Ordered Mesoporous Silica as Supports in the Heterogeneous Asymmetric Catalysis

Enantioselective synthesis of organic compounds has been studied by homogeneous catalysts for several years. However, these catalysts have yet to make a significant impact on industrial scales for fine chemical synthesis. A primary reason is the designing of a homogeneous asymmetric catalyst, which requires relatively bulky ligands and catalyst recovery and recycling often causes problems. One of the convincing ways to overcome this problem is to immobilise the asymmetric catalyst onto a solid support and the resulting heterogeneous asymmetric catalyst system can, in principle, be readily re-used. A large number of supports such as inorganic oxides including zeolites, alumina, zirconia, silica and organic polymers have been employed as supports in heterogeneous asymmetric catalysis. Therefore, in this review article we have summarized the work done by us in our laboratory on the immobilization of chiral transition metal complexes such as Ru, Ir, Mn and Ti onto ordered mesoporous silica and its asymmetric catalysis. All these immobilized catalysts were well characterized by different physicochemical techniques to confirm the structural retention of the support as well as the active metal complex after immobilization. This report includes our asymmetric catalytic investigations in enantioselective reactions such as hydrogenation of ketones, olefins, oxidation of sulfides and oxidative kinetic resolution of alcohols and sulfoxides through immobilized heterogeneous catalyst systems.     

有序介孔硅材料主-客体组装及应用研究

介孔分子筛材料具有高的比表面积和孔体积、发达的孔结构、可控的形貌、表面基团可功能化、耐热、无毒无害等特点,以其为研究核心,在学术界和工业界均具有广泛的应用前景。通过模板法合成孔径在纳米范围的有序介孔硅材料,其具有从一维到三维高度规整的孔道结构,在吸附、分离、催化、生物医药工程等领域展现出巨大的应用潜能。利用具有几何和电子束缚特性的有序规整孔道作为微反应器来进行纳米结构主-客体组装,势必会显著增强其应用价值。本文以有序介孔硅材料规整孔道为基础和出发点,结合本课题组多年的研究结果,系统概述了近几年客体在有序介孔硅材料孔道内组装的进展,探讨了主-客体组装过程中的影响因素和合成机理。最后,着重对主-客体组装材料在环境净化和生物医药工程领域的应用进行概述。     

模板法合成六方介孔SiO2

模板法合成六方介孔SiO2;六方结构;低聚表面活性剂     

酸诱导介观相转变硅基介孔材料的合成机理及其改性

采用两步法以三嵌段共聚物P104(PEO27-PPO61-PEO27)为模板剂合成介孔材料, 研究了介孔材料结构随体系pH 值的变化, 探讨了体系中介观相转变的机理. 研究表明,随着pH 的升高, 发现体系中无机物种和模板剂所组成的介观相发生了转变,由P6mm 的SBA-15(pH=1.51-2.67)2D六角孔道结构转变为3D 蠕虫状孔道的MSU-X(pH=3.93-4.56)结构. 对所得的两种不同种类的硅基材料以γ-胺丙基三乙氧基硅烷(APTES: NH2(CH2)3Si(C2H5O)3)进行表面烷基化改性结果表明, 在同样的条件下, 经过改性后MSU-X类介孔材料孔壁上接枝的烷基数目要远超过SBA-15 类介孔材料.     

"面包圈"状高有序度大孔径介孔分子筛SBA-15的合成

介孔材料因其高度有序的大孔径、较佳的催化吸附性能、良好的电磁性质及易于剪裁而引起人们极大的兴趣[1～9].人们已相继合成了介孔氧化硅薄膜[3,10]、球[12]、空心球[4,13]和纤维[12～15]等,并设法控制中孔材料晶体外貌[3～9,15～21].最近,我们报道了利用多相组装和无机晶体(如NaCl,LiCl)作大孔结构导向剂的方法[16],合成了人造"珊瑚"状介-大孔氧化硅膜[13].Lin等[17]用共表面活性剂法在丁醇存在下合成了多组有序结构的介孔氧化硅空心球; Shio等[21]在完全溶解的硅酸钠和阳离子表面活性剂溶液中,合成了细棒状介孔氧化硅粉末.本文报道一种控制介孔材料颗粒外貌和形状的新方法,即共溶剂法,并以此法合成了高有序度、大孔径、 "面包圈"状介孔氧化硅SBA-15.这种新材料有望在微加工、催化、生物分离、电子器件的矿化、色谱载体等方面得到应用[1～9].     

Synthesis of Highly ordered Large Size Mesoporous Silica and Effect of Stabilization as Enzyme Supports in Organic Solvent

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Adsorption Isotherm of Water Vapor and Its Large Hysteresis on Highly Ordered Mesoporous Silica

The first and second adsorption–desorption isotherms of water vapor on a new mesoporous material derived from kanemite have been measured. The isotherms show unusual type V isotherms and large hysteresis. The type V isotherms, which have never been observed for the other adsorbates, suggest that the mesoporous material has a hydrophobic surface, although the hydrophobicity decreased after treatment with water vapor because of rehydration of the surface. The significantly large hysteresis could be explained by the difference in contact angle between adsorption and desorption.     

疏水性有序介孔氧化硅薄膜的制备

采用溶胶−凝胶技术并结合蒸发诱导自组装工艺, 以三嵌段共聚物EO₂₀PO₇₀EO₂₀ (P123)为模板剂, 使用浸渍提拉法制备了有序介孔氧化硅薄膜, 并使用不同的表面修饰剂对薄膜进行表面处理, 制备了疏水性有序介孔氧化硅薄膜. 利用FT-IR、小角XRD、HRTEM分别表征薄膜的化学物种和孔结构, 探讨了热处理温度和老化时间对薄膜介孔结构的影响, 通过接触角测试研究薄膜的疏水性能, 考察了修饰剂种类、修饰浓度和修饰时间对薄膜疏水性的影响, 结果表明所制备的薄膜为高度有序的介孔氧化硅薄膜, 孔径大小约为8 nm|表面修饰对薄膜的有序性有一定影响, 经三甲基氯硅烷(TMCS)和g-氨丙基三乙氧基硅烷(KH-550)修饰后的薄膜具有很好的疏水性能, 接触角分别为112°和96°|修饰后薄膜的水汽稳定性良好, 仍能保持有序介孔结构, 孔径达7.5 nm, 接触角达93°.     

有序介孔硅片粒子表面的修饰及其表征

采用溶胶-凝胶的方法制备了粒径在50~300nm,具有正六边形的介孔二氧化硅片,用1,6-己二异氰酸酯(hexamethylene diisocyanate,HDI)对有序介孔硅片粒子表面进行有机化修饰,使其表面接枝能够参与反应的N=C=O活性基团。用FTIR、热重分析、TEM等分析方法对修饰后的有序介孔硅片粒子进行了表征,以确定HDI接在了有序介孔硅片粒子的表面。     

三头季铵盐表面活性剂导向合成新型立方相介孔二氧化硅

介孔分子筛因具有大而均一的孔道、高比表面积及相对良好的热稳定性而在精细化学品催化剂[1,2 ] 、生物大分子分离 [3] 和功能材料的主体 [4 ] 等领域有十分广阔的应用前景 .自 1 992年 Mobil公司合成 M41 S[5,6 ] 系列介孔材料以来 ,HMS[7] ,MSU[8] 和 SBA[9～ 12 ] 系列以及 FDU- 1 [13] 等不同结构的介孔分子筛材料相继被合成 .立方相介孔分子筛因具有三维网状结构和可通性较高的孔道而在反应中不易堵塞 ,相对于一维孔道结构的六角相 MCM- 41和 SBA- 1 5 ,其应用前途更加广阔 .迄今 ,人们已经合成了 MCM- 48[14～ 16 ]( Ia3d) …     

有序介孔二氧化硅对正丁醛的吸附性能

合成了一系列具有不同孔结构与性质的有序介孔二氧化硅材料SBA-15、MCM-41、SBA-16、KIT-6, 同时通过改变水热温度制备了不同孔径大小的SBA-15, 并利用小角X射线散射、透射电镜、扫描电镜和氮气吸附-脱附等手段, 对其介孔结构进行了表征. 以正丁醛为探针分子, 考察了其对有机醛的吸附, 并与Y-沸石的吸附性能做了对比. 结果表明, 材料的介孔比表面积与其对正丁醛的吸附量成正比, 吸附等温线符合Langmuir 模型, 属于单层吸附, 具有最大介孔比表面积的MCM-41对正丁醛的吸附量最大(484 mg·g^-1). 最后将SBA-15添加到卷烟滤嘴中, 实验结果表明, SBA-15能显著降低卷烟烟气中巴豆醛的释放量.     

有序介孔二氧化硅对正丁醛的吸附性能

合成了一系列具有不同孔结构与性质的有序介孔二氧化硅材料SBA-15、MCM-41、SBA-16、KIT-6,同时通过改变水热温度制备了不同孔径大小的SBA-15,并利用小角X射线散射、透射电镜、扫描电镜和氮气吸附-脱附等手段,对其介孔结构进行了表征.以正丁醛为探针分子,考察了其对有机醛的吸附,并与Y-沸石的吸附性能做了对比.结果表明,材料的介孔比表面积与其对正丁醛的吸附量成正比,吸附等温线符合Langmuir模型,属于单层吸附,具有最大介孔比表面积的MCM-41对正丁醛的吸附量最大(484 mg·g-1).最后将SBA-15添加到卷烟滤嘴中,实验结果表明,SBA-15能显著降低卷烟烟气中巴豆醛的释放量.     

以廉价国产化试剂合成大孔径高度有序介孔氧化硅分子筛

新一代大孔径（１～３０nm）介孔分子筛在大分子转化、吸附、生物大分子分离以及电磁、传感器、光电子等领域均具有广泛的应用前景犤１～４犦。由昂贵的长链有机季铵盐阳离子表面活性剂为模板合成的MCM－４１介孔分子筛，由于其孔径小，水热稳定性差，受到了较大的限制。与其相比，以嵌段高分子共聚物为模板剂合成的介孔分子筛SBA－１５具有孔径均一，有序度高，并且其孔径大以及水热性能良好等优点，近年来得到了广泛的研究犤５～９犦。其骨架上修饰有机硅烷，可用于重金属的分离、回收，以及蛋白质的控释与分离。利用主－客体方法在SB…     

有序介孔碳基金属复合材料的制备及催化应用

有序介孔碳基金属复合材料具有较大的比表面积、规整的孔道结构、良好的热稳定性及化学稳定性、活性金属组分分散度高以及粒径尺寸小等特点,广泛应用于非均相催化领域。常用的合成方法包括浸渍法、“一锅”法以及金属组分转移法等。本文综述了近年来有序介孔碳基金属复合材料的制备及其在非均相催化领域中的应用研究进展,重点阐述了介孔碳载体的介观结构调控、表面性质控制及限域效应等对所负载的活性金属组分的分散性、粒径大小,以及对反应物和产物扩散的影响,探讨了其在气相反应、液相反应和光电催化等领域的应用,并对有序介孔碳基复合材料的发展方向和应用前景进行了展望。     

棒状有序纳米介孔二氧化硅的合成

以十六烷基氯化吡啶为模板剂,甲酰胺为共溶剂,在室温酸性条件下合成了棒状有序纳米介孔二氧化硅,并用扫描电镜(SEM)、小角X射线衍射(SXRD)和N2气体吸附仪对其进行了表征。结果表明,棒状产物形貌规整,形态均一,长度约30～50μm,直径约5μm,具有MCM41的有序六方孔道结构;煅烧后的样品显示典型的Ⅳ型吸附等温线和H1型滞后环,孔径分布很窄,BJH最可几孔径为2.15nm,BET表面积高达1335m2·g-1。     

有序介孔材料在生物医药领域中的应用

本文简述了有序介孔材料的特性,详细介绍了其在生物医药领域中的应用研究,如用于酶的固定化、生物传感器、药物的包埋和控释、生物活性材料、生物分子的吸附和分离等,阐述了不同类型的有序介孔材料在这些应用中的性能以及为适用于该领域应用进行的材料开发和结构修饰,最后对材料的改进和应用前景进行了展望。     

A TEMPO-Functionalized Ordered Mesoporous Polymer as a Highly Active and Reusable Organocatalyst

The properties of high stability, periodic porosity, and tunable nature of ordered mesoporous polymers make these materials ideal catalytic nanoreactors. However, their application in organocatalysis has been rarely explored. We report herein for the first time the incorporation of a versatile organocatalyst, 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO), into the pores of an FDU-type mesoporous polymer via a pore surface engineering strategy. The resulting FDU-15-TEMPO possesses a highly ordered mesoporous organic framework and enhanced stability, and shows excellent catalytic activity in the selective oxidation of alcohols and aerobic oxidative synthesis of 2-substituted benzoxazoles, benzimidazoles and benzothiazoles. Moreover, the catalyst can be easily recovered and reused for up to 7 consecutive cycles.     

Ordered Mesoporous Silica Incorporating Platinum Nanoparticles as Electrode Material for Paracetamol Detection

High ordered mesoporous materials (SBA-15) modified with Al and/or B and Pt nanoparticles (Pt NPs) were used for preparing modified graphite paste electrodes (Pt/M−SBA-15-GPE, where M=Al−, B− or Al−B−) and applied for paracetamol (PA) detection. The electrodes were investigated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Square wave voltammetry (SWV) technique was used to obtain the analytical parameters for PA detection. The acquired values of electrochemical and analytical parameters recommend the mesoporous compound containing Pt NPs to be used as composite electrode material for PA detection in real samples.     

Confined Polymerization in Highly Ordered Mesoporous Organosilicas

Hybrid mesoporous organosilica exhibiting crystal‐like order in the walls provided an ideal channel reaction vessel for the confined polymerization of acrylonitrile (PAN). The resulting high‐molecular‐mass PAN fills the channels at high yield and forms an ordered nanostructure of polymer nanobundles enclosed into the hybrid matrix. The in situ thermal transformation of PAN into rigid polyconjugated and, eventually, into condensed polyaromatic carbon nanofibers, retains the periodic architecture. Simultaneously, the matrix evolves showing the fusion of the p‐phenylene rings and the cleavage of carbon?silicon bonds: this gives rise to graphitic‐carbon/silica nanocomposites containing hyper‐oxydrylated silica nanophases. Interestingly, the 3D hexagonal mesostructure survives in the carbonaceous material. The exploitation of porous materials of high capacity and a hybrid nature, for polymerization in the confined state, followed by high temperature treatments, allowed us to achieve unique and precisely fabricated nanostructures, thus paving the way for the construction of fine‐tuned electronic and light‐harvesting materials.     

Electrochemically Assisted Generation of Highly Ordered Azide‐Functionalized Mesoporous Silica for Oriented Hybrid Films

One key challenge in inorganic mesoporous films is the development of oriented mesostructures with vertical channels, and even more challenging is their functionalization while maintaining accessible the selected surface groups. Combining the electrochemically assisted deposition of ordered and oriented azide‐functionalized mesoporous silica with alkyne–azide click chemistry enables such nanostructured and vertically aligned hybrid films to be obtained with significant amounts of active organic functional groups, as illustrated for ferrocene and pyridine functions. A good level of mesostructural order was obtained, namely up to 40 % of organosilane in the starting sol. The method could be applied to a wide variety of functional groups, thus offering numerous new opportunities for applications in various fields.