介孔材料结构和孔道的可控合成及其在电化学和生物分离中的应用

【作者】 陈德宏；

【导师】 赵东元；

【作者基本信息】 复旦大学 ， 无机化学， 2006， 博士

【摘要】 介孔分子筛是指孔径介于2-50 nm之间的一类无机多孔材料，它的孔道结构高度有序，具有很高的比表面积，在多相催化、吸附、分离、传感器等众多领域有广泛的应用前景。自从1992年Mobil公司的研究人员首次报道了M41S系列的介孔材料以来，它就一直受到人们的广泛关注。目前，越来越多的研究者以超分子模板法合成出了具有不同组成，新型孔道结构以及具有特殊性质的介孔材料。但是要在各种尺度上对介孔材料进行控制合成，并揭示材料结构与性质间的关系仍然是未来各国科学家们急待解决的问题，因为只有掌握了对介孔材料的可控合成方法，才能从材料设计的角度获得需要的功能性介孔材料，并最终将其运用到更多领域，实现商业化的应用。由此可见，在微观、介观和宏观尺度上对介孔材料进行控制合成，并探索介孔材料新的应用将成为这个领域未来的研究重点。本论文分为两大部分：第一部分使用阴／非离子混合表面活性剂作结构导向剂来控制合成具有不同介观结构的二氧化硅分子筛材料；第二部分利用聚合诱导胶体聚集的方法制备得到了具有石墨化微晶结构且骨架含氮的大孔径介孔碳微球材料和晶化的氧化铁微球材料，并分别考察了它们在高功率双电层电容器及在磷酸化肽富集分离中的应用。先前以超分子模板法合成有序介孔材料的过程主要涉及到两类表面活性剂：分别是以合成M41S系列介孔材料为代表的阳离子表面活性剂和以制备SBA-n系列介孔材料为代表的嵌段聚合物型非离子表面活性剂。但是，由于阳离子表面活性剂不易合成，其价格高，这就使得用这类表面活性剂所合成的介孔材料成本较高，不利于该类材料的推广使用。当前，在工业上大量生产和使用的表面活性剂中，阴、非离子两类表面活性剂合成技术完善，生产成本较低，并且它们在很多情况下可以复配使用，以提高其表面活性。如果能用它们作为结构导性剂来合成介孔材料，可以降低材料的生产成本，推进介孔材料的实用化。为解决这一问题，同时保证能得到高度有序的介孔材料，在第二章中，我们利用国产阴离子表面活性剂十二烷基硫酸钠(SDS)或十二烷基苯磺酸钠(SDBS)与非离子表面活性剂(P123)进行复配，利用其独特的胶束行为，组装得到了具有立方双连续结构(Ia(?)d)的大孔径二氧化硅分子筛材料。该材料具有高的比表面积(770 m~2／g)，大的孔容(～1.5 cm~3／g)和孔径(～10 nm)，同时，该材料在950℃高温下处理后，仍能保持其高度有序的介观结构，说明它具有高的热稳定性。在合成体系中加入无机盐，可以实现对所得材料宏观形貌的控制，制得了珊瑚状和花瓣状的介孔材料。我们考察了影响立方双连续结构二氧化硅形成的各种因素，最终给出了合成该材料的最佳实验条件。在第二章工作的基础上，我们选用具有特殊分子结构的阴离子表面活性剂二-(2-乙基己基)琥珀酸酯磺酸钠(AOT)与非离子表面活性剂F127进行复配。通过调变AOT和TMB的加入量，在一个相对简单的F127-AOT-TMB体系里，实现了对大孔径二氧化硅分子筛介观结构(面心立方Fm(?)m→体心立方Im(?)m→二维六方p6m→立方双连续Ia(?)d)的连续调变。制得的介孔材料具有大面积的有序性、高的比表面积、大的孔容及均一的孔径分布。相比于一般合成介孔分子筛的方法，我们所报道的合成体系显示出了很好的结构可控性，这为大批量制备具有不同介观结构的二氧化硅分子筛材料提供了一个简单实用的合成方法。超分子模板组装是一种非常有效的合成介观结构的的方法。但是如果无机骨架的溶胶—凝胶过程难以控制，这种方法往往难以奏效。第四和第五章中，我们利用聚合诱导自组装方法制得了具有较大晶间孔的非硅介孔材料，并考察了所得材料在电化学和生物分离中的潜在应用。第四章中，我们利用廉价易得的三聚氰胺甲醛树脂为前躯体，经过高温炭化处理制得了骨架含氮的介孔碳微球材料。该类材料同时具有高比表面积(～1460 m~2／g)、大孔径(～30 nm)、大孔容(～5.4 cm~3/g)适量的含氮基团及部分石墨化的纳米碳结构，这些性质有利于电荷在其表面的存贮、水合离子在其孔道中的快速迁移扩散、增强电解质溶液对其表面的润湿性以及提高材料导电性的作用。循环伏安和恒流充放电测试表明，该材料能够在很宽的电流密度区间(1～50 A／g)内保持住很好的双电层电容性能。作为双电层电容器的电极材料，它具有比一般商业化活性炭材料更高的质量比容量和大电流充放电性能。此外，该制备过程简单，周期短，充分利用了现已商品化的廉价化学原料，适合该类材料的批量制备。第五章中我们介绍了一种大孔径氧化铁微球材料的合成及其在磷酸化肽段富集分离中的应用。大孔径氧化铁微球材料的合成是利用尿醛树脂的缩聚来诱导氢氧化铁溶胶粒子间的聚集，并在空气中热处理后得到的。所得材料的粒径为～3μm，孔径为48 nm。为了探索其潜在应用，我们将大孔径氧化铁微球材料用于磷酸化肽段的富集分离，发现了其比以往所报道材料更为优秀的富集能力，具体表现为它对复杂蛋白酶解肽液中的单位点和多位点磷酸化肽段能够高选择性地实现富集分离，而且对于商品化casein蛋白酶解肽液中的磷酸化肽段能够达到高效率地富集作用，富集覆盖率占到了该蛋白理论磷酸化位点总数的93％。同时，使用介孔氧化铁材料来富集分离磷酸化肽段还可以明显地简化分析步骤。考虑到该材料的制备过程简单，所需原料容易获得，所得氧化铁材料廉价、无毒等特性，这种大孔径氧化铁微球材料有望在生物大分子富集分离领域中得到很好的应用。更多还原

【Abstract】 As a kind of porous inorganic materials with the pore size between 2-50 nm, mesoporous molecular sieves might find a lot of applications in the fields of catalysis, adsorption, sensor and so on, because of their highly ordered pore structures and very large specific surface areas. Since the first report about M41S mesoporous materials by the scientists at Mobil Research and Development Corporation, researchers around the world have prepared thousands of mesoporous materials with different compositions, new pore systems and novel properties based on supermolecule assembly concept. However, rationally controlling the mesoporous materials at micro-, meso- and macro-scale and giving some ideas of structure-property-function relationships is still a urgent challenge for the scientists all over the world in this field. When above-mentioned problem can be really solved and the design of goal-materials based on their application can also be realized, the promising commercial utility of mesoporous materials is expected to come into being finally. Thus, to exploit the controlling methods for mesoporous materials on micro-, meso- and macro-scale would be the main task in this field in the future.This thesis divides into two major parts: in the first part, the control on the mesostructures of silica materials templated by using anionic-nonionic mixed surfactants is described. Nitrogen-containing carbon microspheres with very large pore size and iron oxide microspheres with well-crystallized structures have been prepared by using a facile polymerization-induced colloids aggregation method in the second part, and their potential applications in the fields of high-power electrical double layer capacitor （EDLC） and selective enrichment of phosphopeptides are respectively characterization.Two kinds of surfactants including cationic ones and nonionic block copolymers are mainly used for the preparation of mesoporous materials in previous reports, which are respectively represented by the synthesis of M41S or SBA-n series materials. However,the cationic surfactants are usually expensive, which will hamper the practical application of resulting mesoporous materials because of their relatively higher costs. In view of the facts that both anionic and nonionic surfactants are very cheap and have been widely used in industrial fields in the processing of their various formulations, research on the synthesis of mesoporous materials templated by anionic-nonionic mixed surfactants may not only be theoretically important, but also provide more options for economical and large-scale productions of mesoporous materials with controllable structures.In chapter 2, mesoporous silica with Iα （?）d structure has been successfully prepared by using mixed surfactants of commercially available nonionic block copolymer P123 (EO₂₀PO₇₀EO₂₀) and anionic sodium dodecyl sulfate （SDS） or sodium dodecyl benzene sulfonate （SDBS） as structure-directing agents through an acid-catalyzed silica sol-gel process. The products have highly ordered bicontinuous cubic mesostructure with large surface area （～ 770 m²/g）, pore volume （～ 1.5 cm³/g） and uniform pore size （～ 10 nm）. The results based on the 950 ℃ high temperature treatment indicate that resultant template-free mesoporous silica products have excellently thermal stability. Morphologies of the resultant materials can further be controlled by adding inorganic salt （such as Na₂SO₄） into the mixed surfactants system and coral- and petaline-like mesoporous silicas with continuous skeletons have been prepared. Effects of preparation parameters on the formation of the mesostructure have been extensively investigated and optimum conditions for resulting mesoporous materials are given.Based on the work of chapter 2, another special sodium dioctyl sulfosuccinate （AOT） anionic surfactant has been chosen to mix with nonionic F127 block copolymers for the preparation of mesoporous materials. A successive mesophase transformation induced by AOT molecules has been demonstrated to fabricate four kinds of large pore mesoporous silica materials in a triblock copolymer F127 surfactant assembly system. The transformation of the highly ordered mesostructures from face-centered cubic （spacegroup Fm（3）m） to body-centered Im（?）m then towards two-deminsional （2-D） hexagonalp6m and eventual to cubic bicontinuous Ia （?）d symmetries has been achieved by tuningthe amount of AOT and 1,3,5-trimethylbenzene （TMB）. These mesoporous silica structures have highly ordered regularity in large domains and possess high surface areas, large pore volumes and uniform pore sizes. The understanding of blend-surfactant assemble mechanism will lead to a more rational approach for economical and large-scale production of mesoporous materials with controllable structures.Supermolecule assembly methodology is valuable to prepare mesoporous materials. However, this process encounters limitations when the sol-gel process of some inorganic components could not be efficiently controlled. In chapter 4 and 5, a polymerization-induced colloids aggregation method has been used to synthesis nitrogen-containing carbon microspheres with very large pore size and iron oxide microspheres with well-crystallized structures, and their potential applications in the fields of high-power electrical double layer capacitor and selective enrichment of phosphopeptides are respectively characterization.In chapter 4, a kind of graphitized mesoporous carbon spheres （MCS） materials containing in-frame incorporated nitrogen have been successfully prepared by using low-cost melamine-formaldehyde resin （MF） as the precursor. The as-prepared MCS materials simultaneously possess the following characteristics: high specific surface areas （1460 m²/g） for charge storage, large pore size （31.0 nm） to facilitate the ion diffusion with a high speed, suitable quantity of nitrogen （6.34 wt%） on the surface of the materials to enhance its wettability by the electrolyte and fairly good graphitized carbon nanostructures to reduce the electrode resistance. The electrochemical performances based on the cyclic voltammetry （CV） analysis and galvanostatic charge/discharge measurements indicate that as-prepared MCS materials present much better specific capacitance and rate capability as the electrode for EDLC than the most popularly applied activated carbon when constantly charged/discharged over a wide loading current range （1-50 A/g）. In addition, the precursors used in this simple process are commerciallyavailable low cost chemicals, which will be favourable in the preparation of MCS on a large scale.A facile polymerization-induced colloids aggregation method has been used to synthesis iron oxide microspheres with well-crystallized structures in chapter 5, and their potential application in the field of selective enrichment of phosphopeptides from complex sample are also conducted by using MALDI-TOF-MS method. The resulting iron oxide materials are monodisperse microspheres with the diameter ca. 3 μm, and their pore sizes are as large as 48 nm. The results based on the MALDI-TOF-MS analysis suggest that resulting iron oxide microspheres has a high selectivity to enrich both mono-and multi-phosphopeptides from tryptic digest of complex proteins, and the coverage of phosphopeptides for tryptic digest of commercial casein proteins amounts to 93%, indicating a better selective enrichment ability than previous reported materials. In addition, the process of concentrating phosphopeptides is hugely simplified by using mesoporous iron oxide spheres as compared with the well-known IMAC method. In consideration of the preparation process for mesoporous iron oxide microspheres is very simple and low-cost, the resulting mesoporous iron oxide spheres are expected to have potential application in the isolation of phosphopeptides prior to MS analysis.更多还原