Aufbau principle of complex open-framework structures of metal phosphates with different dimensionalities

Open-framework metal phosphates occur as one-dimensional (1D) chains or ladders, two-dimensional (2D) layers, and complex three-dimensional (3D) structures. Zero-dimensional monomers have also been isolated recently. These materials are traditionally prepared by hydrothermal means, in the presence of organic amines, but the reactions of amine phosphates with metal ions provide a facile route for the synthesis, and also throw some light on the mode of formation of these fascinating architectures. Careful studies of the transformations of monophasic zinc phosphates of well-characterized structures show that the 1D structures transform to 2D and 3D structures, while the 2D structures transform to 3D structures. The zero-dimensional monomers transform to 1D, 2D, and 3D structures. There is reason to believe that the 0D monomers, comprising four-membered rings, are the most basic structural units of the open-framework phosphates and that after an optimal precursor state, such as the ladder structure, is formed, further building may occur spontaneously. Evidence for the occurrence of self-assembly in the formation of complex structures is provided by the presence of the structural features of the one-dimensional starting material in the final products. These observations constitute the beginning of our understanding of the building-up principle of such complex structures.     

Building action of various types of inorganic electrolytes

The builder effects of a series of condensed phosphates and other types of electrolytes on the detergency for standard soiled cloth have been measured. The detergency highly depends on the type of electrolytes and, in general, increases with increasing pH of detergent solutions. The building action of phosphates is greater than that of other electrolytes when it is compared at the same pH. The alkalinity, including alkali buffering capacity, of various electrolytes and the sequesteration capacity of phosphates for calcium ion have also been determined. From the results, the building action of inorganic electrolytes in a detersive system has been discussed in connection with the suspension stability of colloidal particles reported in previous papers. The following factors are at least important in the building action of inorganic compounds: (a) the suspension of soil particles in a detergent solution, (b) the sequesteration of heavy metal ions, and (c) the alkalinity including buffering action to keep the solution alkaline. Condensed phosphates, in particular sodium tripolyphophate, have an ability to satisfy these three factors although their alkalinity is not so strong.     

Phosphatfreie Wasch- und Reinigungsmittel

Phosphate-Free Washing and Cleansing Agents Phosphate-free washing and cleansing agents, described in the recent patent literature, can be classified into two groups. The first group is comprised of those, which are neither concerned with phosphates nor their substitutes. A comparatively good cleansing action of these agents is achieved through the use of detergents, which have a larger number of polar groups compared to the conventional detergents. Examples of these detergents are given. The second group concerns phosphate substitutes, especially, low molecular weight inorganic and organic compounds, high molecular weight water soluble organic compounds, and, inorganic as well as organic ion exchangers. Examples of these are also given. Cleansing power of tripolyphosphate-containing washing agents is compared with that of the phosphate-free ones.     

Phosphatfreie Wasch- und Reinigungsmittel

Phosphate-Free Washing and Cleansing Agents Phosphate-free washing and cleansing agents, described in the recent patent literature, can be classified into two groups. The first group is comprised of those, which are neither concerned with phosphates nor their substitutes. A comparatively good cleansing action of these agents is achieved through the use of detergents, which have a larger number of polar groups compared to the conventional detergents. Examples of these detergents are given. The second group concerns phosphate substitutes, especially, low molecular weight inorganic and organic compounds, high molecular weight water soluble organic compounds, and, inorganic as well as organic ion exchangers. Examples of these are also given. Cleansing power of tripolyphosphate-containing washing agents is compared with that of the phosphate-free ones.     

Reticular Chemistry of Multifunctional Metal-Organic Framework Materials

Metal-organic frameworks (MOFs) are crystalline solids constructed by means of reticular chemistry (refers to the connection of molecular building units via strong bonds to make extended structures), which is currently one of the most rapidly expanding platforms for new functional materials. Rational combinations of various building units enable MOFs to show tailorable pore structures. Based on well-established approaches, including the control over pore size and pore chemistry, immobilization of functional sites, post-synthetic modification, and multivariate complex, multifunctional MOFs can be readily synthesized. In this brief review, we summarize and highlight our research progress in MOF chemistry on applications including gas storage, gas separations, optical response, chemical sensing, proton conduction, and molecular recognitions.     

Heterogeneous Enzyme Mimics Based on Zeolites and Layered Hydroxides

Careful combination of a metal compound,a ligand and an inorganic support material leads to supramolecular catalysts that mimic the structural, organizational and functional aspects of enzyme activity.After discussing essential features of metalloenzyme-catalyzed reactions and coordination chemistry in inorganic hosts, we present examples of supramolecular materials selected from our own work that eventually resulted in useful catalysts for organic transformations in the liquid phase.     

纳米磷酸盐及其应用

介绍纳米磷酸盐及其在锂离子电池新型正极材料、生物材料和复合材料领域的应用,纳米磷酸盐抗茵材料及其在陶瓷、建材和消毒领域的应用,纳米磷酸盐发光材料及其在光电材料领域的应用,纳米磷酸盐薄膜及其在高速轴承中的应用。并对我国纳米磷酸盐的发展提出了建议。     

硅酸盐色谱分离中性氨基酸性能研究

将硅酸钠与硫酸铜或硫酸锌按等体积混合 ,制得新型无机离子交换剂硅酸铜、硅酸锌 ,分别用其作为色谱载体对中性氨基酸 (甘氨酸 ,丙氨酸 )进行分离 ,与强酸性阳离子交换树脂 0 0 1× 7的色谱行为作了比较。结果表明 ,合成的硅酸盐具有较好的分离性能。通过不同载体分离中性氨基酸 (甘氨酸 ,丙氨酸 )的流出体积的比较 ,硅酸铜的流出体积大于硅酸锌 ,硅酸锌的流出体积大于 0 0 1× 7。结果显示 ,硅酸铜比硅酸锌更适合于分离中性氨基酸 ,具有最好的分离特性     

Extended structures and physicochemical properties of uranyl-organic compounds

The ability of uranium to undergo nuclear fission has been exploited primarily to manufacture nuclear weapons and to generate nuclear power. Outside of its nuclear physics, uranium also exhibits rich chemistry, and it forms various compounds with other elements. Among the uranium-bearing compounds, those with a uranium oxidation state of +6 are most common and a particular structural unit, uranyl UO(2)(2+) is usually involved in these hexavalent uranium compounds. Apart from forming solids with inorganic ions, the uranyl unit also bonds to organic molecules to generate uranyl-organic coordination materials. If appropriate reaction conditions are employed, uranyl-organic extended structures (1-D chains, 2-D layers, and 3-D frameworks) can be obtained. Research on uranyl-organic compounds with extended structures allows for the exploration of their rich structural chemistry, and such studies also point to potential applications such as in materials that could facilitate nuclear waste disposal. In this Account, we describe the structural features of uranyl-organic compounds and efforts to synthesize uranyl-organic compounds with desired structures. We address strategies to construct 3-D uranyl-organic frameworks through rational selection of organic ligands and the incorporation of heteroatoms. The UO(2)(2+) species with inactive U═O double bonds usually form bipyramidal polyhedral structures with ligands coordinated at the equatorial positions, and these polyhedra act as primary building units (PBUs) for the construction of uranyl-organic compounds. The geometry of the uranyl ions and the steric arrangements and functionalities of organic ligands can be exploited in the the design of uranyl--organic extended structures, We also focus on the investigation of the promising physicochemical properties of uranyl-organic compounds. Uranyl-organic materials with an extended structure may exhibit attractive properties, such as photoluminescence, photocatalysis, photocurrent, and photovoltaic responses. In particular, the intriguing, visible-light photocatalytic activities of uranyl-organic compounds are potentially applicable in decomposition of organic pollutants and in water-splitting with the irradiation of solar light. We ascribe the photochemical properties of uranyl-organic compounds to the electronic transitions within the U═O bonds, which may be affected by the presence of organic ligands.     

The Influences of Excess Sodium on Low‐Temperature NaSICON Synthesis

Controlling the materials chemistry of the solid‐state ion conductor NaSICON is key to realizing its potential utility in emerging sodium‐based battery technologies. We describe here the influence of excess sodium on phase evolution of sol‐gel synthesized NaSICON. Alkoxide‐based sol‐gel processing was used to produce powders of Na₃Zr₂PSi₂O₁₂ NaSICON with 0‐2 atomic % excess sodium. Phase formation and component volatility were studied as a function of temperature. NaSICON synthesis at temperatures between 900‐1100°C with up to 2% excess sodium significantly reduced the presence of zirconia, sodium phosphate, and sodium silicate secondary phases in fired NaSICON powders. Insights into the role of sodium on the phase chemistry of sol‐gel processed NaSICON may inform key improvements in NaSICON development.     

Crystal engineering of NLO materials based on metal--organic coordination networks

Crystal engineering, the ability to predict and control the packing of molecular building units in the solid state, has attracted much attention over the past three decades owing to its potential exploitation for the synthesis of technologically important materials. We present here the development of crystal-engineering strategies toward the synthesis of noncentrosymmetric infinite coordination networks for use as second-order nonlinear optical (NLO) materials. Work performed mainly in our laboratory has demonstrated that noncentrosymmetric solids based on infinite networks can be rationally synthesized by combining unsymmetrical bridging ligands and metal centers with well-defined coordination geometries. Specifically, coordination networks based on 3D diamondoid and 2D grid structures can be successfully engineered with a high degree of probability and predictability to crystallize in noncentrosymmetric space groups. We have also included noncentrosymmetric solids based on 1D chains and related helical structures for comparison.     

蒙脱石制备插层复合材料的研究进展

蒙脱石是一种具有离子交换性的层状硅酸盐粘土矿物,利用其结构特性可以制备插层复合材料。这种通过插层反应得到的复合材料兼有无机主体和客体分子的性质,从而表现出不同于单一组分所具有的催化、吸附以及光、电、磁等性能,在构筑下一代的光学、光电纳米器件,化学或生物传感器,分子识别以及催化等领域存在潜在应用的价值。     

蒙脱石制备插层复合材料的研究进展

蒙脱石是一种具有离子交换性的层状硅酸盐粘土矿物,利用其结构特性可以制备插层复合材料。这种通过插层反应得到的复合材料兼有无机主体和客体分子的性质,从而表现出不同于单一组分所具有的催化、吸附以及光、电、磁等性能,在构筑下一代的光学、光电纳米器件,化学或生物传感器,分子识别以及催化等领域存在潜在应用的价值。     

Metal-organic Frameworks Incorporating Multiple Metal Elements

The obtaining of materials incorporating multiple metal elements is of interest because the combination of various metal cations results in the achievement of new and enhanced properties. Metal-organic frameworks (MOFs) offer a suitable platform to combine multiple metal elements due to their modular nature and highly controllable structure. The incorporation of various metal elements into MOFs might be accomplished by following different synthetic approaches, which in turn determine the way in which the various metal elements are arranged in the framework. In this contribution, we will overview the formation of multi-metal MOFs by the introduction of new metal sites in the organic linkers, or in the inorganic secondary building units through cation exchange process, or one-pot synthesis.     

Rapid generation of molecular complexity in the Lewis or Brønsted acid-mediated reactions of methylenecyclopropanes

Although they are highly strained, methylenecyclopropanes (MCPs) are readily accessible molecules that have served as useful building blocks in organic synthesis. MCPs can undergo a variety of ring-opening reactions because the release of cyclopropyl ring strain (40 kcal/mol) can provide a thermodynamic driving force for reactions and the π-character of the bonds within the cyclopropane can afford the kinetic opportunity to initiate the ring-opening. Since the 1970s, the chemistry of MCPs has been widely explored in the presence of transition metal catalysts, but less attention had been paid to the Lewis or Br?nsted acid mediated chemistry of MCPs. During the past decade, significant developments have also been made in the Lewis or Br?nsted acid mediated reactions of MCPs. This Account describes chemistry developed in our laboratory and by other researchers. Lewis and Br?nsted acids can be used as catalysts or reagents in the reactions of MCPs with a variety of substrates, and substituents on the terminal methylene or on the cyclopropyl ring of MCPs significantly affect the reaction pathways. During the past decade, we and other researchers have found interesting transformations based on this chemistry. These new reactions include the ring expansion of MCPs, cycloaddition reactions of MCPs with aldehydes and imines, cycloaddition reactions of MCPs with nitriles in the presence of strong Br?nsted acid, radical reactions of MCPs with 1,3-dicarbonyl compounds, intramolecular Friedel-Crafts reactions of MCPs with arenes, acylation reactions of MCPs, and the reaction of MCPs with 1,1,3-triarylprop-2-yn-1-ols or their methyl ethers. These Lewis or Br?nsted acid mediated reactions of MCPs can produce a variety of new compounds such as cyclobutanones, indenes, tetrahydrofurans, and tetrahydroquinolines. Finally, we have also carried out computational studies to explain the mechanism of the Br?nsted acid mediated reactions of MCPs with acetonitrile.     

Mesostructured Silica for Optical Functionality, Nanomachines, and Drug Delivery

Silica thin films and nanoparticles prepared using sol–gel chemistry are derivatized with active molecules to generate new functional materials. The mild conditions associated with sol–gel processing allow for the incorporation of a range of dopants including organic or inorganic dyes, biomolecules, surfactants, and molecular machines. Silica nanoparticles embedded with inorganic nanocrystals, and films containing living cells have also been synthesized. Silica templated with surfactants to create mesostructure contains physically and chemically different regions that can be selectively derivatized using defined techniques to create dynamic materials. Using two different techniques, donor–acceptor pairs can be doped into separated regions simultaneously and photo-induced electron transfer between the molecules can be measured. Mesoporous silica materials are also useful supports for molecular machines. Machines including snap-tops and nanoimpellers that are designed to control the release of guest molecules trapped within the pores are described. Mesoporous silica nanoparticles are promising materials for drug delivery and other biomedical applications because they are nontoxic and can be taken up by living cells. Through appropriate design and synthesis, multifunctional mesoporous silica nanoparticles for sophisticated bio-applications are created.     

Design and synthesis of metal-carboxylate frameworks with permanent microporosity

Metal-carboxylate clusters are ideally suited as secondary building units (SBU) for the assembly of extended open frameworks. Examples extracted from the chemistry of the multidentate building block 1,4-benzenedicarboxylate (BDC) show that Zn(BDC) clusters lead to the formation of rigid, stable and truly microporous metal-carboxylate networks. Gas sorption isotherms measured for this class of materials show type (I) gas uptake that is analogous to those observed for zeolites and molecular sieves. This revised version was published online in August 2006 with corrections to the Cover Date.     

Increasing Heavy Metal Tolerance by the Exogenous Application of Organic Acids

Several metals belong to a group of non-biodegradable inorganic constituents that, at low concentrations, play fundamental roles as essential micronutrients for the growth and development of plants. However, in high concentrations they can have toxic and/or mutagenic effects, which can be counteracted by natural chemical compounds called chelators. Chelators have a diversity of chemical structures; many are organic acids, including carboxylic acids and cyclic phenolic acids. The exogenous application of such compounds is a non-genetic approach, which is proving to be a successful strategy to reduce damage caused by heavy metal toxicity. In this review, we will present the latest literature on the exogenous addition of both carboxylic acids, including the Kreb’s Cycle intermediates citric and malic acid, as well as oxalic acid, lipoic acid, and phenolic acids (gallic and caffeic acid). The use of two non-traditional organic acids, the phytohormones jasmonic and salicylic acids, is also discussed. We place particular emphasis on physiological and molecular responses, and their impact in increasing heavy metal tolerance, especially in crop species.     

Verminderung des Cadmium-Gehaltes von Rohphosphaten und Mineraldüngern

Reducing the cadmium content of crude phosphates and mineral fertilizers . Crude sedimentary phosphates generally contain cadmium together with traces of other heavy metals. These Cd traces generally end up in fertilizers produced from the crude phosphates. Processes have therefore been developed to separate the Cd from the crude phosphate or from the crude phosphoric acids arising therefrom as intermediates. In this way, the Cd content of the crude phosphate can be reduced to less the 10% of its original value, and to 50% thereof by extractive treatment with acidic calcium nitrate solution. Older calcination processes for crude phosphate have been improved to give residual Cd contents of 10 to 50% at temperatures of 800 to 1000°C. Cadmium can be removed almost quantitatively from crude phosphate by means of dialkyl dithiophosphoric acid esters by extraction, binding to adsorbents, or ion flotation. Cadmium can be extracted from crude acids in high yield by long-chained amines. After partial neutralization of the crude acids, precipitation as cadmium sulphide is also possible.     

Sol-gel derived composites from poly(silicic acid) and 2-hydroxyethylmethacrylate: thermal, physical and morphological properties

Hybrid materials based on poly(silicic acid) and 2-hydroxyethylmethacrylate were prepared and characterized. The glass transition temperatures of a homologous series of samples were measured by dynamic mechanical thermal analysis and the location of the transition and shape of the spectra shown to be dependent on the morphology of the inorganic phase which was able to be manipulated by variation of synthetic conditions. A number of other techniques including small angle X-ray scattering, electron microscopy, density and free volume measurements were used to help elucidate inorganic-organic miscibility and structure.It was shown that incorporation of organic polymeric phase to crosslinked inorganic silicate led to the formation of the system that is similar to interpenetrating polymeric networks. A high level of miscibility as determined by small angle X-ray scattering and transmission electron microscopy was demonstrated. This was also demonstrated in DMTA traces as seen by the mobility of the organic phase being determined by the degree of crosslinking of the inorganic component. Nonetheless, there appear to be a slight influence of silicate architecture on molecular packing and miscibility. Highly branched, higher molecular weight silicate materials appear to be slightly less miscible.