Synthesis and properties of pyrazine-pillared Ag3Mo2O4F7 and AgReO4 layered phases

The new pyrazine-pillared solids, AgReO₄(C₄H₄N₂) (I) and Ag₃Mo₂O₄F₇(C₄H₄N₂)₃ (C₄H₄N₂=pyrazine, pyz) (II), were synthesized by hydrothermal methods at 150 °C and characterized using single crystal X-ray diffraction (I—P2₁/c, No. 14, Z=4, a=7.2238(6) Å, b=7.4940(7) Å, c=15.451(1) Å, β=92.296(4)°; II—P2/n, No. 13, Z=2, a=7.6465(9) Å, b=7.1888(5) Å, c=19.142(2) Å, β=100.284(8)°), thermogravimetric analysis, UV-Vis diffuse reflectance, and photoluminescence measurements. Individual Ag(pyz) chains in I are bonded to three perrhenate ReO₄^- tetrahedra per layer, while each layer in II contains sets of three edge-shared Ag(pyz) chains (π-π stacked) that are edge-shared to four Mo₂O₄F₇^3- dimers. A relatively small interlayer spacing results from the short length of the pyrazine pillars, and which can be removed at just slightly above their preparation temperature, at >150-175 °C, to produce crystalline AgReO₄ for I, and Ag₂MoO₄ and an unidentified product for II. Both pillared solids exhibit strong orange-yellow photoemission, at 575 nm for I and 560 nm for II, arising from electronic excitations across (charge transfer) band gaps of 2.91 and 2.76 eV in each, respectively. Their structures and properties are analyzed with respect to parent ‘organic free’ silver perrhenate and molybdate solids which manifest similar photoemissions, as well as to the calculated electronic band structures.     

Facile Synthesis of Al-pillared Mesoporous Montmorillonite Assisted with Concentrated Al13 Solution

Al-pillared mesoporous montmorillonite was facilely synthesized from concentrated Al13 solution obtained by vacuum concentrating-ultrasonic pillaring strategy.Concentrated Al13 solution could reduce the process of pillare and increase pillaring efficiency.The absolute value of layer distance could be increased by 0.96 nm via concentrated Al13 solution pillare.27Al NMR indicates that Al Keggin ions of concentrated Al13 are arranged in a more regular way by vacuum concentrating method.The Al-pillared mesoporous montmorillonite from concentrated Al13 solution has bigger specific surface area and even pore size distribution which were characterized by X-ray diffraction（XRD） and nitrogen adsorption measurement.Furthermore the catalytic activity of Ai-pillared montmorillonite loaded Ni and Mo catalysts was tested by the hydrodesulfurization of thiophene.The thiophene conversion reached 77.5％,which was higher than the corresponding value reported in the literature.     

Kinetics of 2‐Propanol Dehydration over Montmorillonite Clays and Pillared Montmorillonites

Metal ion exchanged montmorillonites (AlM & CrM) and metal oxide pillared montmorillonite (AlPM & CrPM) were prepared and characterized with XRD, FT‐IR, nitrogen adsorption and TPD of ammonia. The pillaring process results in a remarkable increase of interlayer distance, surface area and acid amount of the catalyst. However, increasing the calcined temperature causes reverse effects for the CrPM catalyst. The acid amount decreases in the order of CrPM200 < CrPM300 < AlPM500 < CrM < CrPM400 ≥ CrPM500 ≥ AlM. In the dehydration of 2‐propanol to propene, the reaction follows first order kinetics and the apparent rate constant is related to the catalyst acid amount. Compensation effect occurs in this reaction over the series of catalysts.     

杂多阴离子柱撑水滑石层柱相互作用的光电子能谱研究

本文用Ｘ－光电子能谱仪对二十二种同多和杂多阴离子柱撑水滑石层和柱中元素电子结合能的化学位移进行了研究。同时通过ＩＲ，ＸＲＤ的分析，对ＸＰＳ结果的讨论提供了一定的补充，探讨了同层不同柱，同性不同层的ＰＯＭ－ＬＤＨＳ的层柱相互作用机理。     

Cationic versus Anionic Pillared Layered Substrates: Comparison of the Pillaring Reactions and the Resulting Porosities

Cationic clays and Layered Double Hydroxides (LDHs) are both layeredion exchangers, in which a stable (micro)porosity can be induced via apillaring process. For the cationic clays, the [Zr]-pillaring of hectoritecreates a broad micropore distribution with the maximum at 1.42–2.12nm. The [Al]-equivalent exhibits a narrower distribution, with pores between0.71 and 1.06 nm being dominant. In case of the [Zr]-pillared form a surfacearea of 294 m²/g and a micropore volume of 0.118cm³/g have been obtained. The same reaction on the syntheticlaponite clay reveals a much higher surface area (606 m²/g)and porosity (µPV = 0.336 cm³/g). Forlaponite, extra pores are created in the supermicropore-small mesoporeregion due to the preferential edge-to-face and edge-to-edge stacking of itssmaller sized clay layers.For the pillaring of MgAl- and ZnAl-LDHs with polyoxometalates (POMs),using large organic anions for pre-swelling purposes forms the mostpromising method for the creation of stable pores. It avoids the formationof sidephases, and gives rise to medium(-high) µPVs. Charge density onthe layers forms the key factor, lowering it improves the porositycharacteristics significantly. [Fe(CN)₆]-MgAl-LDHs exhibitmore spectacular properties, with surface areas and µPVs exceedingthose of pillared hectorite. A variation in the charge density via theM ^II/M ^III ratio optimizes theporosity properties. A M ^II/M ^IIIratio of 3.33 results in a SA of 499 m²/g and a µPV of0.177 cc/g. For LDHs, both types of pillars create mainly small micropores,with a diameter smaller than 0.71 nm.     

硼酸根插层水滑石层间组成及取向结构的控制

以Mg0 .67Al0 .3 3 (OH) 2 (CO3 ) 0 .165·0 .62H2 OLDHs为前体 ,以水为分散介质 ,由离子交换法组装了硼酸根插层LDHs ,并用XRD ,FT IR ,TG DTA ,ICP ,11BMASNMR等手段对样品进行了分析和表征 .结果表明 ,通过控制离子交换时的pH ,可使硼酸根取代Mg Al CO3 LDHs前体层间的CO2 -3 ,且可控制离子交换程度及客体的取向 ,从而控制插层结构 .对硼酸根插层LDHs的结构进行研究发现 ,控制pH =4.5 ,层间阴离子主要是一硼酸根和离子平面与LDHs层板平行的三硼酸根 ,出于结构稳定的需要 ,CO2 -3 不能完全被置换 ;控制pH =3 .5 ,层间阴离子是一硼酸根和离子平面与LDHs层板垂直的三硼酸根     

γ-Al2O3表面原位合成Ni-Al-CO3LDHs研究

Ni-Al-CO₃LDHs/γ-Al₂O₃have been prepared using an in-situ synthesis technique. NH₃·H₂O was chosen as activation agent of Al on the γ-Al₂O₃surface as well as precipitant. Ni-Al-CO₃LDHs/γ-Al₂O₃was synthesized by controlling the reaction conditions such as temperature, concentration of Ni²⁺ and initial pH. The crystalline structure, chemical composition and porous structure were characterized by means of XRD, FT-IR, TG-DTA, ²⁷Al MAS-NMR and N₂ adsorption-desorption. The resulting sample of Ni-Al-CO₃LDHs/γ-Al₂O₃possesses higher specific area and narrower pore distribution, in which Ni-Al-CO₃LDHs are located on the surface of γ-Al₂O₃and share the same Al-O bonds with the γ-Al₂O₃lattice. Finally a possible structural model was proposed to account for the porous characters of Ni-Al-CO₃LDHs/γ-Al₂O₃.     

类水滑石及其杂多阴离子柱撑物的合成与表面酸性研究

合成了一些类水滑石和过渡金属取代型杂多酸盐，并由此制备了相应杂多阴离子柱撑水滑石层柱材料。用ＸＲＤ，ＩＲ和元素分析等手段对合成产物进行组成和结构表征，用ＮＨ３－ＴＰＤ，Ｐｙ－ＩＲ研究了合成产物的表面酸性和酸类型，并在异丙醇反应中考察了合成物的酸碱催化行为，结果表明，水滑石和柱撑水滑石均同时存在酸碱中心，且酸碱相对强度与柱阴离子类型密切相关。杂多阴离子进入水滑石层，同时改变了水滑石和杂多酸盐的酸强度     

Investigations of the magnetic properties and structures of the pillared perovskites, La5Re3MO16 (M=Co, Ni)

La₅Re₃CoO₁₆ and La₅Re₃NiO₁₆ were synthesized by solid-state reaction and studied by SQUID magnetometry, heat capacity and powder neutron diffraction measurements. These two compounds belong to a series of isostructural Re-based pillared perovskites [Chi et al. J. Solid State Chem. 170 (2003) 165]. Magnetic susceptibility measurements indicate apparent short-range ferri or ferromagnetic correlations and possible long-range antiferromagnetic order for La₅Re₃CoO₁₆ at 35 K, and at 38 and 14 K for La₅Re₃NiO₁₆. Heat capacity measurements of the Co compound show a lambda anomaly, typical of long-range magnetic order, at 32 K. In contrast, the Ni compound displays a broader, more symmetric feature at 12 K in the heat capacity data, indicative of short-range magnetic order. Low-temperature powder neutron diffraction revealed contrasting magnetic structures. While both show an ordering wave vector, k=(0,0,1/2), in La₅Re₃CoO₁₆, the Co²⁺ and Re⁵⁺ moments are ordered ferrimagnetically within the corner-shared octahedral layers, while the layers themselves are coupled antiferromagnetically along the c-axis, as also found in La₅Re₃MnO₁₆ and La₅Re₃FeO₁₆. In the case of the Ni material, the Re⁵⁺ and Ni²⁺ moments in the perovskite layers couple ferromagnetically and are canted 30° away from the c-axis, angled 45° in the ab-plane. The layers then couple antiferromagnetically at low temperature, a unique magnetic structure for this series. The properties of the La₅Re₃MO₁₆ series, with M=Mn, Fe, Co, Ni and Mg are also reviewed.     

新原料路线共沉淀法组装超分子结构柠檬酸根插层水滑石

以Mg(OH)₂和NaAlO₂为原料，采用新原料路线共沉淀法实现了柠檬酸根插层结构LDHs的超分子组装。用XRD、FT-IR、TG-DTA和元素分析等手段对样品进行分析表征。结果表明，新原料路线共沉淀法较常用的共沉淀法得到的柠檬酸根插层LDHs结晶度高、晶相单一，客体柠檬酸根在LDHs层间的排列高度有序。