不同形貌SBA-15的控制合成及应用

介绍了近几年来不同形貌SBA-15材料的设计组装过程,叙述了在非离子嵌段共聚物模板剂下,陈化温度、搅拌速率、共表面活性剂和无机盐等因素对SBA-15介孔材料形貌的影响,及其合成机理。介绍了不同形貌SBA-15材料的应用现状。认为不同形貌的SBA-15介孔材料对催化、吸附分离等反应具有不同的影响,但是对于每一种反应,总有一种形貌的SBA-15的反应性能是最佳的;为使机械性能和水热稳定性能优良的具有二维六方介孔结构的SBA-15材料能更好地应用于各领域,继续研究不同形貌的SBA-15的设计组装过程对催化、吸附分离和燃料电池等领域具有深远的意义。     

Al掺杂SBA-15介孔材料的合成与吸附性能研究

采用两步水热法合成了Al掺杂SBA-15介孔分子筛,并且用XRD、SEM、N2吸附与UV-Vis对所合成的样品进行表征。考察了Al掺杂SBA-15介孔分子筛的有序度、表面形貌、比表面积、Si/Al比以及对亚甲基蓝吸附性能的影响。结果表明:介孔材料保持了完好的二维六方介孔结构,表面形貌无变化,比表面积减小,铝元素均匀地掺杂于SBA-15的骨架当中,Si/Al约为21. 4; Al掺杂SBA-15对水溶液中的亚甲基蓝展现出良好的吸附性能,在15min内,吸附率达96%。     

介孔材料的制备与应用进展

综述了模板法、水热法、溶胶-凝胶法、溶剂热法、超声化学法及反胶束法等制备介孔材料的方法,其中模板法介绍了阳离子表面活性剂、阴离子表面活性剂、非离子表面活性剂、混合表面活性剂以及非表面活性剂等作为模板剂在介孔材料制备中的应用.评述了介孔材料的几种典型形貌,并对介孔材料在催化、吸附分离、传感器电极材料的制备以及酶的固定与分离等领域的应用进行了简要介绍.     

SBA-15形貌对聚乳酸微孔发泡的影响

文章采用水热法合成了球状、棒状与环状三种形貌的SBA-15无机介孔粒子,利用含氟硅烷对粒子进行亲二氧化碳修饰后,用于聚乳酸超临界二氧化碳(scCO2)微孔发泡,探索了粒子形貌对聚乳酸发泡材料的泡孔结构的影响。TG,BET和SEM等分析表明,不同粒子形貌的介孔粒子具有不同的硅烷接枝率,在聚乳酸微孔发泡材料中异相成核作用也不同,就泡孔尺寸和泡孔密度来讲,环状SBA-15粒子对聚乳酸发泡的异相成核作用最好,表明介孔粒子有望成为新型的微孔发泡成核剂。     

V/SBA-15的水热合成法制备及其催化氧化性能研究

为了制备负载型介孔分子筛V/SBA-15并研究其在乙苯制苯乙酮反应中的催化性能,以P123(三嵌段共聚物)为模板剂,正硅酸乙酯为硅源,柠檬酸氧钒配合物为前驱体,在酸性条件下采用水热法一步合成了V/SBA-15有序介孔材料,利用XRD,BET,FT-IR等手段对所合成的V/SBA-15材料进行了结构表征,并在乙苯制苯乙酮反应中以苯乙酮选择性和收率来验证催化剂的催化性能。实验结果表明:此合成材料具有类似于SBA-15的高度有序的六方介孔结构,活性组分钒均匀分散在介孔氧化硅基体中;在催化氧化乙苯制苯乙酮反应的优化条件下,苯乙酮选择性和收率分别为80.87%,35.26%。     

晶化温度对介孔材料SBA-15结构与形貌的影响

以P123嵌段共聚物表面活性剂为模板剂,在不同晶化温度下合成了不同孔径和比表面积的六方相介孔氧化硅SBA-15,通过XRD, SEM, N2吸附-脱附及TEM等手段系统考察了不同晶化温度对SBA-15晶胞参数、比表面积、孔径及形貌的影响,得到反应最佳晶化温度为120℃. 随着晶化温度的升高,SBA-15的孔径增大,比表面积下降,团聚体颗粒打开形成散落短棒状. 同时还对温度影响SBA-15结构和形貌的机理进行了探讨.     

粒径对磺酸官能化介孔材料性能的影响

以聚乙氧基-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,保持P123和TEOS的浓度比,改变P123和TEOS在合成体系中的浓度,水热法合成了系列具有不同粒径的介孔分子筛SBA-15.采用后合成法,将3-巯基丙摹三甲氧基硅烷(MPTMS)嫁接到具有不同粒径的介孔分子筛SBA-15表面上,经氧化后得到含有强酸性的磺酸基因的固体酸样品SBA-15-SO_3H.采用SEM、XRD、FT-IR、TG-DTA、N_2吸附以及酯化反应考察了粒径对所制备的SBA-15-SO_3H的物化性能和催化性能的影响.结果表明,SBA-15的粒径大小对MPTMS在其上的嫁接量没有很人影响,但对后续氧化过程有较大的影响,SBA-15粒径的减小有利于巯基被氧化为磺酸基,导致磺酸的负载量随着粒径的减少而增大.SBA-15-SO_3H在乙酸和乙醇的酯化反应中表现出不同的催化性能,催化性能的差异是粒径大小、酸量及磺酸基和巯基相互作用的综合结果.     

ZnO改性复合材料的制备及其光谱性质鉴定

以正硅酸乙酯(TEOS)为硅源,采用水热法制备出MCM-41和SBA-15介孔材料;然后以介孔材料为主体、ZnO(氧化锌)为客体,采用锌盐浸渍-灼烧法使介孔材料负载ZnO微粒,制得功能性ZnO/MCM-41、ZnO/SBA-15复合材料,并采用X-射线衍射(XRD)、N2吸附-脱附和荧光光谱法等对复合材料的结构和性能进行了表征。研究结果表明:ZnO已成功进入介孔材料中,并且均未改变主体原有的二维六方形孔道结构,只是有序程度有一定的下降;该复合材料在400nm左右出现相对最强的吸收峰。     

Cu2O负载SBA-15的合成与表征

利用Vc一步还原的策略合成了Cu_2O负载的SBA-15有序介孔材料。利用XRD、SEM与UV-vis等对Cu_2O负载SBA-15介孔材料进行了表征。研究了乙酸铜加入量对SBA-15介孔材料的有序度、表面形貌和Cu_2O纳米晶体负载量的影响,以及Cu_2O负载SBA-15对甲基橙的催化性能。结果表明:介孔材料保持了完好的二维六方介观结构,随着乙酸铜加入量增加,Cu_2O纳米晶体负载量增多;Cu_2O负载SBA-15对水溶液中的甲基橙展现出良好的催化氧化性能,在25min内,降解率达到100%。     

磺酸基功能化的介孔材料HSO_3-Zr-La-SBA-15的制备

介孔材料具有孔道结构规则有序、孔径均匀且可调、比表面积高、形貌可控、表面可功能化等特点,在大分子吸附、分离,特别是催化等领域有着重要的应用前景。在没有加任何无机酸的情况下,水热法一步制备了双金属掺杂的介孔材料Zr-La-SBA-15(ZLS),接着以3-巯丙基-三甲氧基硅烷为有机功能试剂,通过采用后接枝法合成了磺酸基功能化的介孔材料HSO3-ZLS,并通过小角X-射线衍射(SXRD)、氮气吸附-脱附、红外光谱、透射电镜和热重等分析方法进行了详细表征。结果表明,修饰后的样品依然保持了SBA-15有序二维六方相介孔结构,且具有比表面及孔容较大、孔径分布较窄、热稳定性较高等优点。     

Phase transition of mesoporous SiO<Subscript>2</Subscript> impregnated with an organic templating agent by post-synthetic microwave heating

Mesoporous silica SBA-15 samples were subjected to microwave heating for 10–40 min at 393 and 443 K after dry-impregnation with TPAOH (tetrapropylammonium hydroxide) to prepare a mesoporous material with zeolytically ordered pore walls. Physicochemical properties of the materials prepared were characterized by XRD, N₂ adsorption at 77 K, SEM, TEM, UV–vis and FT-IR spectroscopies. These investigations revealed that selective transformation of amorphous pore walls of SBA-15 to crystalline zeolytic phase is difficult to be achieved and a mixed phase of mesoporous silica/zeolite composite material was obtained, instead. Microwave heating time, temperature, TPAOH concentration, and hydrothermal stability of the mesoporous host materials tested (MCM-41, HMS, and SBA-15) were important factors to maintain the mesopore structure of the host materials during the post-synthetic microwave heating treatment.     

Simultaneous control of rod length and pore diameter of SBA-15 for PPL loading

Mesoporous silica materials are attractive materials for immobilizing enzymes because of their well-ordered structures, large surface area are pore volume. Diffusion of large enzyme molecules such as porcine pancreatic lipase (PPL) through the lengthy channels of MPS takes place too slowly. Therefore, the squat of the enzyme at the pore mouth entrance, actually makes the rest of the channel useless. In this study, to overcome this problem, synthesis parameters of SBA-15 were changed, since along with pore diameter increasing, the mesochannel length becomes shorter. The main point to obtain a well-ordered 2D hexagonal pore structure was the pre-hydrolysis of tetraethyl orthosilicate (TEOS) before the addition of 1,3,5-trimethyl benzene as a micelle swelling agent. Due to the strong effect of zirconium in changing the morphology of SBA-15 particles, we modified SBA-15 in the presence of a small amount of ZrOCl₂ in the synthesis solution under acidic conditions. As a result, mesochannel length of SBA-15-Zr was shortened from 600 to <200 nm. The morphology of mesoporous silica was also changed from rod-like to platelet, because of the accelerating effect of Zr(IV) on the self-assembly rate of P123 and TEOS condensation. Characteristic results conducted by low angle XRD, high resolution transmission electron microscopy and nitrogen adsorption, confirmed tuning effect of Zr(IV) in SBA-15. Furthermore, it was shown that the number of pore entrances increases with decreasing the length of SBA-15 mesochannels, leading to obvious improvement of enzyme uptake. PPL has been successfully immobilized in the mesoporous channels of SBA-15-Zr. The total amount of lipase adsorbed on the mesoporous SBA-15-Zr was measured by thermal gravimetric analysis. The largest PPL adsorption capacity was 784 mg/g belonging to the SBA-15-Zr with the length of 150 nm and the mean pore size diameter of 9.22 nm.     

Carbon-coated mesoporous silica with hydrophobicity and electrical conductivity

The pore surface of mesoporous silica SBA-15 was coated with 2,3-dihydroxynaphthalene (DN) through a dehydration reaction between the surface silanol groups in SBA-15 and the hydroxyl groups of the DN molecules. By the carbonization of DN in the SBA-15 pores, the pore surface was uniformly covered with an extremely thin carbon layer, which comprised only 1-2 graphene sheets. The resulting carbon-coated SBA-15 still possessed the characteristics of the original SBA-15—large surface area and pore volume, long-range ordered structure, and sharp mesopore size distribution. In addition, the carbon-coated SBA-15 showed marked hydrophobicity and high electrical conductivity, both of which are not intrinsic properties of SBA-15. The appearance of these features can be explained from the almost perfect carbon coating on the pore surface. Newly developed graphene coating technique can donate characteristic carbon properties to mesoporous silica.     

Trypsin immobilization on mesoporous silica with or without thiol functionalization

The effects of pore size, structure, and surface functionalization of mesoporous silica on the catalytic activity of the supported enzyme, trypsin, were investigated. For this purpose, SBA-15 with 1-dimensional pore arrangement and cubic Ia3d mesoporous silica with 3-dimensional pores were prepared and tested as a support. Materials with varying pore diameters in the range 5–10 nm were synthesized using a non-ionic block copolymer by controlling the synthesis temperature. Thiol-group was introduced to the porous materials via siloxypropane tethering either by post synthesis grafting or by direct synthesis. These materials were characterized using XRD, SEM, TEM, N₂ adsorption, and elemental analysis. Trypsin-supported on the solids prepared was active and stable for hydrolysis of N-α-benzoyl-DL-arginine-4-nitroanilide (BAPNA). Without applying thiol-functionalization, cubic Ia3d mesoporous silica with ca. 5.4 nm average pore diameter was found to be superior to SBA-15 for trypsin immobilization and showed a better catalytic performance. However, enzyme immobilized on the 5% thiol-functionalized SBA-15 prepared by directly synthesis was found to be the most promising and was also found recyclable.     

A biomimetic mesoporous silica–polymer composite scaffold for bone tissue engineering

A biomimetic organic–inorganic composite system comprising of microspheres fabricated from combination of a biodegradable polymer poly(lactide-co-glycolide) (PLGA) and bioactive mesoporous silica (SBA-15) has been developed through sintering technique for bone regeneration applications. The morphological and structural properties of the SBA-15/PLGA composite scaffold were evaluated using electron microscopy and fourier transform infrared spectroscopy and the results showed spherical morphology and composite nature. The presence of mesopores in the silica was confirmed through nitrogen adsorption–desorption isotherms. The surface area and pore size of mesoporous silica were found to be 792 m² g^?1 and 3.7 nm, respectively. The thermal characteristics of the SBA-15/PLGA composites studied using thermogravimetry analysis shows a weight loss of around 80% with the degradation occurring at 324?°C. The prepared scaffold is also found to support the adhesion and proliferation of osteoblast cells. The expression of specific bone markers is significantly enhanced in the SBA-15/PLGA composite scaffold when compared with the pristine polymeric scaffold indicating the positive effect of mesoporous silica. Hence, these SBA-15/PLGA composite scaffolds can be explored further for bone regeneration applications.     

Synthesis of Ti-containing SBA-15 materials and studies on their photocatalytic decomposition of orange II

Titanium substituted SBA-15 mesoporous materials have been successfully prepared by conventional hydrothermal method and they were also used as support on TiO₂ loaded SBA-15 photocatalysts. The synthesized materials were characterized by XRD, UV–vis DRS, FT-IR, BET and TEM. We also examined the activity of these materials as photocatalysts for the decomposition of orange II. The incorporation of titanium into framework of SBA-15 makes the pore diameter and pore volume to decrease and slightly decreases the surface area compared to SBA-15. In addition, the pore size distribution becomes broaden with an increase of titanium amount in the SBA-15 framework. For Ti-SBA-15 and TiO₂ loaded Ti-SBA-15 photocatalysts, the IR absorption at 960 cm⁻¹ commonly accepted the characteristic vibration of Ti–O–Si bond. From the TEM images, the regular silica morphology is maintained in the case of Ti-SBA-15(Si/Ti = 50) but the Ti-SBA-15 sample having Si/Ti ratio = 10 partially destroys the hexagonal highly ordered structure and the mesopore structure is disappeared by the clogging of mesopore channels by the titanium dioxides particles for the 50 wt.% TiO₂/Ti-SBA-15 samples. The photocatalytic activity increases with an increase of Ti content (decrease of Si/Ti ratio) and with an increase of TiO₂ loading content.     

Morphological control of mesoporous silica SBA-15 synthesized at low temperature without additives

Fiber-like or rod-like mesoporous SBA-15 silicas with different lengths and diameter of macrostructures and pore diameter could be synthesized by the self-assembly of silica-surfactant (commonly used Pluronic P123 (EO₂₀-PO₇₀EO₂₀) as a structure-directing agent) through careful control of the synthetic temperature and stirring time without any additives. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and nitrogen adsorption–desorption isotherms are used to characterize these mesoporous silica materials. Compared with those reports on conventional SBA-15, our work is focused on one-step synthesis and the morphological control of ordered mesoporous silica synthesized at low temperature under low concentration of P123 (0.67 wt%) without the addition of inorganic salts, where pre-hydrolyzed silica species may favor the self-assembly of silica-polymer hybrid micelles. Moreover, the pore diameter of fiber-like SBA-15 synthesized at 40 °C is slightly smaller than that of conventional SBA-15, revealing that the average micellar radius of P123 micelles in this low concentration of P123 solution was almost same as that for the conventional synthesis of SBA-15.     

Controlling the textural parameters of mesoporous carbon materials

The mesoporous carbon materials prepared by inorganic templating technique using mesoporous silica, SBA-15 as a template and sucrose as a carbon source, have been systematically investigated as a function of sucrose to mesoporous silica composition, with a special focus on controlling the mesoporous structure, surface morphology and the textural parameters such as specific surface area, specific pore volume and pore size distribution. All the materials have been unambiguously characterized by XRD, N₂ adsorption–desorption isotherms, high-resolution transmission electron microscopy, high-resolution field emission scanning electron microscopy, and Raman spectroscopy. It has been found that the porous structure, morphology and the textural parameters of the mesoporous carbons materials, CMK-3-x where x represent the sucrose to silica weight ratio, can be easily controlled by the simple adjustment of concentration of sucrose molecules. It has also been found that the specific surface area of the mesoporous carbon materials systematically increases with decreasing the sucrose to silica weight ratio. Moreover, the specific pore volume of the materials increases from 0.57 to 1.31 cm³/g with decreasing the sucrose to silica weight ratio from 5 to 1.25 and then decreases to 1.23 cm³/g for CMK-3-0.8. HRTEM and HR-FESEM also show a highly ordered pore structure and better surface morphology for CMK-3-1.25 as compared to other materials prepared in this study. Thus, it can be concluded that the sucrose to silica weight ratio of 1.25 is the best condition to prepare well ordered mesoporous carbon materials with good textural parameters, pore structure and narrow pore size distribution.     

Control of ordered structure and morphology of cubic mesoporous silica SBA-1 via direct synthesis of thiol-functionalization

Well-ordered cubic mesoporous silicas SBA-1 functionalized with thiol groups have been synthesized via co-condensation of tetraethoxysilane (TEOS) and 3-mercaptopropyltrimethoxysilane (MPTMS) templated by cetyltriethylammonium bromide (CTEABr) under strongly acidic conditions. Various synthesis parameters such as HCl concentration, synthesis temperature, and time for hydrothermal treatment were systematically investigated as a function of MPTMS contents. The materials thus obtained were characterized by a variety of techniques including powder X-ray diffraction (XRD), solid-state ¹³C and ²⁹Si NMR spectroscopy, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and nitrogen sorption measurements. Direct evidence of the presence of chemically attached thiol moieties was provided by solid-state ²⁹Si and ¹³C NMR spectroscopy. A high degree of structural ordering was still retained when MPTMS loading was incorporated up to 20 mol% in the synthesis mixture. Increasing the synthesis temperature and the time for the hydrothermal treatment not only increased the degree of framework cross-linking, but also did not lead to the undesirable phase transformation as often observed in the conventional synthesis of pure silica SBA-1. SEM results reveal that the morphology of thiol-functionalized SBA-1 depends on the HCl concentration used in the synthesis. The sample prepared with a low acid concentration exhibits a highly isotropic morphology with more facets than that of pure silica SBA-1, whereas it changes to a spherical shape as the acid concentration is increased. The maximum content of the attached thiol group (–SH) in the mesoporous framework is 2.39 mmol/g. The thiol-functionalized SBA-1 mesoporous materials are efficient Hg²⁺ adsorbents.     

Trypsin immobilization on mesoporous silica with or without thiol functionalization

The effects of pore size, structure, and surface functionalization of mesoporous silica on the catalytic activity of the supported enzyme, trypsin, were investigated. For this purpose, SBA-15 with 1-dimensional pore arrangement and cubic Ia3d mesoporous silica with 3-dimensional pores were prepared and tested as a support. Materials with varying pore diameters in the range 5–10 nm were synthesized using a non-ionic block copolymer by controlling the synthesis temperature. Thiol-group was introduced to the porous materials via siloxypropane tethering either by post synthesis grafting or by direct synthesis. These materials were characterized using XRD, SEM, TEM, N₂ adsorption, and elemental analysis. Trypsin-supported on the solids prepared was active and stable for hydrolysis of N-α-benzoyl-DL-arginine-4-nitroanilide (BAPNA). Without applying thiol-functionalization, cubic Ia3d mesoporous silica with ca. 5.4 nm average pore diameter was found to be superior to SBA-15 for trypsin immobilization and showed a better catalytic performance. However, enzyme immobilized on the 5% thiol-functionalized SBA-15 prepared by directly synthesis was found to be the most promising and was also found recyclable.