Time‐Resolved In Situ MAS NMR Monitoring of the Nucleation and Growth of Zeolite BEA Catalysts under Hydrothermal Conditions

Time‐resolved ¹³C, ²³Na, ²⁷Al, and ²⁹Si MAS NMR has been applied in situ for monitoring the hydrothermal synthesis of zeolite BEA. Isotopic labelling with ²⁹Si and ¹³C isotopes has been used to follow the fate of siliceous species and structure directing agent ((¹³CH₃−CH₂)₄NOH). Two mechanistic pathways, namely solution‐mediated and solid–solid hydrogel rearrangement have been distinguished for two synthesis procedures studied. The mechanisms of structure‐directing behavior of TEA⁺ cations in two reaction pathways have been elucidated. The results show that multinuclear MAS NMR can serve as a superior tool for monitoring hydrothermal synthesis of various solids including zeolites, zeotypes, mesoporous materials, metal–organic frameworks and so on and for the design of novel outstanding materials for different applications.     

无机固体功能材料的水热合成化学

综述了无机固体功能材料的水热合成化学进展。重点强调强关联系固体、无机-有机杂化材料、缺陷与混合价态固体、三重价态与原子尺度p-n结以及水热生物化学。     

Phosphomolybdate clusters as molecular building blocks in the design of one-, two- and three-dimensional organic-inorganic hybrid materials

An attractive approach to the design of inorganic solids exploits the tethering of inorganic clusters through organic spacers to produce hybrid materials with composite properties. We have recently described a modified strategy in which polyoxometalate clusters are linked through organic subunits to give an anionic hybrid substructure which may be further modified through the introduction of secondary metal-ligand complex (SMLC) cations, serving as a third component building block. In this application, the molybdophosphonate cluster {Mo₅O₁₅(O₃PR)₂}⁴⁻ serves as a secondary building unit (SBU) with alkyl (CH₂)_n or aromatic -(C₆H₄)_n- tethers providing one-dimensional structural expansion. A binucleating ligand such as tetrapyridylpyrazine (tpyprz) is used to bridge secondary metal sites into a binuclear {Cu₂(tpyprz)}⁴⁺ SBU which may link phosphomolybdate clusters into two- or three-dimensional structures. The influence of a variety of structural determinants is discussed, including the tether length of the diphosphonate ligand, the coordination preferences of the secondary metal, expansion of the ligand component of the SMLC, and substitution of As for P in the oxide SBU.     

The First Vanadium Oxide Nanotubes Containing an Aromatic Amine as Template

A new vanadate has been prepared in high yield by reacting vanadium(V) triisopropoxide and 3‐phenylpropylamine in solution, followed by hydrolysis and hydrothermal treatment of the intermediate product. For the first time, an aromatic amine has successfully been applied as structure‐directing template for the synthesis of vanadium oxide nanotubes. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images demonstrate the tubular morphology of the phenylpropylamine vanadium oxide nanotubes obtained. The size and structure are similar to that of vanadium oxide nanotubes formed with aliphatic amines. The tube walls comprise layers of vanadium oxide with the organic template intercalated in between. The interlayer distance is ca. 2.1 nm, and the structure of the VO_x layers can be described by a square lattice with a≈0.61 nm. Furthermore, the TEM investigation has revealed the presence of many defects in the wall structure.     

Reversible Topotactic Redox Reactions of Solids by Electron/Ion Transfer

Solids having suitable structural and electronic properties are able to form intercalation compounds by reversible redox reactions at room temperature via topotactic electron/ion transfer processes. The host lattices range from inorganic solids with different structural dimensionality to organic molecular solids. Similarly, depending on the host lattice type, the guest species may vary from protons and metal ions to large inorganic and organic molecular ions. The possibilities of a systematic “tailoring” of new stable or metastable compounds, the controlled modification of physical properties of solids, and the technical application of electronic/ionic conductors, provide a wide and attractive field for academic and applied research in an interdisciplinary area that involves solid state chemistry and physics, molecular chemistry, electrochemistry, and interface science.     

C<Subscript>18</Subscript>-Free Organic–Inorganic Hybrid Silica Particles Derived from Sole Silsesquioxane for Reversed-Phase HPLC

Ethyl-bridged organic–inorganic hybrid silica particles were prepared via a sol–gel and hydrothermal synthesis approach using 1,2-bis(triethoxysilyl)ethane (BTESE) as the sole precursor, and triblock copolymer poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (P123) and dodecyltrimethylammonium bromide (DTAB) as combined templates. The morphology, pore structure, chemical composition and liquid chromatographic performance of the obtained materials were investigated in detail. The particles exhibit a high surface area of 1136.40 m²/g, together with a pore volume of 0.39 cm³/g and an average pore size of 2.30 nm. Used as stationary phase for high-performance liquid chromatography (HPLC), the particles without extra bonding either C₁₈ or C₈ can successfully separate a mixture of uracil, phenol, pyridine, methylbenzene, ethylbenzene and tert-butylbenzene. The obtained materials also show practical application in the separation of phthalate acid esters (PAEs), which are harmful to environment and human health. Although the columns packed with ethyl-bridged organic–inorganic hybrid silica show lower column efficiency and peak symmetry compared to commercial column, they have considerably higher chemical stability in alkaline mobile phase. The HSS column also possesses high mechanical stability which is similar to that of the commercial column.     

Solid polymer electrolytes. VI. Microstructure of organic–inorganic hybrid networks composed of 3‐glycidoxypropyltrimethoxysilane and LiClO4 and affected by different synthetic routes

Hybrid organic–inorganic materials derived from 3‐glycidoxypropyltrimethoxylsilane were prepared via two different synthetic routes: (1) the HCl‐catalyzed sol–gel approach of silane followed by the lithium perchlorate (LiClO₄)/HCl‐catalyzed opening of epoxide and (2) the simultaneous gelation of tin/LiClO₄‐catalyzed silane/epoxide groups. LiClO₄ catalyzed the epoxide polymerization, and its effects on the structures of these hybrid materials were studied by NMR. The structure of the inorganic side was probed by solid‐state ²⁹Si NMR spectroscopy, and the characterizations of the organic side and the chemical processes involved in the different synthetic routes were performed with solid‐state cross‐polarity/magic‐angle‐spinning ¹³C NMR. The different synthetic routes significantly affected the polymerization behaviors of the organic and inorganic sides in the presence of LiClO₄. A larger amount of LiClO₄ promoted the opening of epoxide and led to the formation of longer poly(ethylene oxide) chains via the HCl‐catalyzed sol–gel approach, whereas in the case of the tin‐catalyzed approach, the faster polymerization of the inorganic side hindered the growth of the organic network. The addition of LiClO₄ was proven to be without crystalline salt present in the hybrid networks by wide‐angle X‐ray powder diffraction. Also, the interactions between the ions and hybrid host, examined with Fourier transform infrared and ⁷Li proton‐decoupled magic‐angle‐spinning NMR, further demonstrated that extensive ion aggregation existed in these hybrid materials. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 151–161, 2004     

Fullerenes in Sol-Gel Materials

The family of fullerene molecules is composed of a large variety of compounds that have been synthesized following the discovery of C₆₀ in 1985. The chemistry of fullerenes, developed in these last years, has allowed designing the properties of this family of molecules for specific applications in materials science. One of the main tasks to build up solid state devices based on fullerenes is the synthesis of materials doped with a highly dispersed and homogeneous distribution of fullerenes. Many of the peculiar photophysical properties, such as the reverse saturable absorption used to obtain a solid state optical limiter, are in fact lost in the aggregates of fullerenes. Sol-gel processing allows preparing inorganic oxides and hybrid organic-inorganic materials at low temperatures and presents an interesting alternative to organic polymers to entrap molecules of the fullerene family in a solid matrix. Porous inorganic solids and aerogels are also important classes of materials that can be synthesized via sol-gel and can act as hosts of fullerenes. In the present article we have reviewed the main achievements of sol-gel processing of fullerene based nanocomposite materials.     

Synthesis of polyoxovanadates via “chimie douce”

A large variety of new polyoxovanadates have been synthesized during the past few years by sol–gel chemistry or hydrothermal methods. These wet chemistry methods offer many advantages compared to the usual solid state syntheses. New open structures have been obtained from aqueous precursors. They result from the self-assembling of ionic species in the solution.Vanadium oxide gels and sols, V₂O₅·nH₂O, are formed around the point of zero charge (pH≈2). They have a ribbon-like structure and exhibit a liquid crystal behavior. These mesophases are similar to those currently observed with nematic polymers. Xerogel layers deposited from V₂O₅·nH₂O gels exhibit some preferred orientation and behave as versatile host structures for intercalation giving new hybrid organic–inorganic nanocomposites.Layered structures are formed around pH≈7 in the presence of large organic cations. They are built of mixed valence polyoxovanadate planes made of [VO₅] pyramids and [VO₄] tetrahedra. Organic cations lie between the oxide layers where they interact with the negative oxygen of the VO double bonds.Anions can behave as templating agents. Hollow cluster shells are formed around anions that remain encapsulated within the negatively charged polyvanadate cage. Large cations only behave as counter ions for the formation of a neutral crystalline network.It appears that the molecular structure of V^V precursors depends mainly on pH, but the way they self-assemble may be governed by other ionic species in the solution.     

[M3V18O42(H2O)12(XO4)]⋅24 H2O (M=Fe,Co; X=V,S): Metal Oxide Based Framework Materials Composed of Polyoxovanadate Clusters

New framework materials composed of well-defined vanadium oxide clusters were prepared by low-temperature reactions and characterized by X-ray crystal structure analysis. The structures of these solids contain {V₁₈O₄₂} cages linked into two interpenetrating three-dimensional networks by bridging {M(H₂O)₄} groups (M=Fe^II, Co^II; see picture).     

Perovskite Oxides Prepared by Hydrothermal and Solvothermal Synthesis: A Review of Crystallisation,Chemistry, and Compositions

Perovskite oxides with general composition ABO₃ are a large group of inorganic materials that can contain a variety of cations from all parts of the Periodic Table and that have diverse properties of application in fields ranging from electronics, energy storage to photocatalysis. Solvothermal synthesis routes to these materials have become increasingly investigated in the past decade as a means of direct crystallisation of the solids from solution. These methods have significant advantages leading to adjustment of crystal form from the nanoscale to the micron-scale, the isolation of compositions not possible using conventional solid-state synthesis and in addition may lead to scalable processes for producing materials at moderate temperatures. These aspects are reviewed, with examples taken from the past decade's literature on the solvothermal synthesis of perovskites with a systematic survey of B-site cations, from transition metals in Groups 4–8 and main group elements in Groups 13, 14 and 15, to solid solutions and heterostructures. As well as hydrothermal reactions, the use of various solvents and solution additives are discussed and some trends identified, along with prospects for developing control and predictability in the crystallisation of complex oxide materials.     

有机物单层分散在相关材料制备中的应用

与无机氧化物和盐类在载体表面自发单层分散相类似, 许多有机物也可以在载体表面自发单层分散.有机物在载体表面单层分散行为和分散后的存在状态与有机物分子形状和结构特点及载体表面性质和孔结构有关. 利用有机物在载体表面的单层分散, 可以设计制备具有优异性能的材料. 本文简要综述了近年来这方面研究工作取得的相关进展, 主要介绍了有机物单层分散在碳/氧化物复合物、氧化物和薄壁中孔碳材料的制备和织构调控方面的一些应用实例. 单层分散的有机物热分解后可在载体表面形成均匀的薄碳层, 以无机多孔氧化物为载体可制备出包覆均匀碳薄层的碳/氧化物复合物, 这种碳/氧化物复合物在染料吸附、催化剂载体和光催化方面显现出好的性能. 以溶胶-凝胶法制备氧化物时, 分散的有机物可以隔离溶胶颗粒, 从而制备出高比表面积的氧化物并可对孔容进行调控, 以此方法制备的γ-氧化铝比表面积可达506 m²·g^-1. 在惰性气氛中加热上述碳/氧化物复合物, 碳层可抑制氧化物的相变; 而在氧气中, 碳层燃烧发热会促进相变, 由此可快速制备超细α-氧化铝. 包覆均匀碳薄层的氧化物载体对碳起支撑作用, 在将氧化物溶解去除后, 可便捷制得高比表面积、大孔容、高中孔率的薄壁中孔碳材料, 碳材料的形貌、孔径分布等可通过选用不同织构的氧化物载体进行调控.     

Ceramics and Nanostructures from Molecular Precursors

The elaboration of solids from the molecular scale by a kinetically controlled methodology is one of the main challenges of molecular chemistry. In the long term, this should permit the design of solids with desired properties. Here, some examples are given which show a few methods that have been used for the preparation of solids from molecular precursors. The one-pot synthesis of rheologically controlled SiC is described. Access to a new kind of ceramic is obtained by the same methodology using molecular precursors. Mixed ceramics with interpenetrating networks are not accessible by the chemical thermodynamic route. The chemistry of hybrid materials obtained from molecular precursors through inorganic polymerization is presented. This class of materials offers wide perspectives because of 1) the large possibilities opened by the organic unit, 2) the kinetic control, which permits any kind of texture for the solid, and 3) the aptitude of these solids to become nanostructured.     

Organic–Inorganic Hybrid Materials: From “Simple” Coordination Polymers to Organodiamine-Templated Molybdenum Oxides

A blueprint for the design of oxide materials is provided by nature. By borrowing from nature's ability to influence inorganic microstructures in biomineralization processes and in the hydrothermal synthesis of complex minerals, a new class of materials in which organic components exert a role in controlling inorganic microstructure is evolving. By employing members of the ever-expanding class of polymeric coordination complex cations, novel molybdenum oxide substructures, such as the one shown, may be prepared.     

Extending the Family of V4+ S=${{ 1/2 }}$ Kagome Antiferromagnets

The ionothermal synthesis, structure, and magnetic susceptibility of a novel inorganic–organic hybrid material, imidazolium vanadium(III,IV) oxyfluoride [C₃H₅N₂][V₉O₆F₂₄(H₂O)₂] (ImVOF) are presented. The structure consists of inorganic vanadium oxyfluoride slabs with kagome layers of V⁴⁺ S=${{ 1/2 }}$ ions separated by a mixed valence layer. These inorganic slabs are intercalated with imidazolium cations. Quinuclidinium (Q) and pyrazinium (Pyz) cations can also be incorporated into the hybrid structure type to give QVOF and PyzVOF analogues, respectively. The highly frustrated topology of the inorganic slabs, along with the quantum nature of the magnetism associated with V⁴⁺, means that these materials are excellent candidates to host exotic magnetic ground states, such as the highly sought quantum spin liquid. Magnetic susceptibility measurements of all samples suggest an absence of conventional long‐range magnetic order down to 2 K despite considerable antiferromagnetic exchange.     

Nanoporous materials: a good opportunity for nanosciences

This paper emphasizes the wide possibilities open to organometallic chemistry by the bottom-up approach for nanosciences. In this new field of research, organometallic chemistry and coordination chemistry are in position to play a very important role in the development of nanomaterials. At first, organometallic and coordination chemistries will be the mothers of plenty of nanotools, which are the elemental bricks of nanosciences. The nanomaterials are obtained from them either by inclusion in a matrix (Nanocomposites) or by grafting methods (grafted nanomaterials). However, the most exciting field of investigation are the nanostructured hybrid materials which permit to open new fields of investigation such as self-organization of organic moieties or the coordination chemistry in the solid. Some examples are given. Moreover, the organometallic chemistry performed on both the framework and the pores of the nanoporous solids obtained by sol-gel chemistry in the presence of structure directing agents is opening the way to smart materials. These materials will have the ability to couple interactively two different properties.     

V2O5 xerogel-poly(ethylene oxide) hybrid material: Synthesis, characterization, and electrochemical properties

In this work, we report the synthesis, characterization, and electrochemical properties of vanadium pentoxide xerogel-poly(ethylene oxide) (PEO) hybrid materials obtained by varying the average molecular weight of the organic component as well as the components’ ratios. The materials were characterized by X-ray diffraction, ultraviolet/visible and infrared spectroscopies, thermogravimetric analysis, scanning electron microscopy, electron paramagnetic resonance, and cyclic voltammetry. Despite the presence of broad and low intensity peaks, the X-ray diffractograms indicate that the lamellar structure of the vanadium pentoxide xerogel is preserved, with increase in the interplanar spacing, giving evidence of a low-crystalline structure. We found that the electrochemical behaviour of the hybrid materials is quite similar to that found for the V₂O₅ xerogel alone, and we verified that PEO leads to stabilization and reproducibility of the Li⁺ electrochemical insertion/de-insertion into the V₂O₅ xerogel structure, which makes these materials potential components of lithium ion batteries.     

Vanadium oxide aerogels: Nanostructured materials for enhanced energy storage

The synthesis, chemistry, local structure and electrochemical properties of vanadium oxide xerogels and aerogels have much in common. The one difference in their respective synthesis routes, the means by which solvent is removed, has a significant influence on the resulting morphology. The high surface area, nanodimensional solid phase, short diffusion paths and interconnected mesoporosity of the aerogels exert a profound effect on their electrochemical properties. Our studies with V₂O₅ aerogels show that these materials offer the promise of achieving both high energy density and high power density because of a pseudocapacitive charge storage mechanism which develops.     

The Cross‐Sectional Structure of Vanadium Oxide Nanotubes Studied by Transmission Electron Microscopy and Electron Spectroscopic Imaging

Vanadium oxide nanotubes (VO_x‐NTs) are easily accessible in pure form from vanadium(V) alkoxides and amines by a sol‐gel reaction and a subsequent hydrothermal treatment. The wall structure of VO_x‐NTs containing hexadecylamine or dodecylamine as the structure‐directing template has been characterised by transmission electron microscopy (TEM). A standard method for preparing TEM specimens was modified in order to investigate the cross‐sectional structure of the tubes. The elemental distribution in the layered structure inside the tube walls has been visualised by electron spectroscopic imaging: vanadium oxide builds up the layers that appear with dark contrast in the TEM images while carbon, i. e., the organic template, is present in between. The bent VO_x layers inside the tube walls are preferentially scrolls rather than concentric cylinders. Moreover, some tubes are formed by a combination of both types. The layer structure inside the tube walls is frequently disordered, and several types of defects appear.     

Solid Polymer Electrolyte Based on Pluronic P123 Triblock Copolymer‐Siloxane Organic‐Inorganic Hybrid

A novel organic‐inorganic hybrid electrolyte based on poly(ethylene oxide)‐poly(propylene oxide)‐poly(ethylene oxide) triblock copolymer (Pluronic P123) complexed with LiClO₄ via the co‐condensation of an epoxy trialkoxysilane and tetraethylorthosilicate was prepared. Characterization was made by a variety of techniques including powder X‐ray diffraction, AC impedance, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and multinuclear solid state NMR measurements. The hybrid with [O]/[Li] = 16 exhibited a mesophase with a certain degree of ordering, which arose by the self‐assembly of P123 with the silica network. The P123 triblock copolymer acts as a structure‐directing surfactant to organize with silica networks and as a polymer matrix to dissolve alkali lithium salts as well. The DSC results indicated the formation of transient crosslinking between Li⁺ ions and the ether oxygens of the EO and PO segments, resulting in an increase the T_g with increasing salt concentrations. Variable temperature ⁷Li‐{¹H} MAS NMR spectra revealed the presence of two different local environments for lithium cations, probably due to the lithium cations in the polymer‐rich domain and in the silica‐rich domain, respectively. A combination of XRD and conductivity results suggests that the drastically enhanced conductivity for the ordered hybrid electrolyte is closely related to the formation of mesophase, which may provide unique Li⁺ conducting pathways.