晶度高,层间无硝酸根,而且2:1型有更好的晶形;2:1型对甲基苯磺酸插层LDH在450-500℃层状结构逐渐被破坏,而3:1型在400-460℃0层状结构被破坏....     

Fe/膨胀石墨插层复合物的简易制备与电磁特性研究

以膨胀石墨和硫酸亚铁为前驱物,采用一步还原法得到Fe/膨胀石墨(Fe/EG)插层复合物.并用SEM、XRD、网络矢量分析仪等测试仪器分别研究了Fe含量(wFe)对Fe/EG插层复合物的形貌、结构、微波电磁和吸波性能的影响.结果表明:改变插层剂Fe的含量能有效地调控Fe/EG插层复合物的微波电磁与吸收特性.随wFe在27.5wt%～71.5wt%范围内增大,Fe/EG插层复合物的介电常数在wFe=27.5wt%时达到最大值,磁导率呈现多重共振现象,微波吸收性能逐渐增强.这种优异的微波吸收特性归功于Fe/EG插层复合物增强的电磁匹配和磁共振损耗.     

偏氯乙烯共聚物/层状双金属氢氧化物纳米复合材料的制备与表征

通过硝酸根插层层状双金属氢氧化物(LDH)与可逆加成-断裂链转移(RAFT)试剂S,S’-对(α,α’-二甲基-α″-乙酸)三硫代碳酸酯(CTA)阴离子的离子交换制备CTA阴离子插层LDH,再通过原位RAFT活性自由基聚合制备偏氯乙烯-丙烯酸甲酯(VDC-MA)共聚物/LDH纳米复合材料.采用傅里叶变换红外光谱、元素分析和X-射线衍射、透射电子显微镜、凝胶渗透色谱仪和热失重仪表征了CTA阴离子插层LDH和纳米复合材料的结构和性能.结果表明,CTA阴离子可以置换硝酸根阴离子插入到LDH层间,LDH层间距由0.89 nm增大到1.50 nm;在原位RAFT聚合过程中,LDH逐渐剥离,LDH以纳米层板形式分散在VDC-MA共聚物基体中;VDC-MA共聚物数均分子量随加入的插层CTA阴离子含量增加而减小,聚合具有活性特征.此外,含量LDH的引入可明显提高VDC-MA共聚物的热稳定性.     

2-羟基-4-甲氧基二苯甲酮-5-磺酸插层水滑石的制备及性能(英文)

以层状镁铝双金属氢氧化物(MgAlLayeredDoubleHydroxides,Mg-AlLDHs)为主体,以有机紫外光稳定剂2-羟基-4-甲氧基二苯甲酮-5-磺酸(BP)为客体,结合焙烧复原法和阴离子交换法合成了具有超分子结构有机-无机插层复合物(MgAl-BPLDHs),研究了层间阴离子、反应介质、pH值、反应时间等因素对于插层材料超分子结构的影响。用FTIR、XRD、TG-DTA、UV-Vis和粒度分析对其不同尺度的结构、热稳定性和紫外光稳定性等进行表征。结果表明,采用阴离子交换法难以进行插层反应;通过焙烧复原法可显著降低MgAl-LDHs层间CO2-离子,从而有利于BP阴离子交换进入MgAl-LDHs层间,在去离子水中,水温100℃,pH=7,反应时间为48h,BP过饱和的条件下合成得到最高插层率的MgAl-BP-LDHs;主体水滑石层板与客体以静电力和氢键相互作用,得到的超分子结构材料具有良好的热稳定及兼具优异的紫外屏蔽、吸收性能,是一种新型的有机-无机复合光热稳定剂。     

2-羟基-4-甲氧基二苯甲酮-5-磺酸插层水滑石的制备及性能

以层状镁铝双金属氢氧化物（MgAl Layered Double Hydroxides,Mg-Al LDHs）为主体,以有机紫外光稳定剂2-羟基-4-甲氧基二苯甲酮-5-磺酸（BP）为客体,结合焙烧复原法和阴离子交换法合成了具有超分子结构有机-无机插层复合物（MgAl-BP-LDHs）,研究了层间阴离子、反应介质、pH值、反应时间等因素对于插层材料超分子结构的影响。用FTIR、XRD、TG-DTA、UV-Vis和粒度分析对其不同尺度的结构、热稳定性和紫外光稳定性等进行表征。结果表明,采用阴离子交换法难以进行插层反应;通过焙烧复原法可显著降低MgAl-LDHs层间CO₂^-离子,从而有利于BP阴离子交换进入MgAl-LDHs层间,在去离子水中,水温100℃,pH=7,反应时间为48 h,BP过饱和的条件下合成得到最高插层率的MgAl-BP-LDHs;主体水滑石层板与客体以静电力和氢键相互作用,得到的超分子结构材料具有良好的热稳定及兼具优异的紫外屏蔽、吸收性能,是一种新型的有机-无机复合光热稳定剂。     

10-羟基喜树碱-癸二酸-LDH杂化物的制备及性能

采用二次插层法成功制备了10-羟基喜树碱(HCPT)-癸二酸(SC)插层的层状双金属氢氧化物(LDH). 先采用共沉淀法制备SC柱撑LDH杂化物(SC-LDH), 再在乙醇介质中将HCPT插入LDH层间形成HCPT-SC-LDH纳米杂化物. 依据SC和HCPT的分子尺寸和纳米杂化物的通道高度, 推测SC分子在层间可能为双层排列, SC分子两端的羧基同时键合在同一个LDH层片表面上; HCPT分子插入(或溶入)SC分子碳氢链形成的疏水区中. 所制备的纳米杂化物既可稳定HCPT的内酯环, 又可明显提高HCPT的溶解度, 还具有明显的药物缓释效果, 其释放动力学过程符合准二级动力学方程.     

微波辅助溶剂热法合成烟酸锌配位聚合物

首次利用微波辅助溶剂热法,10min便成功地合成了烟酸锌配位聚合物并对其性质进行了表征。讨论了时间、温度、底物浓度、加热方法及溶剂等因素对产物结晶情况和晶体粒径大小的影响;将微波溶剂热与传统溶剂热法相结合,得到的产物既具备了微波加热反应速度快、晶体成核均匀等优点,同时也得到了较大的单晶体并对其进行了晶体结构解析。     

层状双金属氢氧化物的控制合成及其在水处理中的应用

层状双金属氢氧化物(LDH)作为无机层状粒子的典型代表,已在众多应用领域展现出巨大潜力。然而,目前的研究大多从LDH的层板组成、层间阴离子种类以及粒子尺寸的角度入手对其进行功能优化,较少关注形貌结构对LDH性能的影响。本文从简要介绍LDH的基本结构和性质出发,详细总结了常规六方片状以及特殊形貌(球状、多面体状、纳米线状、环状等)LDH的制备方法。结合LDH与其他功能粒子复合以提升其综合性能的需求,深入分析了反应配方、合成条件以及基体表面性质对LDH复合材料形貌的调控规律,并综述LDH及其复合物分别作为吸附、催化和分离材料在水处理中的应用。最后,对当前控制合成LDH所存在的难点及其未来研究方向进行了展望。     

Benzocarbazole anions intercalated layered double hydroxide and its tunable fluorescence

Luminescent benzocarbazole anions (BCZC) intercalated into the interlayer region of Mg-Al-layered double hydroxides (BCZC/LDH) with different layered charge densities (LCD) were prepared. The structure and chemical composition of the composites were characterized by X-ray diffraction, elemental analysis, thermogravimetry and differential thermal analysis (TG-DTA), infrared spectra (FT-IR), UV-vis absorption and fluorescence spectroscopy. The photoemission behavior of BCZC in the LDH matrix with high (Mg/Al ratio = 1.801) and low (Mg/Al ratio = 3.132) LCD is similar to that of BCZC solid and aqueous solution states respectively, indicating that the luminescence performances of the intercalated dye anions can be tuned by adjusting the LCD of the LDH layer. Moreover, the thermal stability and stacking order of BCZC are largely improved upon intercalation, and the BCZC/LDH thin film exhibits well polarized luminescence with the luminescent anisotropy of 0.15-0.20. In addition, molecular dynamics (MD) simulation was employed to calculate the basal spacing and molecular arrangement of the intercalated BCZC within the LDH matrix. The simulation results show that the distribution of BCZC anions is much broader in the gallery of Mg-Al-LDH with high LCD, while BCZC anions exhibit a more ordered arrangement in LDH with low LCD. Furthermore, the radial distribution functions of interlayer water molecules were also studied. Based on the combination of experiment and theoretical simulation, this work provides a detailed understanding of the tunable photoluminescence, orientation and diffusion behavior of the luminescent molecules confined within the gallery of a 2D inorganic matrix.     

Application of simplified version of advanced isoconversional procedure in non-isothermal kinetic study

Thermogravimetric analysis (TG) and powder X-ray diffraction (PXRD) were used to study some selected Mg/Al and Zn/Al layered double hydroxides (LDHs) prepared by co-precipitation. A Mg/Al hydrotalcite was investigated before and after reformation in fluoride and nitrate solutions. Little change in the TG or PXRD patterns was observed. It was proposed that successful intercalation of nitrate anions has occurred. However, the absence of any change in the d ₍₀₀₃₎ interlayer spacing suggests that fluoride anions were not intercalated between the LDH layers. Any fluoride anions that were removed from solution are most likely adsorbed onto the outer surfaces of the hydrotalcite. As fluoride removal was not quantified it is not possible to confirm that this has happened without further experimentation. Carbonate is probably intercalated into the interlayer of these hydrotalcites, as well as fluoride or nitrate. The carbonate most likely originates from either incomplete decarbonation during thermal activation or adsorption from the atmosphere or dissolved in the deionised water. Small and large scale co-precipitation syntheses of a Zn/Al LDH were also investigated to determine if there was any change in the product. While the small scale experiment produced a good quality LDH of reasonable purity; the large scale synthesis resulted in several additional phases. Imprecise measurement and difficulty in handling the large quantities of reagents appeared to be sufficient to alter the reaction conditions causing a mixture of phases to be formed.     

Preparation and characterization of a new layered double hydroxide, Co-Zr-Si

The layered double hydroxides (LDHs) are nano-ordered layered compounds and well known for their ability to intercalate anionic compounds. Most LDH is prepared conventionally only with divalent and trivalent cations. In this study, Co-Zr-Si LDH, consisting of divalent, tetravalent, and tetravalent cations, was prepared and reacted with monocarboxylic acids at room temperature. The Co-Zr-Si LDH and intercalated compounds have been characterized by energy-dispersive X-ray spectrometry, X-ray powder diffraction, IR spectra, thermal analysis, and scanning electron microscopy (SEM). The insertion of cyanate and carbonate anions into LDH was confirmed by IR spectra. XRD patterns of the prepared Co-Zr-Si LDH showed that the interlayer spacing of the LDH is 0.78 nm. The spacing is similar to that of usual LDH in which chloride, carbonate, or bromide anion is the guest. SEM images showed that Co-Zr-Si LDH can exist as plate-like or fibrous structures.     

Layered double hydroxide/polyethylene terephthalate nanocomposites. Influence of the intercalated LDH anion and the type of polymerization heating method

Conventional and microwave heating routes have been used to prepare PET–LDH (polyethylene terephthalate–layered double hydroxide) composites with 1–10 wt% LDH by in situ polymerization. To enhance the compatibility between PET and the LDH, terephthalate or dodecyl sulphate had been previously intercalated in the LDH. PXRD and TEM were used to detect the degree of dispersion of the filler and the type of the polymeric composites obtained, and FTIR spectroscopy confirmed that the polymerization process had taken place. The thermal stability of these composites, as studied by thermogravimetric analysis, was enhanced when the microwave heating method was applied. Dodecyl sulphate was more effective than terephthalate to exfoliate the samples, which only occurred for the terephthalate ones under microwave irradiation.     

Synthesis and characterization of 10-hydroxycamptothecin – sebacate – layered double hydroxide nanocomposites

10-Hydroxycamptothecin (HCPT) as a hydrophobic anticancer drug brings many challenges in the clinical applications due to its poor water solubility and the presence of a chemically unstable lactone ring. In this work, the nanocomposites of HCPT intercalated layered double hydroxide (LDH) were prepared by a secondary intercalation method, and the encapsulated HCPT could keep the biologically active lactone form. A Zn–Al–NO₃ LDH was pillared with sebacate anions by a co-precipitation method in an aqueous medium, and then HCPT was intercalated into the LDH's gallery via hydrophobic interaction in an ethanol medium. The parallel alkyl chains of perpendicularly arranged sebacate anions in the LDH gallery provide a hydrophobic space for the drug intercalation. The in vitro release kinetics of HCPT from the nanocomposites could be fitted with the pseudo-second-order kinetic model, and the diffusion of HCPT through the LDH particles played an important role in controlling the drug release. The nanocomposites can be considered as a potential drug delivery system.     

Preparation of Mg–Al layered double hydroxides intercalated with alkyl sulfates and investigation of their capacity to take up N,N-dimethylaniline from aqueous solutions

This study examined the effect of the interlayer spacing of a Mg–Al layered double hydroxide (Mg–Al LDH) on the ability of the Mg–Al LDH to take up a nonionic organic material. Mg–Al LDHs, intercalated with 1-propanesulfonate (PS^?), 1-hexanesulfonate (HS^?), and 1-dodecanesulfonate (DS^?), were prepared by coprecipitation, yielding PS·Mg–Al LDH, HS·Mg–Al LDH, and DS·Mg–Al LDH, respectively. The increase in the alkyl chain lengths of the Mg–Al LDHs (PS^? < HS^? < DS^?) resulted in the perpendicular orientation of the organic acid anions in the interlayer of Mg–Al LDH, which in turn resulted in more organic acid anions being accommodated in the interlayer space. An organic acid anion with a large molecular length was more easily intercalated in the interlayer of Mg–Al LDH than one with a small molecular length. This was attributed to the hydrophobic interaction between the alkyl chains, affecting the intercalation of the organic acid anions. The uptake of N,N-dimethylaniline (DMA) by Mg–Al LDHs increased in the order PS·Mg–Al LDH < HS·Mg–Al LDH < DS·Mg–Al LDH. The uptake was attributed to the hydrophobic interactions between DMA and the intercalated PS^?, HS^?, and DS^?. Thus, Mg–Al LDH, which has a lot of large interlayer spacings when intercalated with organic acid anions, can take up a large number of DMA molecules from an aqueous solution.     

Intercalation behavior of amino acids into Zn-Al-layered double hydroxide by calcination-rehydration reaction

The intercalation of amino acids for the Zn-Al-layered double hydroxide (LDH) has been investigated by the calcination-rehydration reaction at 298 K using mainly phenylalanine (Phe) as a guest amino acid. The Zn-Al oxide precursor prepared by the calcination of Zn-Al-carbonated LDH at 773 K for 2 h was used as the host material. The amount of Phe intercalated by the rehydration was remarkably influenced by the initial solution pH and reached ca. 2.7 times for anion exchange capacity (AEC) of the LDH at neutral and weak alkaline solutions, suggesting that Phe was intercalated as amphoteric ion form into the LDH interlayer. As Phe is intercalated for the LDH as monovalent anion in alkaline solution, the amount of Phe intercalated at pH 10.5 corresponded with AEC of the LDH. The solid products were found to have the expanded LDH structure, which confirmed that Phe was intercalated into the LDH interlayer as amphoteric ion or anion form. The basal spacing, d₀₀₃, of the Phe/LDH was 1.58 nm at pH 7.0 and 0.80 nm at pH 10.5; two kinds of expansion suggested for Phe in the interlayer space as vertical (pH 7.0) and horizontal (pH 10.5) orientations. The intercalation behavior of various amino acids for the LDH was also found to be greatly influenced by the feature of the amino acid side-chain, namely, its carbon-chain length, structure and physicochemical property. In particular, α-amino acids possessing a hydrophobic or negative-charged side-chain were preferentially intercalated for the LDH.     

On the intercalation of the iodine-iodide couple on layered double hydroxides with different particle sizes

Molecular iodine was intercalated from nonaqueous solution into microsized ZnAl-layered double hydroxide (LDH) in the iodide form, generating the I(3)(-)/I(-) redox couple into the interlayer region. Chloroform, ethanol, acetonitrile, or diethyl ether were used as solvents to dissolve the molecular iodine. The intercalation compounds were characterized by thermogravimetric analysis, X-ray powder diffraction, UV-vis spectroscopy, and scanning and transmission electron microscopy. The stability of iodine-solvent adducts and the iodine concentration affected the LDH iodine loading, and samples with I(2)/I(-) molar ratio ranging from 0.14 to 0.82 were prepared. Nanosized, well dispersible LDH, synthesized by the urea method in water-ethylene glycol media, were also prepared and successfully functionalized with the I(3)(-)/I(-) redox couple applying the conditions optimized for the micrometric systems.     

Characterization of self-assembled films of NiGa layered double hydroxide nanosheets and their electrochemical properties

In this study, we have demonstrated the synthesis and delamination of a rarely studied NiGa layered double hydroxide (LDH) system. Hydrothermal treatment under agitation conditions at 200 °C for 4 h resulted in the formation of highly crystalline NiGa LDHs in a shorter time than those synthesized without agitation. The LDH was delaminated into the individual nanosheets in formamide. The most significant finding in this study is the electrochemical behavior of interlayer ferricyanide anions intercalated with the layer-by-layer (LBL) assembly method. The morphology of LBL film with one layer is also monitored with atomic force microscopy. The cyclic voltammogram is similar to potassium metal hexacyanoferrate systems with its unique two-peak wave. Raman spectrum of the film revealed that the metal center of the interlayer cyano complex is in interaction with the Ni²⁺ of the host layer. It was concluded that the two-peak cyclic voltammogram of the film is a result of two different forms of the hexacyanoferrate in the interlayer.     

熔融插层法制备LLDPE/MgAl-LDH 剥离型纳米复合材料及其热性能研究

The interlayer surface of MgAl layered double hydroxide （MgAl-LDH） was modified by exchanging about half of the interlayer nitrate anions by dodecyl sulfate anions （DS） to get MgAl（H-DS） LDH, and then the MgAl（H-DS） was melt intercalated by LLDPE to get the LLDPE/MgAl-LDH exfoliation nanocomposites. The samples were characterized by Fourier transform infrared （PTIR） spectroscopy, X-ray diffraction （XRD）, ion chromatography, transmission electron microscopy （TEM）, and thermogravimetry analysis （TGA）. The nanoscale dispersion of MgAl-LDH layers in the LLDPE matrix was verified by the disappearance of （001） XRD reflection of the modified MgAl-LDH and by the TEM observation. The TGA profiles of LLDPE/MgAl-LDH nanocomposites show a faster charring process between 210 and 370 ℃ and a higher thermal stability above 370 ℃than LLDPE. The decomposition temperature of the nanocomposites with 10 wt% MgAl（H-DS） can be 42 ℃ higher than that of LLDPE at 40% weight loss.