共聚法和嫁接法制备二茂铁杂化介孔材料及其催化性能

 以桥联硅氧烷 1,1'-双[(2-三乙氧基硅基) 乙基]二茂铁 (BTEF) 和正硅酸乙酯为前驱体, 以十六烷基三甲基溴化铵为结构导向剂, 采用共聚法制备了二茂铁功能化的周期介孔有机硅烷材料 (PMO-Fc). 同时以 BTEF 为修饰剂, 以甲苯为分散剂, 采用嫁接法制备了 Fc-MCM-41 杂化介孔材料. 采用 N2 物理吸附、X 射线衍射、透射电镜和红外光谱等手段对材料进行了表征, 评价了其催化苯羟化反应活性. 结果表明, PMO-Fc 具有有序的二维六方形孔道结构, 较大的比表面积和孔体积, 在苯羟化反应中表现出比 Fc-MCM-41 更高的催化活性, 苯酚的选择性和收率分别为 65.3% 和 20.2%.     

Preparation of silica microspheres with a broad pore size distribution and their use as the support for a coated cellulose derivative chiral stationary phase

A templating strategy using crosslinked and functionalized polymeric beads to synthesize silica microspheres with a broad pore size distribution has been developed. The polymer/silica hybrid microspheres were prepared by utilizing the combination of a templating weak cation exchange resin, a structure‐directing agent N‐trimethoxysilylpropyl‐N,N,N‐trimethylammonium chloride, and a silica precursor tetraethyl orthosilicate. The silica microspheres were then obtained after calcinating the hybrid microspheres. The as‐prepared materials were characterized by scanning electron microscopy, mercury intrusion porosimeter, and thermal gravimetric analysis. The results showed that the starting templating beads were about 5 μm in diameter and the formed silica microspheres were less than 3 μm with a pore size range of 10–150 nm, some pores were even extended to beyond 250 nm. It was demonstrated that cellulose tris(3,5‐dimethylphenylcarbamate) was readily coated onto the surface of the as‐synthesized silica microspheres without any additional surface pretreatment. The coated silica microspheres were uniformly dispersed even with high loading of the chiral stationary phase, which exhibited high resolution chiral separations in high‐performance liquid chromatography.     

Preparation of uniform silica/polypyrrole core/shell microspheres and polypyrrole hollow microspheres by the template of modified silica particles using different modified agents

Silica/polypyrrole (PPY) core/shell microspheres and PPY hollow microspheres were prepared by the template of silica particles whose surface character was modified with different modified agents. The morphology and structure of the particles were characterized by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Elemental analysis and X-ray photoelectron spectroscopy (XPS) were carried out to characterize the structure of PPY hollow microspheres. We investigated the effect of different modified agents on the surface character of silica particles and the effect of surface character of silica particles on the morphology of PPY hollow microspheres. The effect of reaction conditions on the size of core/shell particles and hollow particles was also studied.     

硅酸钠与有机硅氧烷前驱体自组装杂化硅基中孔材料

采用有机硅氧烷(RTES)与硅酸钠(Na2SiO3)共水解缩聚合成有机官能化的MSU型硅基中孔材料.考察了合成体系pH值对材料织构性能的影响以及不同有机硅氧烷与硅酸钠在中性条件下的自组装行为.发现在中性条件下，加入NaF可以有效避免带有较小有机基团的有机硅氧烷进入材料孔壁的可能性，而且合成体系的pH值对材料的孔径有一定的调控作用.     

Preparation of Fluorescent Thiol Group‐Functionalized Silica Microspheres for the Detection and Removal of Silver Ions in Aqueous Solutions

We demonstrate that silica microspheres can act as a sensitive fluorescent sensor and adsorbent of Ag⁺ in aqueous media. These thiol‐functionalized silica microspheres are doped with quantum dots (QDs) using organosilane chemistry in a one‐step preparation. Ligand exchange takes place between the thiolated organosilane and acid‐capped QDs, making the doping easy. Ag⁺ adsorption by the silica microspheres causes the decrease of fluorescence intensity of the QDs. The detection limit for Ag⁺ is found to be 10 μmol/L. The abundance of thiol groups on the surface of the microspheres could effectively remove Ag⁺ through strong interaction. When microspheres with a diameter of 1.1 μm are used as the adsorbents, the adsorption capacity for Ag⁺ reached 102 mg/g. This excellent adsorption ability is due to the abundance of thiol groups that act as the active sites, facilitating the adsorption of the massive metal ions on the surface of the microspheres. Furthermore, the adsorption isotherm data follows the Freundlich model. The structure and content of the silica microspheres were investigated by scanning and high‐resolution transmission electron microscopy, energy dispersive X‐ray spectroscopy, and Raman analysis, and the fluorescence properties were characterized by fluorescence microscopy.     

Functionalized organosilica microspheres via a novel emulsion-based route

Thiol-functionalized organosilica microspheres were synthesized via a two-step process: (1) acid-catalyzed hydrolysis and condensation of 3-mercaptopropyltrimethoxysilane (MPTMS), followed by (2) base-catalyzed condensation, which led to the rapid formation of emulsion droplets with a narrow size distribution. These droplets continued to condense to form solid microspheres. Solution (29)Si NMR and optical microscopy were applied to study the mechanism of this novel synthetic route. Solid-state (29)Si NMR, SEM, zeta potential titration, and Coulter counter measurements were used to study the bulk and surface properties and to determine the particle size distributions of the final microspheres. Compared to conventional St?ber silica particles, these microspheres were shown to have a lower degree of cross-linking (average degree of condensation, r = 1.25), a larger average size (up to 6 microm), and a higher isoelectric point (pH = 4.4). Confocal microscopy of dye-labeled microspheres showed an even distribution of dye molecules throughout the interior, characteristic of a readily accessible and permeable organosilica network. These findings have implications for the production of functionalized solid supports for use in catalysis and biological applications, such as optically encoded carriers for combinatorial synthesis.     

Structural Changes of Hierarchically Nanoporous Organosilica/Silica Hybrid Materials by Pseudomorphic Transformation

Herein, it is reported how pseudomorphic transformation of divinylbenzene (DVB)-bridged organosilica@controlled pore glasses (CPG) offers the possibility to generate hierarchically porous organosilica/silica hybrid materials. CPG is utilized to provide granular shape/size and macroporosity and the macropores of the CPG is impregnated with organosilica phase, forming hybrid system. By subsequent pseudomorphic transformation, an ordered mesopore phase is generated while maintaining the granular shape and macroporosity of the CPG. Surface areas and mesopore sizes in the hierarchical structure are tunable by the choice of the surfactant and transformation time. Two-dimensional magic angle spinning (MAS) NMR spectroscopy demonstrated that micellar-templating affects both organosilica and silica phases and pseudomorphic transformation induces phase transition. A double-layer structure of separate organosilica and silica layers is established for the impregnated material, while a single monophase consisting of randomly distributed T and Q silicon species at the molecular level is identified for the pseudomorphic transformed materials.     

Dendrimers and Hyperbranched Polyesters as Structure‐Directing Agents in the Formation of Nanoporous Silica

Anionic dendritic macromolecules (hyperbranched polyesters and polyamidoamine (PAMAM) dendrimers) and amine‐functionalized PAMAM dendrimers have been used as structure‐directing agents in the synthesis of nanoporous silica structures. When utilizing carboxylates as structure‐directing agents the incorporation of the negatively charged species into a SiO₂ framework was achieved via a sol‐gel synthesis route using a quaternized aminosilane as co‐structure‐directing agent to yield silica materials of various morphologies and high surface areas. Amine dendrimers as porogens gave materials with high surface areas, revealing increasing pore sizes corresponding to the increasing size of the porogen. The resulting materials have been characterized by X‐ray diffraction (XRD), N₂ adsorption/desorption (BET), scanning electron microscopy (SEM), infrared spectroscopy (IR), and thermogravimetric analysis (TGA).     

Facile synthesis of nanocrystal encoded fluorescent silica microspheres

Monodisperse CdTe composite microspheres with a spherical shape were prepared using organosilane chemicals in aqueous solution. CdTe nanocrystals (NCs) were loaded into the matrix of silica microspheres during the formation of composite microspheres. Detailed characterization of the CdTe composite microspheres by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and spectrofluorimeter was performed to elucidate the morphology and fluorescence of the composite microspheres. In contrast to CdTe NCs in aqueous solution, CdTe NCs in the composite microspheres revealed high stability and fluorescence due to the confined effects of silica matrix. In addition, multicolored CdTe QDs were encoded into the microspheres at precise ratios.     

Organic-inorganic hybrid mesoporous silicas: functionalization, pore size, and morphology control

Topological design of mesoporous silica materials, pore architecture, pore size, and morphology are currently major issues in areas such as catalytic conversion of bulky molecules, adsorption, host-guest chemistry, etc. In this sense, we discuss the pore size-controlled mesostructure, framework functionalization, and morphology control of organic-inorganic hybrid mesoporous silicas by which we can improve the applicability of mesoporous materials. First, we explain that the sizes of hexagonal- and cubic-type pores in organic-inorganic hybrid mesoporous silicas are well controlled from 24.3 to 98.0 A by the direct micelle-control method using an organosilica precursor and surfactants with different alkyl chain lengths or triblock copolymers as templates and swelling agents incorporated in the formed micelles. Second, we describe that organic-inorganic hybrid mesoporous materials with various functional groups form various external morphologies such as rod, cauliflower, film, rope, spheroid, monolith, and fiber shapes. Third, we discuss that transition metals (Ti and Ru) and rare-earth ions (Eu(3+) and Tb(3+)) are used to modify organic-inorganic hybrid mesoporous silica materials. Such hybrid mesoporous silica materials are expected to be applied as excellent catalysts for organic reactions, photocatalysis, optical devices, etc.     

MCM-48-like large mesoporous silicas with tailored pore structure: facile synthesis domain in a ternary triblock copolymer-butanol-water system

Assembly of mesostructured silica using Pluronic P123 triblock copolymer (EO(20)-PO(70)-EO(20)) and n-butanol mixture is a facile synthesis route to the MCM-48-like ordered large mesoporous silicas with the cubic Iad mesostructure. The cubic phase domain is remarkably extended by controlling the amounts of butanol and silica source correspondingly. The extended phase domain allows synthesis of the mesoporous silicas with various structural characteristics. Characterization by powder X-ray diffraction, nitrogen physisorption, scanning electron microscopy, and transmission electron microscopy reveals that the cubic Iad materials possess high specific surface areas, high pore volumes, and readily tunable pore diameters in narrow distribution of sizes ranging from 4 to 12 nm. Moreover, generation of complementary pores between the two chiral channels in the gyroid Iad structure can be controlled systematically depending on synthesis conditions. Carbon replicas, using sucrose as the carbon precursor, are obtained with either the same Iad structure or I4(1)/a (or lower symmetry), depending on the controlled synthesis conditions for silica. Thus, the present discovery of the extended phase domain leads to facile synthesis of the cubic Iad silica with precise structure control, offering vast prospects for future applications of large-pore silica materials with three-dimensional pore interconnectivity.     

有机胺修饰具有较大孔径介孔材料的二氧化碳吸附性能

以非离子表面活性剂P123为模板剂,正硅酸甲酯为硅源,通过加入不同的扩孔剂制得具有较大孔径的SBA-15类介孔材料,并采用粉末X射线衍射(XRD)、低温氮气吸附-脱附、扫描电镜(SEM)、傅里叶变换红外(FTIR)光谱等手段对所得样品进行了表征.加入扩孔剂可以明显增大介孔材料的孔容和孔径,而异辛烷为扩孔剂的扩孔效果明显优于四氯化碳.经四乙烯五胺(TEPA)镀饰后,这些样品均表现出良好的CO2吸附性能.其中对于除去模板剂后再镀胺的样品,其CO2吸附能力与介孔材料孔道结构关系不大,而对于未除模板剂的原粉镀胺样品,CO2吸附能力则随孔道的变大而增强.此外,通过吸附等温线和CO2-程序升温脱附(TPD)手段比较了温度和压力对CO2吸附的影响,发现在较高温度下吸附时CO2的吸附能力随压力的变化存在显著差别,因而在这类TEPA修饰的介孔材料上可通过变压吸附的途径来实现对环境气流中CO2的吸附和分离.     

Adsorption characteristics of organosilica based mesoporous materials

Hybrid organosilica mesoporous materials with pores of ordered three-dimensional hexagonal structure were prepared by the hydrolysis and co-condensation of 1,2-bis(triethoxysilyl)ethane with various concentrations of a surfactant as structure directing agents. The materials had high pore volume of 1-1.5 mL/g and high surface area from 1057 to 1445 m(2)/g. Adsorption measurement and adsorption calorimetry revealed that the prepared materials exhibited high hydrophobicity and high affinity toward nonpolar organic vapor such as n-hexane. The dynamic adsorption properties of the materials for n-hexane in the presence of water vapor showed that these hybrid organosilica materials preferentially adsorbed n-hexane vapor and were stable in the presence of water compared to the siliceous MCM48.     

A controlled release of ibuprofen by systematically tailoring the morphology of mesoporous silica materials

A series of mesoporous silica materials with similar pore sizes, different morphologies and variable pore geometries were prepared systematically. In order to control drug release, ibuprofen was employed as a model drug and the influence of morphology and pore geometry of mesoporous silica on drug release profiles was extensively studied. The mesoporous silica and drug-loaded samples were characterized by X-ray diffraction, Fourier transform IR spectroscopy, N₂ adsorption and desorption, scanning electron microscopy, and transmission electron microscopy. It was found that the drug-loading amount was directly correlated to the Brunauer-Emmett-Teller surface area, pore geometry, and pore volume; while the drug release profiles could be controlled by tailoring the morphologies of mesoporous silica carriers.     

In Situ and Post Reaction Cobalt-Incorporation into Periodic Mesoporous Ethanesilica Materials

Cobalt incorporated periodic mesoporous organosilica materials were synthesized in situ by condensation of 1,2-bistrimethoxysilylethane (BTME) in the presence of cetyltrimethylammonium bromide (CTAB) and cobalt nitrate and by incipient wetness addition of Co to BTME mesoporous silica. BET and pore measurements as well as DTA and TGA analysis of the materials revealed that the mesoporous structure is retained under the synthetic conditions used, after solvent extraction and importantly to temperatures of ca. 400°C under N₂. Raman spectroscopy also revealed the presence of the ethane moiety in the Co materials and that the surfactant was removed by solvent extraction. BET and pore measurement studies revealed that the surface area and pore volume of the materials decreased with increasing cobalt loading. The studies indicate that the new Co materials have potential as Fischer-Tropsch catalysts.     

以短链季铵盐/脂肪酸盐为模板合成超微孔二氧化硅

超微孔材料具有1~2 nm的孔径,在分离、催化应用中有望展现出择形催化的能力。 寻找经济、简便的合成超微孔材料的表面活性剂体系是一项有意义的工作。 本研究以短链季铵盐(十烷基三甲基溴化铵,记为C₁₀TAB)和不同链长脂肪酸酸盐混合胶束为模板剂,硅酸钠为硅源,成功制备出高度有序超微孔SiO₂。 通过小角X射线衍射、N₂吸附-脱附、傅里叶变换红外光谱、扫描电子显微镜(SEM)和透射电子显微镜(TEM)等技术手段对产品的结构和性能进行了表征。 结果表明,合成体系中脂肪酸盐碳链长、加入量、晶化温度等对产物孔道有序性有很大影响。 当选择正辛酸钠(SO)为助表面活性剂,当n(C₁₀TAB):n(Na₂SiO₃):n(SO):n(H₂O)=1:1.5:0.3:800,晶化温度为80 ℃时,可以得到高度有序超微孔SiO₂。 煅烧后样品比表面积为1300 m²/g,孔体积0.49 cm³/g,孔径分布在1.90 nm。     

Preparation and surface properties of low-density gels synthesized using prepolymerized silica precursors

Properties of silica xerogels and aerogels synthesized using a number of prepolymerized silica precursors were probed by 29Si magic-angle spinning (MAS) NMR spectroscopy, the small-angle X-ray scattering (SAXS) method, the nitrogen adsorption method, and transmission electron microscopy (TEM) to show that xerogels with attractive textural properties can easily be prepared using this type of precursors and the conventional one-step, base procedure. Pore sizes and overall pore volumes in these materials can be notably larger than those in the corresponding materials synthesized using tetraethoxysilane. This positive effect stems from the stronger structure of the polymeric network due to a higher degree of silica condensation on one side and a larger thickness of polymeric chains on the other. The thorough investigations of the fine silica structure demonstrate, however, that the relationship between the microstructure of the silica precursor and the micro- and macrostructures of dry gels is complex and the use of more condensed precursors favors, but does not necessarily ensure, more porous dry materials, under the same reaction conditions. Ethyl silicate 40 may be recommended as a low-cost precursor suitable for applications in this situation.     

Preparation of CuO/SiO<Subscript>2</Subscript> Hollow Spheres for Catalytic Oxidation of Phenol

Porous CuO/SiO₂ hollow microspheres were synthesized via an impregnation method using pure SiO₂ hollow microspheres as the supporter, and Cu species as the functional material. The hollow microspheres were characterized by X-ray diffraction, BET surface area, temperature-programmed reduction, transmission electron microscopy, and scanning electron microscopy. The catalytic activities of the CuO/SiO₂ hollow microspheres were investigated via the removal of the total chemical oxygen demand (COD) in the oxidation of phenol solution with air as an oxidant. The influence of various reaction parameters such as the reaction temperature, the partial pressure of O₂, and the initial pH of the solution were studied in detail. The coordination, dispersion and aggregation degree of copper species on porous materials play an important role for the COD removal of the phenol aqueous solution.     

Foaming behavior,cellular structure and physical properties of polybenzoxazine foams

In this paper, polymer foams based on a benzoxazine resin have been successfully prepared using azodicarbonamide (ADC) as a chemical blowing agent and have been characterized regarding their foaming behavior, cellular structure, and physical properties. The effect of the ADC on the curing process of the resin was analyzed using differential scanning calorimetry and blowing agent decomposition was followed by thermogravitmetric analysis (TGA). The characterization of the cellular structure of the foamed samples was done using scanning electron microscopy. The mechanical properties of the foams were determined using compression tests and the thermal conductivity was assessed using the transient plane source method. The results indicated that the curing process and gas release took place in a similar time interval. The foams showed an isotropic cellular structure with relative densities in the range 0.35–0.60, and showed compressive strengths and compressive moduli in the range of 10–70 MPa and 400–1100 MPa, respectively. Thermal conductivities were in the range of 0.06–0.12 W m^?1K^?1. The findings in this paper demonstrate the possibility of producing polybenzoxazine foams using a simple process in which curing and foaming take place simultaneously. In addition, the mechanical characterization of these materials indicates that they are suitable for structural applications. Copyright © 2011 John Wiley & Sons, Ltd.     

Morphology and Texture of Silica Prepared by Sol–Gel Synthesis on the Surface of Fibrous Carbon Materials

Silica materials are synthesized by the sol–gel method including the deposition of tetraethoxysilane on various micro- and nanocarbon fibers. The use of nanofibrous carbon as a template makes it possible to prepare thermally stable mesoporous SiO₂ samples with unusually high surface areas (up to 1255 m²/g) and high porosity (up to 5.6 cm³/g). These silica materials and aerogels prepared by supercritical drying have comparable pore volumes. It is found by high-resolution electron microscopy that a thin-wall matrix permeated by channels is a prevailing structure of silica materials. When some catalytic fibrous carbons are used as templates, silica nanotubes can be prepared.