软模板合成有序介孔碳材料

有序介孔碳材料由于其较大的表面积、均一的孔径、良好的热稳定性和化学稳定性,广泛应用于吸附、分离、催化以及能量储存等众多领域。与传统的以硅基介孔材料为硬模板的反向复制方法相比,通过嵌段共聚物和聚合物前驱体之间的有机-有机自组装的软模板法简便易行,已成为合成有序介孔碳材料有效方法。本论文综述了介孔碳材料的软模板合成机制、合成方法、功能化及其应用,对合成技术、结构控制、孔径调控以及形貌控制等方面进行了讨论,并探讨了其在吸附、催化、电极材料等领域的应用。     

两亲性嵌段共聚物导向合成有序介孔金属氧化物半导体材料

有序介孔材料作为一种结构稳定、高比表面积、孔径可调、孔壁易于修饰的新型纳米结构材料在基础研究与应用开发方面都引起了人们的关注.有关有序介孔材料的文献中,无定型介孔材料(如二氧化硅、碳材料等)报道占据了大约70%,主要是由于传统软模板剂(如小分子表面活性剂或者聚环氧乙烷-b-聚环氧丙烷基嵌段共聚物)能够胜任无定型介孔材料的合成.相比而言,常规软模板剂在合成具有独特物化性能(光、电、磁以及催化、气敏等特性)的晶态半导体金属氧化物介孔材料方面面临很大的挑战.近年来,随着学科交叉发展以及高分子界研究人员加入无机多孔材料领域,一系列新型嵌段共聚物模板剂(例如具有高残碳率、高玻璃化转变温度和络合能力的嵌段共聚物)相继被合成并用于合成新型多孔材料,特别是这些模板剂在诱导组装合成有序介孔金属氧化物材料方面的研究取得了突出进展.本文从聚合物模板剂的制备与组装出发,围绕金属氧化物前驱体与模板剂之间的相互作用,系统综述了两者组装的作用机理和组装行为.深入探讨并总结了常见的三大组装方式:金属无机盐-聚合物模板、金属簇化合物-聚合物模板、金属纳米晶-聚合物模板组装,详细阐述了聚合物模板在合成有序介孔金属氧化物中的组装机理以及微观结构调控规律,并分析了聚合物模板诱导合成有序介孔金属氧化物未来宏量制备面临的机遇与挑战.鉴于其丰富的物化特性和新颖的介孔结构,有序介孔金属氧化物将逐步成为纳米光电器件、纳米催化载体以及化学传感的核心材料.     

有序介孔碳负载Fe、Co、Ni纳米晶的软模板合成及其表征

报道了在有序介孔碳基体中一步合成负载Fe、Co、Ni纳米晶的方法. 以间二苯酚和甲醛为碳源, F127为模板剂, Fe、Co、Ni的硝酸盐为前驱体, 通过软模板组装路线在酸性条件下合成了负载型有序介孔碳复合材料. 采用X射线衍射(XRD)、透射电镜(TEM)和氮气吸附等手段对所合成材料进行了表征. 结果表明: 合成的材料具有类似于SBA-15的有序介孔结构, 有序介孔碳负载Fe、Co、Ni纳米晶复合材料的比表面积分别为586、626和698 m²·g^-1. XRD和TEM表征结果证实了金属物种以高分散纳米晶的形式分布在介孔碳基体中.     

多阶有序多孔炭的软模板法合成与结构控制

多阶有序多孔炭材料综合了多种多孔炭材料的结构优点,在催化、吸附、储能、电化学等方面具有潜在的重要应用。多阶有序多孔炭材料的合成方法很多,到目前为止,模板法是控制孔结构和调节尺寸的最有效方法。在模板法中,软模板法因为其工艺简单、省时、成本低、环境污染小等优势,近些年来广泛被人们采用。用软模板法合成的多阶有序多孔炭包括:大孔-介孔炭,介孔-微孔炭,介孔-介孔炭,大孔-介孔-微孔炭等。本文对多阶有序多孔炭的软模板法合成与结构控制进行了综述。总结了软模板法在实现上述材料孔结构控制中的影响因素。     

由纳米晶前驱体组装有序介孔silicalite-1分子筛

采用两步法将不同尺寸的silicalite-1分子筛纳米晶种通过自组装合成了一系列有序介孔silicalite-1分子筛。首先将强碱性的silicalite-1前驱体分别加热不同时间得到纳米晶种,然后在类似合成SBA-15的强酸性条件下组装成有序的介孔材料。合成条件的剧烈变化阻止了分子筛晶种的继续长大,并在三嵌段共聚物模板的诱导下组装成有序介孔材料。这种“自下而上”的方法制备有序介孔分子筛同时包含微孔和介孔。氮气吸脱附结果表明所制备的介孔分子筛材料均表现了很大的比表面积(730 m2/g以上)。     

由纳米晶前驱体组装有序介孔silicalite-1分子筛（英文）

采用两步法将不同尺寸的silicalite-1分子筛纳米晶种通过自组装合成了一系列有序介孔silicalite-1分子筛.首先将强碱性的silicalite-1前驱体分别加热不同时间得到纳米晶种,然后在类似合成SBA-15的强酸性条件下组装成有序的介孔材料.合成条件的剧烈变化阻止了分子筛晶种的继续长大,并在三嵌段共聚物模板的诱导下组装成有序介孔材料.这种"自下而上"的方法制备有序介孔分子筛同时包含微孔和介孔.氮气吸脱附结果表明所制备的介孔分子筛材料均表现了很大的比表面积(730 m2/g以上).     

基于模板技术的介孔金属氧化物的生长机理及应用

大比表面积、高孔隙率的介孔金属氧化物具有特殊的光、电、磁、催化等性能,引起密切关注。本文综述了介孔金属氧化物的模板法合成机制及该类材料在催化、电化学、制备新材料等方面的最新研究进展;介绍了软、硬模板法合成机理及产物结晶理论;着重阐述了硬模板法中模板性质、前驱物与介孔孔壁作用力、前驱物的聚集和迁移、实验条件等因素对产物结构的影响;最后,对该类材料的未来发展进行了展望。     

高温水热合成具有高稳定性的有序介孔材料

高温水热合成路线作为合成具有超高稳定性的介孔材料越来越受到人们的重视.本文对高温水热合成有序介孔材料的发展过程作一个简单的综述,合成路线包括使用碳氟表面活性剂和碳氢表面活性剂作为复合模板,有机季铵盐与碳氢表面活性剂作为复合模板以及最近报道的采用碳氢表面活性剂作为单一模板来合成系列的有序介孔材料,其组成为二氧化硅、氧化钛硅以及聚合物等.     

硅藻土辅助制备有序介孔碳及其电催化性能

以共聚物F127 为软模板, 酚醛树脂为碳源, 引入硅藻土充当暂态支架, 在不同硅藻土与酚醛树脂质量比下, 用蒸发自组装法合成有序介孔碳材料. 利用XRD, TEM, N₂ 吸附-脱附对其结构进行表征, 结果显示, 与单一软模板相比,在硅藻土辅助下获得的介孔碳材料不仅具有高度有序的孔道, 还具有更大的比表面积(717～773 m²·g^-1)和孔径(3.9～11.3 nm). 依据原料比例与介孔碳结构两者间的变化规律, 初步探讨了硅藻土在制备中所起的辅助作用. 采用微波多元醇还原法制备介孔碳载Pt 电催化剂, 在甲醇溶液中进行循环伏安测试, 发现比表面积的增大有利于碳材料的电催化性能提高, 当硅藻土与酚醛树脂的比例为0.5 时, 制备出的有序介孔碳比表面积最大, 载Pt 后呈现的正向氧化峰电流也最大.     

双模板法合成介孔/大孔二级孔道碳材料

以酚醛树脂低聚物为前驱物, 利用双模板法制备了具有介孔/大孔双孔结构的碳材料. 其中以二氧化硅蛋白石为大孔模板, 以嵌段共聚物自组装结构为介孔模板. 对样品进行了扫描电子显微镜(SEM), 透射电子显微镜(TEM), X射线衍射(XRD)和氮气吸附-脱附实验表征. 结果表明所制备的双孔碳材料大孔直径约为230 nm, 介孔直径10 nm.     

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.     

Nanocast mesoporous mixed metal oxides for catalytic applications

Since the initial discovery of ordered mesoporous silica in early 1990s, considerable innovations were achieved regarding their synthesis, characterization and applications. One of the best outcomes of these intense research efforts is the development of a solid templating method called “nanocasting”, which is based on using mesoporous silica (or carbon) as a rigid template. This solid-to-solid replication method opened the pathway for synthesizing high surface area non-silica mesostructured materials that are challenging to obtain through conventional self-assembly processes which are based on amphiphilic soft structure-directing agents. In particular, the replicated metal oxide mesostructures obtained by this method were found to be highly versatile for a wide range of applications, especially in catalysis, owing to their large specific surface area. Furthermore, the nanocasting method is particularly suited for the synthesis of mixed metal compositions, favored by the possible confinement of mixed precursors in the nanopores of the template. In this account, we discuss some of the recent developments regarding the synthesis of nanocast mixed metal oxides and their perspectives of catalytic applications. It is here the choice of the authors to place emphasis on a few representative examples of compositions (e.g., non-noble metal-based catalysts, perovskites) and catalytic reactions (e.g., hydrogen production, gas-phase oxidation).     

The characteristics of highly ordered mesoporous carbons as electrode material for electrochemical sensing as compared with carbon nanotubes

In this paper, the unique properties of highly ordered mesoporous carbons modified glassy carbon electrode (OMCs/GE) are illustrated from comparison with carbon nanotubes modified glassy carbon electrode (CNTs/GE) for the electrochemical sensing applications. Electrochemical behaviors of eight kinds of inorganic and organic electroactive compounds were studied at OMCs/GE, which shows more favorable electron transfer kinetics than that at CNTs/GE. Especially, OMCs/GE exhibits remarkably strong and stable electrocatalytic response toward NADH compared with CNTs/GE. The ability of OMCs to promote electron transfer not only provides a new platform for the development of dehydrogenase-based bioelectrochemical devices, but also indicates a potential of OMCs in a wide range of sensing applications. OMCs prepared are the novel carbon electrode materials, exhibiting more favorable electrochemical reactivity than CNTs for the wide electrochemical sensing applications without pretreatments, while purification or end-opening processing was usually required in case of CNTs.     

Efficient synthesis and sulfonation of ordered mesoporous carbon materials

Ordered mesoporous carbons (OMCs) with hexagonal structure were efficiently synthesized via cooperative self-assembly of phenol/formaldehyde resol and surfactant F127 under acidic aqueous conditions. Induced by HCl, a gel phase mainly containing phenol/formaldehyde resol and F127 was obtained within several hours. X-ray diffraction (XRD), transmission electron microscope (TEM) and nitrogen adsorption isotherms indicated that the synthesized samples possess 2-D hexagonal mesostructure. The influence of the synthesis conditions, including acid concentration and mass ratio of resol to F127, was investigated. When the acid concentration was fixed in the range of 0.6-2.0 M and the mass ratio of resol to F127 in the range of 3.5-4.0, highly ordered mesoporous carbon could be synthesized. The synthesized OMCs could be easily sulfonated in concentrated sulfuric acid at elevated temperature. The results indicate that the mesostructural stability and the content of the surface sulfonic acid (SO(3)H) groups depend mainly on the pyrolysis temperature of the OMCs and the sulfonation temperature, suggesting that the combination of pyrolysis and sulfonation temperature is essential for developing OMCs with high densities of SO(3)H groups.     

Influence of Preparation Conditions on Structural Stability of Ordered Mesoporous Carbons Synthesized by Evaporation-induced Triconstituent Co-assembly Method

Various ordered mesoporous carbons (OMCs) have been prepared by evaporation-induced triconstituent co-assembly method. Their mesostructural stability under different carbon content, aging time and acidity were conveniently monitored by X-ray diffraction, transmis-sion electron microscopy, and N₂ sorption isotherms techniques. The results show mesostruc-tural stability of OMCs is enhanced as the carbon content increases from 36% to 46%, further increasing carbon content deteriorates the mesostructural stability. Increasing aging time from 0.5 h to 5.0 h make the mesostructural stability go through an optimum (2.0 h) and gradually reduce framework shrinkage of the OMCs. Highly OMCs can only be obtained in the acidity range of 0.2～1.2 mol/L HCl, when the acidity is near the isoelectric point of silica, the resulting OMCs have the best mesostructure stability. Under the optimum condi-tion, the carbon content of 46%, aging time of 2.0 h, and 0.2 mol/L HCl, the resulting OMCs have the best mesostructure stability and the highest BET surface areas of 2281 m²/g.     

A family of ordered mesoporous carbons derived from mesophase pitch using ordered mesoporous silicas as templates

A variety of ordered mesoporous carbons (OMCs) were synthesized using ordered mesoporous silicas (OMSs) as hard templates and the mesophase pitch (MP) as a carbon precursor. The synthesis included the mixing of OMS with MP, the infiltration of OMS with MP at 450–550?°C and the carbonization of MP in OMS/MP composite followed by the dissolution of the OMS template. OMCs with structures of two-dimensional hexagonal arrays of nanorods and three-dimensional arrays of nanospheres were obtained through the replication of silica templates, including large-pore SBA-15, KIT-6, large-pore FDU-12 and SBA-16. In particular, 2-D hexagonal array of carbon nanorods (CMK-3 carbon) with (100) interplanar spacing of ～13 nm as well as an array of carbon nanospheres arranged in the face-centered cubic structure with the unit-cell parameter of 33 nm were successfully prepared. The specific surface areas of the resulting carbons were up to 400 m²/g, and the total pore volumes were up to 0.43 cm³/g, with the highest values achieved when the MP infiltration temperature was 500?°C. The OMCs exhibited narrow mesopore size distributions. As inferred from XRD, the frameworks of OMCs featured semi-graphitic structures even though moderate carbonization temperature (850?°C) was employed.     

Solution-phase synthesis of ordered mesoporous carbon as resonant-gravimetric sensing material for room-temperature H_2S detection

H_2S can cause multiple diseases and poses a great threat to human health.However,the precise detection of extremely toxic H_2S at room temperature is still a great challenge.Here,a facile solvent evaporation induced aggregating assembly(EIAA) method has been applied for the production of ordered mesoporous carbon(OMCs) in an acidic THF/H_2 O solution with high-molecular-weight poly(ethylene oxide)-b-polystyrene(PEO-b-PS) copolymers as the structure-directing agent,formaldehyde and resorcinol as carbon precursors.Along with the continuous evaporation of THF from the mixed solution,cylindrical micelles are formed in the solution and further assemble into highly ordered mesostructure.The obtained OMCs possesses a two-dimensional(2 D) hexagonal mesostructure with uniform and large pore diameter(～19.2 nm),high surface area(599 m~2/g),and large pore volume(0.92 cm~3/g).When being used as the resonant cantilever gas sensor for room-temperature H_2S detection,the OMCs has delivered not only a superior gas sensing performance with ultrafast re s ponse(14 s) and recovery(21 s) even at low concentration(2 ppm) but also an excellent selectivity toward H_2S among various common interfering gases.Moreover,the limit of detection is better than 0.2 ppm,indicating its potential application in environmental monitoring and health protection.     

Organic acid-assisted soft-templating synthesis of ordered mesoporous carbons

A series of soft-templated ordered mesoporous carbons (OMCs) was synthesized by using resorcinol and formaldehyde as carbon precursors, triblock copolymer Pluronic F127 as a soft-template, and an organic acid (acetic, benzoic, citric, oxalic, or succinic) as a polymerization reaction catalyst. The aforementioned organic acids were strong enough to facilitate the formation of ordered mesophases by the block copolymer template used and to catalyze the polymerization reaction of resorcinol and formaldehyde in this template. The use of weak organic acids instead of strong inorganic acids such as HCl eliminated inorganic anions from the reaction environment and resulted in high surface area OMCs. Basically, the resulting carbons showed the surface areas and pore volumes comparable to those reported for the carbons prepared under similar conditions but in the presence of strong inorganic acids. Electron microscopy analysis proved the presence of ordered mesopores, whereas thermogravimetric analysis showed a good thermal stability of these carbons.     

Aqueous dye adsorption on ordered mesoporous carbons

Ordered mesoporous carbons (OMCs) with varying pore size, and microporous carbon, CFY, were synthesized using ordered mesoporous silica SBA-15 and NaY zeolite as hard templates, respectively. N(2) adsorption tests show that the synthesized OMCs possess abundant mesopores and centralized mesopore distribution. Methylene blue (MB) and neutral red (NR) were used as probe molecules to investigate their adsorption behaviors on OMCs and CFY. As evidenced by adsorption tests, the volume of mesopores of which the pore size is larger than 3.5 nm is a crucial factor for the adsorption capacity and adsorption rate of MB on OMCs. However, the most probable pore diameter of OMCs was found to be vital to the adsorption capacity and adsorption rate of NR. Theoretical studies show that the adsorption kinetics of MB and NR on OMCs can be well depicted by using pseudo-second-order kinetic model.     

Facile synthesis of ordered mesoporous carbons with high thermal stability by self-assembly of resorcinol-formaldehyde and block copolymers under highly acidic conditions

The effect of phenols reactivity with formaldehyde on the formation of ordered mesoporous carbons has been investigated. A strategy to accelerate the polymerization of phenolic resins by using strongly acidic conditions is proposed. The self-assembly of resorcinol-formaldehyde and block copolymers (e.g., F127) under highly acidic concentrations (e.g., 1.5 M HCl) is probably driven by the I+X-S+ mechanism and hydrogen bonding and affords a highly reproducible approach for synthesis of ordered mesoporous carbons. The synthesis can be readily scaled up with no change in sample quality. The carbon material obtained (denoted as C-ORNL-1) exhibits highly ordered hexagonal mesostructure, with a typical BET surface area of approximately 600 m2/g, pore size of 6.3 nm, and pore volume of approximately 0.60 cm3/g. One of the unique structural features of C-ORNL-1 is its high thermal stability; it can be graphitized at 2600 degrees C while considerable mesoporosity is maintained.