【作者】 孔爱国；

【导师】 单永奎；

【作者基本信息】 华东师范大学 ， 分析化学， 2008， 博士

【摘要】 有序多孔材料具有大量纳米孔道,结构空旷,表面积巨大,在光、电、磁、催化、生物医药、传感和纳米工程等方面都有巨大潜在应用价值,已成为一个新兴的蓬勃发展的跨学科研究领域。经过15多年的研究,一大批孔径可调,组成可变、形貌多样、孔道形状不一,且孔道排列方式多样化的新型介孔材料被不断的合成出来。从起初的纯二氧化硅介孔分子筛到各种非硅骨架的介孔材料,从无机介孔骨架到无机.有机介孔骨架,再到纯有机骨架的介孔材料;从具有单一功能的介孔材料,到具有各种复合功能的介孔材料;从有机模板自组装合成法到无机模板浇铸法,另外到已开始出现的无机-有机混合模板法等,人们已经取得了很多突出的成绩。然而,介孔材料的研究中仍然存在许多未知和不足需要我们探索和寻求解决之法。开发简单、快速、经济、普适、易重复、能大规模生产高质量介孔材料的新方法,探索介孔材料本身的新功能,并不断推进介孔材料在各领域中的新应用,逐步实现介孔材料的实用化仍有大量的工作需要我们去做。这个征途中充满了众多挑战和机遇。有序介孔金属氧化物是目前广受关注的一大类新型介孔材料。相对于二氧化硅材料,过渡金属氧化物常常是半导体材料,骨架组成中多存在多种变价的金属元素,许多金属氧化物本身既是很好的催化或光、电、磁等方面的优异材料。合成大比面积,具有有序纳米孔道的介孔过渡金属氧化物材料可为介孔材料开辟新的应用领域,已经展示出硅基介孔材料所不能及的应用前景。然而,金属氧化物的溶胶-凝胶过程难以控制,而且不同金属氧化物,其溶胶-凝胶过程千差万别。采用合成介孔二氧化硅的策略来制备介孔金属氧化物,常常得到的是具有较低结晶度的孔壁,热稳定性和水热稳定性较差的介孔金属氧化物。利用硬模板法可以成功获得多种介孔金属氧化物,然而现有的前驱物填充过程常常较为复杂或者使用大量有机溶剂,而且主要依靠模板的毛细管作用力,不能很好控制前驱物的填充方向,存在填充有效性较低等问题。开发合成介孔材料的新方法,解决其合成中存在的诸多问题,制备具有新颖特点的介孔金属氧化物或复合物材料,并探讨其相关功能性质仍然是介孔材料研究中的主题之一。针对硬模板法合成中填充过程复杂,填充有效性低和前驱物难以控制等问题,我们开发了一种新颖的一次真空纳米浇铸新方法。在前驱物进入介孔模板前,通过人工造成的模板孔内外的超高压力,从而实现定向推动大量前驱物进入介孔孔道,实现模板孔道的一次有效填充。通过这种方法,我们已经合成了一系列具有较高比表面和具有狭窄孔径分布的介孔过渡金属氧化物,并将该方法成功拓展到稀土氧化物材料合成领域,获得了一系列含少量硅的介孔稀土氧化物材料。铜硅复合介孔材料是一种非常有效的氧化还原催化剂,常通过直接合成方法或后处理方法获得。目前,直接合成方法存在氧化铜含量低,特别是酸性条件下,高氧化铜的直接负载一直是个难题,而后处理方法获得的负载铜物种很难控制等。基于此,利用嵌段共聚物在无机盐体系中特殊原位氧化作用,我们开发了一种直接合成具有高氧化铜含量的介孔二氧化硅的新方法,解决了在酸性条件下氧化铜负载量低的问题。直接得到了37.5wt%氧化铜负载的六方介孔SBA-15分子筛;通过调节此体系的无机盐含量,也能直接得到含有45.3wt%氧化铜的立方KIT-6介孔材料。相对于浸渍合成的材料,这些材料在苯羟基化反应中表现出更好的催化性能。另外,在无机盐-水体系中后处理嵌段共聚物杂化的介孔SBA-15材料,我们在介孔孔道内首次获得了草酸铜配合物纳米线物质。通过简单焙烧,大面积的CuO和Cu₂O纳米线可在介孔二氧化硅孔道内生成。这种方法适用于几乎所有嵌段共聚物的原位氧化,可以获得多种铜物种修饰的复合材料,甚至能够被用来完全去处介孔酚醛树脂高分子材料中的模板,首次在介孔高分子孔道内实现了草酸铜配合物和金属铜的定向组装,获得了多种新颖材料。目前介孔γ-Fe₂O₃材料报到较少,获得的材料比表面积较低。我们以硬模板复制介孔CMK-3的方法,通过两次纳米浇铸,得到了具有一定有序介孔结构的超顺磁性γ-Fe₂O₃材料。由于介孔CMK-3提供的原位还原作用和碱催化低温去除模板的方法,有效避免了介观骨架的塌陷,使这种材料具有相对较高的比表面积（187m²/g）。我们以廉价环保的工业级烷基糖苷为结构导向剂,在水溶液中获得了一种具有蠕虫状结构的介孔二氧化硅材料。合成方法简单,原料便宜,表面活性剂具有环境友好特性。而且烷基糖苷表面活性剂具有较高含碳量,通过原位碳化,可以得到一种具有良好吸附性能的介孔碳材料。运用“酸碱对理论”,我们通过在二氧化钛挥发诱发自组装过程中加入少量Ce元素,优化合成条件后,可以快速得到一种具有晶化孔壁的介孔二氧化钛材料。其在甲基苯乙烯光氧化制备苯乙酮过程中显示出优良的催化性能。更多还原

【Abstract】 Ordered mesoporous materials with high surface and numerous nanoscale pore channels are attracting much attention because of their unique applications in catalysis, optics,electrics,magnetism,nanotechnology,and sensors et al.Many efforts have been devoted to study the synthesis and applications of these materials since 1992.A great numbers of mesoporous materials with the different composition,structure,pore size and morphology have been obtained through the different methods.The composition of pore-walls changed from silica to different metal oxide,metal sulfide, and further many mesostuctures with pure organic or inorganic-organic framework. The mesoporous composite materials with several functional actions are attracting the increasing attention.Varsities of synthetic techniques,i.e.Sol-Gel,Hydrothermal, Ultrasonic,Nanocasting,Coating,Grafting et al,have been used to prepare ordered mesoporous materials by soft-template or hard template route.However,many challenges and difficulty need to be overcame in the large-scale production and application of ordered mesoporous materials.The general synthetic methods with simple,fast,inexpensive and environmental-friendly properties must be developed to obtain the ordered mesoporous materials with high quality,i.e high thermal and hydrothermal stability.The new potential function of the different mesoporous materials should be study in detail for their more widely application in new fields.Ordered mesoporous metal oxides with high surface have already attracted much attention because of their numerous potential applications.In contrast to mesoporous silica materials,metal oxides mesostructure often show their special properties such as the different composition,structure,and these metal oxides reveal a large amount of potential applications in catalysis,optics,electrics,magnetism et al.Wide efforts have been made over the past decade to develop new methods for the preparation of these mesoporous materials.However,owing to their complexity of reactive properties and chemical stability intrinsic in the desired constituents,as well as the difficult control of hydrolysis,polymerization,cross-linkage,and inorganic-organic assembly,most oxides are disordered or hybrid-mesostructured by soft-template route, that is,more distinct for multicomponent mesoporous solids.It is not general although several methods have been applied into controlling the hydrolysis of inorganic precursors,for example,relying on metal chlorides and coordination.Recently,the nanocasting technique using mesoporous silica and carbon as hard template represents the other important opportunity for synthesis of ordered nonsiliceous mesoporous metal oxides materials.The most fascinating success is the replication of mesoporous carbon materials.Unfortunatly,other inorganic replicas are not as successful that normally consist of disordered nanowires or nanoparticles without long-range periodicity owing to the partial loadings of precursors inside the mesopores and the fast growth of guest molecules outside the mesopores.How to promote the filling of guest into the hard host is therefore an urgent task,especially for metal oxide precursors.In general,it is still a focus to develop the effective synthetic methods for mesoporous metal oxides with novel properties.Here we developed a novel and generalized one-step wetness impregnation nanocasting pathway that can drive concentrated inorgnic precusors into the channels of hard template in one time.A series of ordered cubic mesoporous rare earth oxides with high surface and amorphous structure have been firstly prepared,and this method can also be successfully extended to obtain ordered crystalline mesoporous metal oxides with high surface such as Co₃o₄,Cr₂O₃,NiO et al..Unlike the traditional nanocasting process,we attempt to produce the high negative pressure in the internal-pores of hard template,which not only results in the more available space of host template and but also provides guest precursors incorporation with a powerful directional,transportation force from the large difference of pressure between internal-pores and external-pores.In the second section,a novel general route has been developed to introduce high copper species into the block copolymer templated mesoporous materials such as silica or polymer.The general key is that a large amount of copper oxalate can be in-situ produced by the oxidation of block copolymer in a special solution containing copper ions.Based on it,the one-step direct method has been applied to obtain CuO loaded（～37.5wt%）large-pore mesoporous SBA-15 with well-dispersed properties in ethanol-water solution.Cubic mesoporous silica with even higher CuO loading （-45.3wt%）also was directly prepared by the simple adjustment of copper precursor amount in the same system.Two kinds of CuO modified mesoporous silica show the enhanced catalytic properties,in comparison to mesoporous CuO/silica obtained by the traditional impregnation method.Besides,we successfully obtain copper oxalate nanowires inside the nanoscale channels of mesoporous silica when the hybrid mesoporous silica composites obtained was treated in this special solution.Especially, as we known,it is the first 1D organic coordination compound nanowires inside the mesoporous channels.Furthermore,we have testified that large-scale and high intensity copper oxide nanowires embedded in the mesoproous channels can be also easily given by calcinations of mesoporous CuC₂O₄/SBA-15 composites.This special method easily overcomes the remarkable difficulty to introduce two absolutely different species of organicmetallic salt into the mesoporous channels.It can also be widely applied to create copper species nanostructures inside block polymer-templated mesoporous channels and obtain useful copper species-modified mesoporous functional materials.Mesoporousγ-Fe₂O₃ with nanocrystalline walls and high surface area has already been synthesized using mesoporous CMK-3 carbon as hard template.TEM images show the worm-like mesostructure of as-prepared sample. Brunauer-Emmett-Teller analysis shows that it has high surface area(187m²g^-1)and large mesopore size（5.0nm）.To the best of our knowledge,so far it is superparamagnetic mesoporousγ-Fe₂O₃ samples with the highest surface area,which maybe enhances its properties such as magnetic storage,catalysts,and potential electrodes et al.At the same time,Magnetic properties of iron oxide have also been characterized by Mo"ssbauer spectra and magnetization curve measurements.We developed a new low-cost synthetic procedure to obtain worm-like mesoporous silica using environmental friendly and industrial grade cation alkyl polyglycoside as structure-directing agents.What is more,mesoporous carbon materials can be obtained through the direct pyrolysis in N₂ of silica/ cation alkyl polyglycoside composites with trace mount H₂SO₄ as catalyst,which is the first sample prepared by the direct pyrolysis of structure-directing agents in worm-like mesoporous silica channels.Furthermore,mesoporous carbon synthesized shows more effective absorption performance for fuchsine dyes in aqueous solution than commercial active carbon.In the final section,with a short synthetic period,highly ordered mesoporous titania with crystalline anatase walls has been synthesized through modified sol-gel method in a nonaqueous solution.Trace mount Ce³⁺addition did not affect the synthetic period,and remarkably enhanced the thermal stability of mesoporous titania resulting in the formation of mesoporous titania with crystalline framework. Crystalline mesoporous titania exhibits excellent properties in photo oxidation ofα-methystyreme to acetophenone.更多还原