Synthesis and Characterization of Mesoporous Silica Templated by Amphiphilic RTILs

This article reports a novel preparation of mesoporous silica with series of 1-alky-3-methylimidazolium bromide (C_nMIM)Br (n = 12, 14, 16), a kind of amphiphilic room-temperature ionic liquids (RTILs), as a template via a sol-gel nanocasting technique. The pore morphology and structures of these mesoporous silica were characterized by Transmission electron microscopy (TEM). The results show that the RTIL bearing longer alkyl chain is preferred to form the mesoporous silica material with bigger pores. (C₁₆MIM)Br has been chosen to study how the various influencing factors affect the synthesis and structure of the mesoporous silica material, such as the acid concentration, the solling time, the gelling time and the calcination time. N₂ adsorption-desorption isotherms measurement was used to characterize the pore size distribution and BET surface area. The results indicate that all of the factors can make an influence on the preparation of the mesoporous silica, which is more sensitive to the concentration of the acid.     

Tuning particle morphology of mesoporous silica nanoparticles for adsorption of dyes from aqueous solution

Spherical and rod mesoporous silica nanoparticles with hexagonal mesostructure were prepared using the modified Stöber method. The morphology, size and internal pore structure can be controlled by simple changing of surfactant concentration and water:ethanol molar ratio. Monodispersed spheroid MCM-41 was obtained at 40 °C under basic conditions using cetyltrimethylammonium bromide (C₁₆TAB) as template. Obtained materials were characterized by X-ray diffraction (XRD), nitrogen physisorption (BET), transmission electron microscopy (TEM) and scanning electronic microscopy (SEM). The results reveal that the pore volume and surface area increase when the amount of C₁₆TAB increases whereas the pore diameter and particle size decrease. However, the use of ethanol as cosolvent led to an increase in the particles’ size. Moreover, the addition of a 3-aminopropyltriethoxysilane greatly influenced the final particle shape. The material was effectively used for the removal of two fluorescent dyes (Hoechst 33342 and rhodamine 6g) from aqueous solution. Adsorption isotherm models, Langmuir, Freundlich and Temkin were used to simulate the equilibrium data. The Langmuir model was found to fit the experimental data better than others models.     

基于长链离子液体模板合成Fe(Co、Ni)-MCM-48

以两亲长链离子液体(氯化-1-十六烷基-3-甲基咪唑)为模板剂,采用水热合成方法,分别合成了含铁、钴和镍的立方介孔分子筛MCM-48。通过XRD、TEM、ICP-AES、FTIR、UV-Vis和N₂吸附/脱附实验对其结构和形态进行了表征,并考察了钴掺杂量和模板剂用量对合成立方相结构的影响。结果表明,用该方法合成的试样具有较高的比表面积和规则的立方介孔孔道结构等特征;相对于铁和镍的掺杂试样,钴物种能以四面体的结构稳定地存在于立方介孔分子筛骨架中。     

Fabrication and characterization of hexagonal mesoporous silica monolith via post-synthesized hydrothermal process

Large-sized, optical transparent mesostructured Brij 56/silica monolith has been fabricated using a lyotropic liquid crystal of Brij 56 (C₁₆EO₁₀) as a template and TMOS as a silica source, combined with a optimizing sol-gel process and a hydrothermal aging process. By programmed temperature drying and calcinations, translucent mesoporous silica monolith with two-dimensional hexagonal structure (P6mm) has bee obtained. The ordered mesoporous silica monoliths have been characterized by small-angle X-ray diffraction, transmission electron microscopy (TEM), and nitrogen adsorption, which shows that the materials have a highly ordered two-dimensional hexagonal mesostructure with the high specific surface area of 837 m² · g⁻¹ and narrow pore distribution with a mean BJH pore diameter of 2.73 nm. Based on calculations and differential scanning calorimetry and thermogravimetric analyses, the action mechanism of the hydrothermal aging process has been proposed: the 100°C hydrothermal conditions and autogenous 2.3 atm pressure promote the condensation and dehydration of silanol groups, with the result that cross-linking degree, the flaws and moisture content in gels are reduced notably. Those processes guarantee the integrity of gels in the following drying process.     

3D Hexagonal Mesoporous Silica and Its Organic Functionalization for High CO2 Uptake

Highly ordered 3D‐hexagonal mesoporous silica HMS‐3 and its vinyl‐ and 3‐chloropropyl‐functionalized analogues HMS‐4 and ‐5, respectively, are synthesized under strongly alkaline conditions at 277 K. Tetraethyl orthosilicate, vinyltrimethoxysilane, and 3‐chloropropyltrimethoxysilane are used as silica sources, and cetyltrimethylammonium bromide as the structure‐directing agent. The 3D‐hexagonal pore structures of HMS‐3, 4‐, and ‐5 were confirmed by powder XRD and high‐resolution TEM studies. Brunauer–Emmett–Teller surface areas of these materials are 1353, 1211, and 603 m² g^?1 for HMS‐3, ‐4, and ‐5, respectively. Among these materials, vinyl‐functionalized mesoporous material HMS‐4 adsorbs the highest CO₂ (5.5 mmol g^?1, 24.3 wt %) under 3 bar pressure at 273 K. The 3D‐hexagonal pore openings, very high surface area, and cagelike mesopores as well as organic functionalization could be responsible for very high CO₂ uptakes of these materials compared to other related mesoporous silica‐based materials.     

以卵磷脂为手性添加剂制备手性介孔二氧化硅

以十六烷基三甲基溴化铵(CTAB)的自组装体为模板,卵磷脂(PC)为手性添加剂,在n_PC:n_CTAB=1:21时,通过溶胶-凝胶法制备了螺旋介孔二氧化硅纳米棒。利用扫描电镜(FESEM)、透射电镜(TEM)、X-射线衍射以及氮气吸附-脱附等测试手段,对该纳米棒的形貌以及孔结构进行了表征。TEM显示该纳米棒的长度约为50~200nm,直径约为30~50nm。X-射线衍射表明孔道呈二维六方排列,虽然FESEM显示纳米棒左右手比例约为1:1,但通过圆二色谱表征证明该纳米棒在埃尺度下倾向于形成单一手性。结果表明,卵磷脂的手性可以传递到螺旋介孔二氧化硅纳米棒中。     

以卵磷脂为手性添加剂制备手性介孔二氧化硅

以十六烷基三甲基溴化铵(CTAB)的自组装体为模板,卵磷脂(PC)为手性添加剂,在n PC∶nCTAB=1∶21时,通过溶胶-凝胶法制备了螺旋介孔二氧化硅纳米棒。利用扫描电镜(FESEM)、透射电镜(TEM)、X-射线衍射以及氮气吸附-脱附等测试手段,对该纳米棒的形貌以及孔结构进行了表征。TEM显示该纳米棒的长度约为50～200 nm,直径约为30～50 nm。X-射线衍射表明孔道呈二维六方排列,虽然FESEM显示纳米棒左右手比例约为1∶1,但通过圆二色谱表征证明该纳米棒在埃尺度下倾向于形成单一手性。结果表明,卵磷脂的手性可以传递到螺旋介孔二氧化硅纳米棒中。     

Effect of two Kinds of Imidazolium Ionic Liquids on the Microemulsion Polymerization of Methyl methylacrylate

Summary: In this paper, the microemulsion polymerization of methyl methylacrylate (MMA) was carried out with single and gemini ionic liquids as emulsifier including 1-N-tetradecyl-3-methylimidazolium bromide (C₁₄MIM · Br) and 1, 4-Bis (3-tetradecylimidazolium-1-yl) butane bromide (C₁₄MIM-4-C₁₄MIM · 2Br) respectively, and they were all have typical microemulsion polymerization characters of MMA, but the process of polymerization directly depends on the structure of the imidazolium ionic liquids. The structure and concentration of ionic liquids have effects on the resulted latex particle sizes of PMMA, and much smaller size latexes of PMMA could be gotten with C₁₄MIM · Br as emulsifier than C₁₄MIM-4-C₁₄MIM · 2Br in polymerization. On the other hand, the structure of emulsifier has the effects on the molecular weight (MW) and molecular weight distribution (MWD) of PMMA, so the resulting PMMA prepared from microemulsion polymerization with C₁₄MIM · Br as emulsifier has higher MW but narrower MWD than that of PMMA with the same dosage of C₁₄MIM-4-C₁₄MIM · 2Br as emulsifier.     

多面体倍半硅氧烷制备有序介孔氧化硅材料

Octa(tetramethylammonium)-polyhedral oligomeric silsesquioxane(TMA-POSS) with cage-like structure was synthesized, the structure was characterized by NMR, FTIR and Elemental analyses. The mesoporous silica was prepared under alkaline condition using TMA-POSS as the silicon source and hexadecyltrimethylammonium bromide (CTAB) as the template, the structures of these products were characterized by XRD, TEM and nitrogen adsorption and desorption methods. The results indicate that the synthesized silica exhibites a well-ordered hexagonal pore structure with larger specific surface area. With increasing of CTAB molar ratio, the spacing of the crystal plane d100 is increased. The effects of the pH values on the mesoporous structure in the reaction system with different molar ratio of nPOSS / nCTAB were investigated. The synthesis mechanism of mesoporous silica was also discussed.     

Templated Synthesis of Ordered Mesoporous Carbons with Tailored Structures and Morphologies

Due to the excellent biocompatibility and the capability to load and release drugs, ordered mesoporous carbons (OMCs) have been highly prospective and valuable in drug delivery system. In this contribution, synthesis of OMCs with tailored pore sizes from 4.1 to 3.4 nm was achieved by employing SBA‐15 as template and furfuryl alcohol (FA) as carbon precursors. An array of OMCs with controlled structures and morphologies by incipient wetness with FA was analyzed by powder X‐ray diffraction (XRD), nitrogen adsorption, transmission electron microscopy (TEM), and Raman spectroscopy. The resulting carbon replicas retained the hexagonal symmetry of the silica templates SBA‐15 with p6mm space group, although the framework suffered shrinkage in the replicated process. The pore size distribution, uniformity and pore volume of the mesopores in the OMCs were affected by structural properties of the SBA‐15 templates as shown by N₂ sorption and XRD pattern analysis. The process had the advantage that the textural parameters of the obtained OMCs were tunable simply by varying aging temperature of the silica template and the ratio of carbon precursor.     

Synthesis of morphology-controllable mesoporous Co3O4 and CeO2

Recently, extensive works have been devoted to the morphology control of mesoporous materials with respect to their use in various applications. In this paper, we used two kinds of mesoporous silica, SBA-15 rods and spheres as hard templates to synthesize morphology-controllable mesoporous metal oxides. By carefully controlling the loading of metal precursors in the mesopores of the hard template, mesoporous Co₃O₄ and CeO₂ with different morphologies, such as micrometer-sized rod, hollow sphere, saucer-like sphere, and solid sphere were conveniently obtained. The structural properties of these materials were characterized by XRD, BET, SEM and TEM. In addition, it is found that the differences observed in the textural properties of the two mesoporous metal oxides nanocasted from the same template can be attributed to the properties of metal precursors and the interaction between metal oxide and SiO₂. Thus-obtained mesoporous metal oxides with such special morphologies may have a potential application in the field of environmental catalytic oxidation.     

以联二萘酚衍生物为手性添加剂制备介孔二氧化硅

通过溶胶-凝胶法以十八烷基三甲基溴化铵(STAB)自组装体为模板和非离子型联二萘酚衍生物(S)作为手性添加剂制备螺旋介孔二氧化硅。样品利用扫描电镜、透射电镜、X-光衍射以及氮气吸附-脱附进行了表征。结果表明:反应混合物中S与STAB的物质的量之比对介孔二氧化硅的形貌及孔结构有很大影响。改变nS∶nSTAB比,从0.1∶1到0.4∶1时,其结构从螺旋纳米棒状变为表面具有环形层状孔的纳米棒,孔道由沿着纳米棒长轴方向转变为同心环状。当nS∶nSTAB=0.5∶1时,得到类似皱缩花瓣的纳米颗粒。该手性添加剂的引入并没有改变左右手螺旋纳米棒的比例。     

以联二萘酚衍生物为手性添加剂制备介孔二氧化硅

通过溶胶-凝胶法以十八烷基三甲基溴化铵（STAB）自组装体为模板和非离子型联二萘酚衍生物（S）作为手性添加剂制备螺旋介孔二氧化硅。样品利用扫描电镜、透射电镜、X-光衍射以及氮气吸附-脱附进行了表征。结果表明：反应混合物中S与STAB的物质的量之比对介孔二氧化硅的形貌及孔结构有很大影响。改变n_S：n_STAB比,从0.1：1到0.4：1时,其结构从螺旋纳米棒状变为表面具有环形层状孔的纳米棒,孔道由沿着纳米棒长轴方向转变为同心环状。当n_S：n_STAB=0.5：1时,得到类似皱缩花瓣的纳米颗粒。该手性添加剂的引入并没有改变左右手螺旋纳米棒的比例。     

介孔氧化硅孔径尺寸对Eu(Ⅲ)配合物的影响

分别以十六烷基三甲基溴化铵(CTAB)和聚乙氧基-聚丙氧基-聚乙氧基三嵌段共聚物(P123)为模板剂、正硅酸乙酯(TEOS)为硅源，采用水热法合成了有序介孔分子筛MCM-41和SBA-15。选择Eu(DBM)₃phen为客体，有序介孔氧化硅MCM-41和SBA-15为载体，分别在氯仿中进行分子组装，制备出具有较强发光性能的介孔复合材料Eu(DBM)₃phen/APTES-MCM-41(EAM)和Eu(DBM)₃phen/APTES-SBA-15(EAS)。采用XRD、TEM、N₂吸附-脱附和荧光光谱等对产物的结构与性能进行了分析。结果表明，Eu(DBM)₃phen组装进有序介孔氧化硅的孔道中后，发光纯度提高。而且孔径越小，发光纯度越高。选用较大孔径的SBA-15为载体，在不显著影响发光纯度的同时，可以获得较高的发光强度。     

Needle-like calcium carbonate assisted self-assembly of mesostructured hollow silica nanotubes

Mesostructured hollow silica nanotubes (MHSNTs) were successfully produced via the self-assembly of C₁₆TMABr and silica species on the surface of needle-like calcium carbonate nanoparticles in an alkaline medium at room temperature. The characterization of MHSNTs by transmission electron microscopy (TEM), scanning electron microscopy (SEM), pore size distribution (PSD) and Brunauer-Emmett-Teller (BET) indicated that MHSNTs had uniform tubular hollow structures with big openings, a length of 1.5-2.0 μm, an inner diameter of 150-200 nm at the open end and 50-60 nm at the closed end, and a wall thickness of 20-30 nm, as well as a narrow PSD around 2.3 nm in the shells and a BET surface area as high as ∼975.3 m²/g. By small-angle X-ray diffraction (XRD), BET and pore structure analysis, it was found that more uniformly structured mesopores could be formed by the method of removing the double templates simultaneously through a solvent extraction process, as compared to the separate removal of the double templates by calcinating and then etching in an acidic solution, and the amount of C₁₆TMABr affected the mesoporous structures of MHSNTs greatly. The formation processes of MHSNTs were also studied with XRD and FTIR.     

介孔SiO2的改性及对诺维信漆酶的交联固定化

采用十六烷基三甲基溴化铵(CTAB)为模板剂,四乙氧基硅烷(正硅酸乙酯,TEOS)为硅源,硝酸为催化剂来制备介孔SiO2,并采用后嫁接法对介孔SiO2进行氨基化改性。利用红外光谱(IR),X射线粉末衍射(XRD),差热-热重分析(DTA-TG),扫描电镜(SEM),元素分析,微电泳法及N2吸附-脱附方法对改性前后的产物进行表征。结果表明氨基已成功嫁接到介孔SiO2孔道中,改性后的介孔SiO2有序度有所下降,但仍为介孔材料;改性之后介孔材料的孔径、比表面积、孔体积均变小。等电点由原来的2.74变为4.75。本文还以氨基修饰的介孔SiO2为载体,通过交联剂戊二醛固定诺维信(Novozymes)工业级漆酶,并采用正交设计法对固定化条件进行了优化。研究表明漆酶经固定化后,其操作稳定性比游离酶高。     

Preparation of a kind of mesoporous carbon and its performance in adsorptive desulfurization

Carbon materials were prepared using mesoporous silica HMS with different pore sizes as the hard templates and water-soluble phenolic resin as the carbon source. The obtained materials were characterized by powder X-ray diffraction, transmission electron microscopy and N₂ physical adsorption, and were used in adsorptive desulfurization. It has been shown that the carbon material prepared using HMS with larger pore size (>3 nm) presented uniform wormlike mesopore of 2.3 nm and large BET surface area (1903 m²/g). The mesoporous carbon was an excellent adsorbent to remove the refractory sulfur compound in diesel, especially dibenzothiophene and 4, 6-dimethyldibenzothiophene.     

Periodic Mesoporous Organosilicas with Helical and Concentric Circular Pore Architectures

This study systematically investigates periodic mesoporous organosilicas (PMOs) with controlled helical and concentric circular (CC) pore architectures prepared through a basic‐catalyzed sol–gel process by using an achiral cationic surfactant trimethyloctadecylammonium bromide (C₁₈TAB) as a structure‐directing agent, perfluorooctanoic acid (PFOA) as an additive, and 1,2‐bis(triethoxysilyl)ethane (BTEE) as a hybrid silica precursor. By increasing the weight ratio of PFOA/C₁₈TAB, a pore architecture transition of PMO materials from hexagonal‐arrayed, straight longitudinal channels to helical and CC mesostructures is achieved; such a transition has not been observed before in PMO materials. Our discovery is helpful in understanding the supramolecular cooperative assembly of hybrid materials and their structural and morphological evolution, which are important in the future applications of PMO materials.     

Influence of the Template Removal Method on the Mechanical Stability of SBA-15

Removing the template from the pores after the polycondensation of the silica precursor is a necessary step in the synthesis of mesoporous silica materials. In our previous work, we developed a method for the efficient and spatially controlled functionalization of SBA-15. First, the silanol groups on the particle surface and in the pore entrances were passivated. After extraction of the template, a pretreatment step in N₂ converted the silanol groups to the single and geminal state. Afterwards, an azide functionality was introduced exclusively into the mesopores. This ensured that the catalyst could afterwards be immobilized unambiguously in the mesopores. The mechanical stability of a material functionalized in such a spatially controlled manner is studied and compared to other template removal methods. Even though several studies investigated the influence of the calcination temperature, the presence or the absence of oxygen during the template removal, the specific conditions used during the herein reported selective functionalization procedure have not been covered yet.     

Physicochemical features of the formation of siliceous porous mesophases

The formation of siliceous mesoporous mesophase materials (SiO₂-MMM) prepared by precipitation of soluble forms of SiO₂ with alkyltrimethylalkylammonium bromide C _n TMABr (n=12, 14, 16, 18 is the number of carbon atoms in the alkyl chain) was investigated. An increase in then value has no influence on the mechanism of formation of SiO₂-MMM but causes an increase in the size and volume of mesopores with the mesopore specific surface area and wall thickness remaining virtually constant.