Polyethyleneimine-loaded bimodal porous silica as low-cost and high-capacity sorbent for CO2 capture

In this work, bimodal (meso-macro) porous silicas with different mesopore diameters synthesized by using rice husk ash as a low-cost silica source and chitosan as a natural template were used as a polyethyleneimine (PEI) support for CO₂ capture. Unimodal porous silica supports with equivalent mesopore diameters to bimodal porous silica supports have been prepared for purpose of comparison. Effects of different PEI contents (10, 20, 30, 40 and 50 wt%) on CO₂ sorption capacity have been systematically investigated. The porous silica supports and the PEI-loaded porous silica supports were characterized by N₂-sorption analysis, scanning electron microscopy, Fourier transform infrared spectroscopy and thermal gravimetric analysis. CO₂ sorption measurements of all PEI-loaded porous silica supports were performed at different adsorption temperatures (60, 75, 85, 90, 95 and 105 °C). At low PEI contents (10–20 wt%), the CO₂ sorption of all adsorbents was found to decrease as a function of adsorption temperature, which was a characteristic of a thermodynamically-controlled regime. A transition from the thermodynamically-controlled regime to a kinetically-controlled regime was found when the PEI content was increased up to 30 wt% for PEI-loaded unimodal porous silicas and 40 wt% for PEI-loaded bimodal porous silicas. At high PEI contents (40–50 wt%), the CO₂ capturing efficiency of the PEI-loaded bimodal porous silicas was found to be considerably greater than that of the PEI-loaded unimodal porous silicas, indicating that most of the amine groups of PEI molecules loaded on the unimodal porous silica supports was useless, and thus the appeared macroporosity of the bimodal porous silica supports could provide a higher effective amine density to adsorb CO₂.     

Titania nanotube/hollow sphere hybrid material: Dual-template synthesis and photocatalytic property

Inspired by the complicated structure of natural substances, we designed and fabricated nanotube/hollow sphere hybrid structured functional anatase titania material. Cellulosic substance (commercial filter paper) was chosen as nanotube template while silica and polystyrene colloidal microspheres with different diameters were employed as hollow sphere templates. The ultrathin nature of titania layer enabled faithful replication of the nanoscopic structural details of both the template substances. The microsphere and cellulose templates were removed by calcination for polystyrene microsphere template case, and further alkali treatment was carried out to dissolve away the silica component for silica microsphere template case. The obtained anatase titania nanotubes were decorated with nanoscale titania hollow spheres with wall thickness of about 7.5 nm. The resulted hybrid materials exhibited similar but superior photocatalytic efficiency compared with simple titania nanotube structured materials due to the higher surface area endowed by the complex highly porous structure.     

结构有序、双重孔隙中孔炭材料的合成与表征

采用纳米涂层技术,以介孔分子筛SBA 15为模板,在其纳米孔道内引入糠醇/草酸溶液,经原位聚合,炭化后制得炭/SBA 15复合物。采用化学法脱除模板后制得具有规则结构的中孔炭。高分辨TEM表征结果显示该中孔炭是由纳米炭管相互联接、堆积而成,且具有六方对称结构。氮吸附结果显示其比表面积高达2000m2/g,孔径呈双峰分布。孔径相对较大的孔隙来源于SBA 15孔道经纳米涂层后所保留的孔隙;孔径相对较小的孔隙来源于SiO2移除后遗留的纳米孔空间。该方法可应用于以其他多孔氧化硅为模板制备新型纳米复合物的研究过程。     

A simple method of preparing ordered and three-dimensionally-interconnected macroporous carbon with mesoporosity by using silica template

A simple and cost-effective method for the production of porous macro–meso structures is proposed. The approach involves using of monodispersed silica particles and in situ polymerized silica network as a removable template, and using resorcinol-sucrose derivative polymer as a carbon source. The three steps – carbon precursor, silica particles, template – are synthesized simultaneously through sol–gel reaction in one-pot system. The sample prepared by this method was characterized by scanning electron microscopy (SEM) and nitrogen adsorption and desorption, and the results present us a well long-ranged ordered structure and three-dimensionally interconnected macroporous carbon with mesoporosity.     

Pore structure control of mesoporous carbon as supercapacitor material

The pore structure and electrochemical performances of mesoporous carbons prepared by silica sol template method as electrode material for supercapacitor were investigated in this work. The pore size distribution of the mesoporous carbons changes from unimodal to bimodal and the mean pore size increases with the increase of silica sol/glucose ratio. The specific capacitance of the mesoporous carbons also increases with the increase of silica sol/glucose ratio. A novel technique named as template–chemical activation method, combining both template and chemical activation methods, is proposed, which can effectively control the pore structure, improving the electrochemical properties of the mesoporous carbon with improved porosity especially microporosity.     

Wet powder processing of sol-gel derived mesoporous silica-hydroxyapatite hybrid powders

This paper describes a method by which a porous silica coating layer can be obtained on different apatite particles through a simple sol-gel synthesis route. Sol-gel derived powders of hydroxyapatite (HAP) and beta tricalciumphosphate (beta-TCP) were coated with a mesoporous silica using C16TAB (hexadecyltrimethylammonium bromide) as a template in order to induce mesophase formation. Further calcination of the material removes the template from the mesophase and leaves a highly ordered hexagonal arranged mesoporous silica structure with a core of HAP/beta-TCP. The phase purity of the SiO2/apatite composites has been thoroughly investigated by the means of FT-IR, XRD, and solid state 31P MAS NMR. The phase purity of these materials is shown to be dependent on the solubility properties of the used apatites. The hybrid materials are suitable as a multifunctional biomaterial where osteoconductive properties can be combined with drug delivery.     

蓝光波段左手材料的化学制备方法

采用双模板辅助化学电沉积法,以聚苯乙烯微球为初级模板,二维ZnO有序多孔薄膜为二级模板,制备了银树枝状结构阵列,研究了沉积电压对ZnO有序多孔薄膜质量和银树枝形貌的影响,实现了蓝光波段的左手效应.可见光透射和平板聚焦实验表明,当沉积电压为0.5V、聚乙二醇-20000浓度为3mmol/L、沉积时间为8min时,所制备的银树枝状结构阵列具有规则的分形结构,可以在蓝光波段480nm处实现左手效应.     

Synthesis and characterization of ordered mesoporous silica by using polystyrene microemulsion as templates

A simple room temperature synthesis of pure mesoporous silica by using a homemade and functional template: polystyrene microemulsion is reported. The process consists of HCl-catalysed sol-gel reactions of tetraethyl orthosilicate (TEOS) in polystyrene microemulsion, followed by removal of the template via solvent extraction or calcining. X-ray diffraction, Transmission Electron Microscope and N₂ adsorption-desorption isotherms are then used to characterize the mesostructure. The results indicate that the synthesized mesoporous silica has a large BET surface area with more than 900 m²/g, large pore volume with more than 0.8 cm³/g and ordered mesopore-structure. This provides a possible way to control the meso-structure and pore size of mesoporous materials via potential functional templates.     

Synthesis of submicrometer-sized hollow titania spheres with controllable shells

Submicrometer-sized hollow titania spheres with controllable shells have been prepared using polystyrene particles as a template in conjunction with the sol–gel method. The hollow spherical structures could be confirmed by transmission electron microscope (TEM) and scanning electron microscope (SEM). The void sizes of the hollow spheres were 15–20% smaller than the diameters of the polystyrene template. The shell thickness and surface roughness of the hollow titania spheres increased with increasing the concentrations of titanium tetrabutoxide ethanol solutions. Furthermore, when the volume ratio of titanium tetrabutoxide to ethanol was 1:5, a porous titania structure was yielded, rather than dispersive hollow titania spheres. As expected, the shell thickness of the hollow titania spheres could be readily controlled by altering the number of the titanium tetrabutoxide layers coated on the polystyrene template.     

鼠李糖脂碳吸附剂的制备及其吸附性能的研究

以蔗糖和硅酸钠分别作为碳、硅凝胶的前驱体, 经溶胶-凝胶反应形成硅凝胶和蔗糖聚合物的混合网络结构, 高温炭化后将二氧化硅刻蚀去除, 制备了一种以中孔径为主的多孔碳材料, 其孔径可以通过反应条件的改变控制在8~25nm范围内, 经过扫描电子显微镜的观察以及低温氮气吸附等温线分析发现, 在蔗糖/硅摩尔比为0.33、溶胶pH值为3、凝胶温度为80℃、炭化温度为850℃时, 所制得的中孔碳BET表面积为597.63 m²/g、孔容及中孔率好, 对鼠李糖脂有良好的吸附性.     

Synthesis of new silicas with high stable and large mesopores and macropores for biocatalysis applications

Monomodal or bimodal porous silicas with large mesopores, constituted by particles or having a monolithic (block type) morphology, respectively, are synthesized using sodium silicate as siliceous species source, cetyltrimethylammonium bromide (CTAB) as pore template and ethyl acetate (EtAc) as pH modifier. The monomodal porosity is represented by 20–30 nm pores and the bimodal one by these pores and also macropores. These characteristics are modulated in function of the CTAB and EtAc concentrations as well as the pH and hydrothermal treatment. The role of these reagents upon the porosity is rationalized. The presence of high CTAB concentration and a rather low pH decreasing rate (function of EtAc concentration and hydrothermal treatment) are essential for having the already known bimodal mesoporous silicas (BMS). On the contrary a rather high pH decreasing rate promotes the formation of the new bimodal mesoporous–macroporous silicas (BMMS) synthesized in this work, where the EtAc also plays the role of emulsion forming agent. The hydrolytic stability of the synthesized silica under aqueous conditions, at different pH values, makes these silicas good candidates for application in different areas of catalysis, especially in the enzymatic one.     

《二氧化硅孔材料的模板合成》化学综合实验的建设

化学综合实验"二氧化硅孔材料的模板合成"是为大学化学专业本科生开设的一个实验教学课程。其实验的主要内容是,首先合成制备单分散的聚苯乙烯乳胶粒子,然后以此单分散的聚苯乙烯乳胶粒子为初始材料,利用胶体晶模板法制备二氧化硅三维有序孔材料。利用透射电子显微镜和扫描电子显微镜对所制备的各级样品进行表征。教学实践发现,当作为初始材料的聚苯乙烯乳胶粒子尺寸较大时,三维有序孔材料的制备成功率高。文中介绍了此实验的建立以及对其进行改进的过程。     

大面积3D有序介孔二氧化钛薄膜光子晶体制备与性能研究

介绍了大面积有序反蛋白石结构介孔二氧化钛薄膜光子晶体制备与性能研究的进展.为了保证二氧化钛骨架结构的稳定性和有序度,从而使氧化钛介孔薄膜达到大面积结构均匀,在介孔薄膜制备过程中采用了几种新的工艺方法,其中包括二氧化硅晶体模板的应用和用NaOH溶液代替常用的HF溶液作为模板去除剂.制备的介孔二氧化钛薄膜光子晶体的面积达到厘米尺寸,二氧化钛骨架的填充率达到17.4%,薄膜制备过程中的收缩率<3%.薄膜透射光谱研究结果表明,这种大面积3D有序的反蛋白石结构介孔二氧化钛薄膜具有非常优良的光子带隙特性,有望成为一类具有非常好的发展和应用前景的光子晶体材料.     

Recent Progress in the Synthesis of Porous Carbon Materials

In this review, the progress made in the last ten years concerning the synthesis of porous carbon materials is summarized. Porous carbon materials with various pore sizes and pore structures have been synthesized using several different routes. Microporous activated carbons have been synthesized through the activation process. Ordered microporous carbon materials have been synthesized using zeolites as templates. Mesoporous carbons with a disordered pore structure have been synthesized using various methods, including catalytic activation using metal species, carbonization of polymer/polymer blends, carbonization of organic aerogels, and template synthesis using silica nanoparticles. Ordered mesoporous carbons with various pore structures have been synthesized using mesoporous silica materials such as MCM‐48, HMS, SBA‐15, MCF, and MSU‐X as templates. Ordered mesoporous carbons with graphitic pore walls have been synthesized using soft‐carbon sources that can be converted to highly ordered graphite at high temperature. Hierarchically ordered mesoporous carbon materials have been synthesized using various designed silica templates. Some of these mesoporous carbon materials have successfully been used as adsorbents for bulky pollutants, as electrodes for supercapacitors and fuel cells, and as hosts for enzyme immobilization. Ordered macroporous carbon materials have been synthesized using colloidal crystals as templates. One‐dimensional carbon nanostructured materials have been fabricated using anodic aluminum oxide (AAO) as a template.     

Highly ordered poly(thiophene)s prepared in mesoporous silica nanoparticles

Nanostructured PEDOT was synthesized using mesoporous silica as a nano-template. The polymerization of thiophene monomers was performed with an oxidant and mesoporous silica nanoparticles. The silica particles took essential role in absorbing monomers and oxidant molecules, and growth of polymers inside their pores. As prepared polymer/silica composite was treated with HF solution to remove silica template to result in 1D wire structure and mesh type porous 3D structures from SBA-15 and KIT-6 template, respectively. The average size of the poly(thiophene) wires was 10 15 nm, which was matched well to the pores size of the silica templates, as determined from an electron microscopy. At optimized condition, the room temperature electrical conductivities of the PEDOT grown from SBA-15 and KIT-6 template were similar as 1.1 and 1.0 S/cm, respectively. However, the evolution of the PEDOT conductivity versus temperature was different depending on the templates. These results gave a unique chance to tailor made 3 dimensional structure as well as properties of conductive polymer.     

Carbon-loaded porous materials produced from fine-particle silica

Carbon-loaded porous materials have been produced by modifying inorganic matrices with pyrolytic carbon prepared via polystyrene carbonization at 750°C in an argon atmosphere. The matrices have been produced from silica particles about 80 nm in size, and polystyrene has been introduced either via impregnation or using polystyrene solutions as dispersion media in the fabrication of the composites. The structure and state of the carbon formed in pores of the composites have been studied by x-ray photoelectron spectroscopy and transmission electron microscopy. The results demonstrate that the pyrolytic carbon has the form of nanotubes or segmented nanospheres.     

Synthesis of tailored porous alumina with a bimodal pore size distribution

Hierarchical channel or well-connected small and large pore networks show multiple advantages for application in catalysis or adsorbent in aqueous condition. Micro- and mesopores provide size or shape selectivity for a guest molecule, while additional macropores reduce transport limitations. In this study, we proposed a novel method to prepare bimodal porous aluminas, which have meso- and macropores with narrow pore size distribution and well defined pore channels. The framework of the porous alumina is prepared via a chemical templating method using alkyl carboxylates. Polystyrene (PS) beads are employed as a physical template for macropores. We examined polydiallyldimethylammonium chloride (PDDA)-treated aluminas as organic adsorbent in aqueous solution. Above 90% of the anionic dye (acid red 44) is removed within 10 min, and the adsorption rate of PDDA/P4 (supported on the bimodal porous alumina) is faster than that of PDDA/P2 (supported on the unimodal porous alumina) because macropore of P4 have reduced transport limitation and enhanced the accessibility to the active site of cationic charge.     

Template-directed synthesis of silica nanotubes for explosive detection

Fluorescent porous organic-inorganic thin films are of interest of explosive detection because of their vapor phase fluorescence quenching property. In this work, we synthesized fluorescent silica nanotubes using a biomineralization process through self-assembled peptidic nanostructures. We designed and synthesized an amyloid-like peptide self-assembling into nanofibers to be used as a template for silica nanotube formation. The amine groups on the peptide nanofibrous system were used for nucleation of silica nanostructures. Silica nanotubes were used to prepare highly porous surfaces, and they were doped with a fluorescent dye by physical adsorption for explosive sensing. These porous surfaces exhibited fast, sensitive, and highly selective fluorescence quenching against nitro-explosive vapors. The materials developed in this work have vast potential in sensing applications due to enhanced surface area.     

Novel Aerosol-Based Approach toward Mesoporous Silica Nanoparticles

This study introduces a novel gas-phase method for the synthesis of mesoporous silica nanoparticles (MSNs). The method is a two-step templating approach by first forming silicon-coated carbon structures in a hybrid microwave-plasma/hot-wall reactor followed by an annealing step to produce mesoporous silica with distinct nanostructure and porosity. Two different (sacrificial) carbonaceous templates have been prepared (plasma reactor) and coated (hot-wall reactor), 2D few-layer graphene (FLG) flakes and soot-like fractal aggregates. Results show that the wall thickness of the porous silica structures can be adjusted by changing the concentration of the silicon precursor (monosilane). High monosilane concentrations, however, result in solid silica particles after annealing. Using soot-like particle templates permitted to control of the shell thickness of the hollow porous particles, while the FLG template results in ultrathin silica sheets after heat treatment. The pore volume and specific surface area increase up to 263 m² g⁻¹ and 0.6 cm³ g⁻¹, respectively, by the formation of hollow porous particles. An adsorption study on carbamazepine reveals up to ≈86% removal. The gas-phase aerosol-based template method presented here offers scalability and versatility, and it is capable of producing MSNs with a controlled structure and porosity by modifying the carbonaceous templates.     

Porous carbon derived from waste polystyrene foam for supercapacitor

Polystyrene, one of the classical plastic, has caused serious environmental problems due to overuse and inability to recycle effectively. Transforming it into functional carbon materials is one of the effective ways to recycle polystyrene and other waste plastics, which has drawn the attention. In this study, we have developed a facile and efficient method for the preparation of three-dimensional (3D) network structure porous carbon (PC) via the Friedel–Crafts reaction with waste polystyrene serves as carbon source. Notably, the constructed carbonyl (–CO–) cross-linking bridges between the linear polystyrenes provide the resulting hierarchical porous polystyrene with a high cross-linking density and amounts of oxygen atoms to achieve the carbonizability of cross-linking polystyrene framework. Moreover, silica particles created more porous structure for carbon material. The prepared PC showed large specific surface area and 3D porous structure and exhibited good capacitance and electrochemical stability as electrode materials for supercapacitor.