Synthesis Of Mesoporous Materials Research Articles

Synthesis methods and applications of mesoporous and microporous materials

Over the past decades, the academic community has devoted considerable attention to mesoporous and microporous materials, primarily due to their distinctive nanoscale pore structures. Despite the extensive research conducted on these materials, there is still a pressing need to develop methods for optimizing their synthesis and improving their performance. Therefore, this paper introduces the basic concepts of mesoporous and microporous materials and their importance, and describes in detail their typical synthesis methods that include the solution-gel method for the synthesis of mesoporous materials and the ionothermal synthesis method for the synthesis of microporous materials. The paper then goes on to examine some of the more common characterization methods that are used in the field, such as X-ray diffraction (XRD), nitrogen adsorption, and transmission electron microscopy (TEM), and also lists some of the ways in which these characterization methods have been used in the context of electrochemical capacitors and photocatalytic explanation. It has been shown that mesoporous and microporous materials have the potential for significant applications in energy storage and environmental remediation. Further research should concentrate on the improvement of the synthesis process and the investigation of additional application areas, with the aim of fully exploiting the potential of these materials.

A new method for reducing impurities in clay minerals

The processing of clay minerals consists, among other steps, in the removal of isolated mineral impurities, that is, not associated to crystalline structure of clay minerals, such as fractions of quartz and feldspars, originating from the process of soil formation. Thus, this work evaluated a sustainable method to reduction of isolated mineral impurities, in 4 in natura soil samples from Maranhão/Brazil, containing clay minerals. The method consisted of dispersing the samples only in water under high rotation and separating the impurities by sieving and decanting. The water and clay fraction were recovered from a manufactured solar evaporator and the clay fraction analyzed: X-ray diffraction (XRD) revealed a reduction in the intensities of mineral impurities, largely quartz, and a significant increase in the intensity corresponding to clay minerals; X-ray fluorescence (XRF) demonstrated a decrease in the SiO2/Al2O3 ratio, indicating quartz removal; Fourier transform infrared analysis (FTIR) indicated removal of organic material; thermal analysis (TG/DTG) revealed an increase in the percentage of structural water loss, suggesting an increase in clay mineral content, and adsorption/desorption isotherms of N2 demonstrated an increase in the surface areas and adsorption capacity of the benefited samples. The process yields obtained demonstrated compatibility with the particle size of the samples, with more expressive results for the more clayey ones. Thus, the investigated method, low cost and sustainable, proved to be viable and effective in obtaining clay minerals with reduced presence of isolated impurities, promoting considerable improvements in their properties, and favoring various technological applications, such as adsorption, heterogeneous catalysis, synthesis of mesoporous materials, among others.

Synthesis of Mesoporous Silica from Palm Oil Boiler Ash (MS-POBA) with Addition of Methyl Ester Sulfonate as a Template for Free Fatty Acid Adsorption from Crude Palm Oil (CPO)

The synthesis of mesoporous material by utilizing palm oil boiler ash (POBA) waste as the silica source and methyl ester sulfonate (MES) surfactant as the template for a high-porosity was investigated for free fatty acids (FFA) adsorption. The research was initiated with silica extraction from POBA by sodium hydroxide addition through the sol-gel precipitation method. Silica modification was carried out with MES surfactant and 3-aminopropyltrimethoxysilane (APTMS) as the co-structure-directing agent (CSDA) in different calcination temperatures. Mesoporous silica-POBA (MS-POBA) free template had a surface area, pore diameter, and pore volume (41.033 m2/g, 4.180 nm, and 0.250 cm3/g) lower than MS-POBA with the template (71.0147 m2/g, 7.923 nm, and 0.524 cm3/g). The ability of MS-POBA to adsorb FFA reached its optimum conditions with an adsorption time of 20 min and an adsorbent dosage of 0.24 g. The FFA removal by MS-POBA with the template was found to have higher adsorption ability, which was 35.54%, compared to the MS-POBA free template of 26.68%. The high porosity of MS-POBA with a template makes the FFA adsorption capacity of this material higher than MS-POBA free template.

Uncovering the Recent Progress of CNC-Derived Chirality Nanomaterials: Structure and Functions.

Cellulose nanocrystal (CNC), as a renewable resource, with excellent mechanical performance, low thermal expansion coefficient, and unique optical performance, is becoming a novel candidate for the development of smart material. Herein, the recent progress of CNC-based chirality nanomaterials is uncovered, mainly covering structure regulations and function design. Undergoing a simple evaporation process, the cellulose nanorods can spontaneously assemble into chiral nematic films, accompanied by a vivid structural color. Various film structure-controlling strategies, including assembly means, physical modulation, additive engineering, surface modification, geometric structure regulation, and external field optimization, are summarized in this work. The intrinsic correlation between structure and performance is emphasized. Next, the applications of CNC-based nanomaterials is systematically reviewed. Layer-by-layer stacking structure and unique optical activity endow the nanomaterials with wide applications in the mineralization, bone regeneration, and synthesis of mesoporous materials. Besides, the vivid structural color broadens the functions in anti-counterfeiting engineering, synthesis of the shape-memory and self-healing materials. Finally, the challenges for the CNC-based nanomaterials are proposed.

Ultrasound and Microwave-Assisted Synthesis of Hexagonally Ordered Ce-Promoted Mesoporous Silica as Ni Supports for Ethanol Steam Reforming

Solvothermal synthesis of mesoporous materials based on amphiphilic molecules as structure-directing agents can be enhanced using non-conventional technologies for stirring and thermal activation. Here, we disclose a green synthesis approach for the preparation of cerium-modified hexagonally ordered silica sieves. Ultrasound micromixing enabled us to obtain well-dispersed Ce in the self-assembled silica network and yielded ordered materials with high cerium content (Ce/Si molar ratio = 0.08). Microwave dielectric heating, applied by an innovative open-end coaxial antenna, was used to reduce the overall hydrothermal synthesis time and to improve the surface area and textural properties. These mesoporous materials were used as a Ni catalyst support (10 wt.% metal loading) for the ethanol steam reforming reaction. The new catalysts featured complete ethanol conversion, high H2 selectivity (65%) and better stability, compared to the same catalyst prepared with magnetic stirring and conventional heating. The Ce-promoted silica sieves offered a suitable support for the controlled growth of nanocarbon that does not result in catalyst deactivation or poisoning after 6 h on stream.

Synthesis of Nb/MCM-48 material using rice husk ash as silica source with different SI/NB molar ratios

The large amount of rice produced in Brazil generates a large volume of co-products, such as, Rice Husk (RH) and Rice Husk Ash (RHA). These co-products have amounts of silicon (Si) present in their structure, which can be used to synthesize silica-based materials as zeolites and MCM-type structures. The synthesis of MCM-48 material was carried out at room temperature, using the ionic liquid [C16MI·Cl] as structure-directing agent, depositing the niobium in situ during the synthesis with different molar ratios of Si/Nb (5, 20, 50 and 80). The material obtained was subjected to characterization by X-Ray Diffraction (XRD), Nitrogen Adsorption/Desorption isotherms and Scanning Electron Microscopy (SEM). The results confirm the formation of Nb/MCM-48 materials, in which their properties are consistent with those described in the literature. The deposition of Nb on MCM-48 did not change its structural properties, such as specific surface area and pore distribution for Si/Nb higher than 5. The results obtained demonstrate the success in the synthesis of mesoporous materials Nb/MCM-48 using industrial residues of rice as an alternative source of silicon, and in situ deposition of the niobium metal on the structure.

Recent advances in the synthesis of mesoporous materials and their application to lithium-ion batteries and hybrid supercapacitors

The ever-growing demand for high performance energy storage systems has fueled the development of advanced electrode materials with light weight, high energy/power densities, and stable cycle life. Mesoporous materials play an important role in achieving these goals because of their unique features such as high surface area, tunable pore size, pore volume, and pore structures, as well as adjustable particle size and morphology. In this review, we summarize the recent progress in the synthesis of mesoporous materials and their applications in lithium-ion batteries (LIBs) and lithium-ion hybrid supercapacitors (Li-HSCs) over the past ten years. The block copolymer guided soft-template route is highlighted as a simple and versatile tool for designing mesoporous materials with controlled nano-and macrostructures without complicated synthetic procedures. The structural/morphological benefits of designed mesoporous materials translate into highly improved electrochemical performance in LIBs and Li-HSCs. Finally, future challenges and perspectives on the development of mesoporous materials in energy storage devices are provided, which will be useful both in academia and in industry.

Effect of Parameters of Synthesis of Mesoporous Materials on the Set of Their Sorption–Texture Properties

The effect of technological parameters on the morphological and sorption-structural characteristics of mesoporous materials is described. Recommendations on the production of such materials with narrow and bimodal pore size distribution and the maximum possible specific surface area on the example of the MCM-41 template synthesis are provided.

Electrodeposition of Mesoporous Ni-Rich Ni-Pt Films for Highly Efficient Methanol Oxidation.

The use of soft templates for the electrosynthesis of mesoporous materials has shown tremendous potential in energy and environmental domains. Among all the approaches that have been featured in the literature, block copolymer-templated electrodeposition had robustness and a simple method, but it practically cannot be used for the synthesis of mesoporous materials not based on Pt or Au. Nonetheless, extending and understanding the possibilities and limitations of block copolymer-templated electrodeposition to other materials and substrates is still challenging. Herein, a critical analysis of the role of the solution’s primary electroactive components and the applied potential were performed in order to understand their influences on the mesostructure of Ni-rich Ni-Pt mesoporous films. Among all the components, tetrahydrofuran and a platinum (IV) complex were shown to be crucial for the formation of a truly 3D mesoporous network. The electrosynthesized well-ordered mesoporous Ni-rich Ni-Pt deposits exhibit excellent electrocatalytic performance for methanol oxidation in alkaline conditions, improved stability and durability after 1000 cycles, and minimal CO poisoning.

Study on the synthesis of mesoporous materials with liquid crystals formed in SDS/CTAB/NaBr/1-Hexanol/H2O as templates

Mesoporous silica materials were synthesized using tetraethoxysilane (TEOS) as precursor and liquid crystals (LCs) formed in mixtures of cationic cetyltrimethylammonium bromide (CTAB) and anionic sodium dodecyl sulfate (SDS) with additions of NaBr and 1-hexanol as templates. For this purpose, the formation of LCs in the mixtures under different conditions was first studied. It was found that the additions of 1-hexanol and NaBr can synergistically weaken the electrostatic interaction between CTAB and SDS and promote the growth of the ordered assemblies, leading to the significant expansion of the LC phase areas in both SDS excess area and CTAB excess area, respectively. The effects of 1-hexanol concentrations, surfactant concentrations, and pH values on the phase diagram and hence the structures of LCs were subsequently studied. These LCs are well-structured templates for the syntheses of mesoporous silica materials that were characterized using nitrogen adsorption/desorption analysis and scanning electron microscopy (SEM). It was shown that 1-hexanol played an important role in the formation of LC templates and hence effectively improved the specific surface area and order of mesoporous materials. The BET specific surface area was high up to 937 m2/g and the average pore diameter increased to 2.5 nm when the total concentration of CTAB and SDS was 0.2 mol/L, the molar fraction of CTAB in the mixture was 0.82, the concentration of 1-hexanol was 0.4 mol/L, and pH value was 2. These studies shed light on the syntheses of mesoporous materials with large specific surface area and highly ordered structure for multiple applications.

An imidazolium ionic liquid as effective structure-directing agent for the fabrication of silica thin films with vertically aligned nanochannels

In parallel to the increasing variety of ionic liquids that show different kinds of nanometer-scale structuration in their pure and solved forms, there is a raising interest in exploring the possibility of using ionic liquids as soft-templates for the synthesis of mesoporous materials. We report the case of 1-hexadecyl-3-methylimidazolium chloride (C16MIMCl), a surface active ionic liquid (SAIL), here used as an excellent soft-template for the formation of vertically aligned, uniform mesochannels, with a well defined pore width of 2.5 nm in silica thin films deposited with the electrochemically assisted self-assembly (EASA) method. The obtained mesochannels run through the entire thickness of the films and after removal of the ionic liquid the emptied mesochannels ensure a thorough mass transport to the substrate, here monitored by the redox-active electrochemical probe Ru(II)/Ru(III) during cyclic voltammetry (CV). Moreover, the mechanism of pore formation is explained; unlike the mechanisms reported for short chain imidazolium ionic liquid silica templates, in the case of C16MIMCl the dominating so-called cooperative interaction is the electrostatic attraction between the C16MIM+ and the network-forming negatively charged silicate oligomers. Therefore, this study provides a better understanding of the templating behavior of long chain imidazolium ionic liquids and motivates further research on the synthesis of ionic liquid-based functional hybrid materials.

Preparation and adsorption properties of mesoporous material PS-MCM-41 with low-silicon content peanut shell ash as silicon source

The toxic and costly chemicals are usually used as the source of silicon for the synthesis of mesoporous materials. In this paper, the mesoporous material PS-MCM-41 was synthesized by hydrothermal synthesis, in which low-silicon content peanut shell ash is used as the silicon source. The properties of the obtained material were confirmed by N2 physical adsorption, X-ray diffraction (XRD), SEM, TEM, and FTIR. The adsorption performance was evaluated during the adsorption experiment of crystal violet dye and compared with that of the mesoporous material MCM-41. The results showed that the peanut shell ash as silicon source could be used to successfully synthesize the mesoporous material PS-MCM-41. The adsorption efficiency of PS-MCM-41 to 50 mg/L crystal violet solution reached 99.90%, and the adsorption efficiency of PS-MCM-41 to 800 mg/L crystal violet solution reached 84.2%. Compared with MCM-41 and other adsorbents, PS-MCM-41 exhibited excellent adsorption properties and adsorption capacity for crystal violet. The adsorption kinetic data showed that the pseudo-secondary equation could better explain the adsorption data of the adsorption crystal violet. The adsorption isotherm model was consistent with the Langmuir model (R2> 0.99) with maximum adsorption capacities of 1428.57 mg/g.

Polyethylene glycol/silica (PEG@SiO2) composite inspired by the synthesis of mesoporous materials as shape-stabilized phase change material for energy storage

Inspired by the common preparation method of mesoporous silica where polyethylene glycol (PEG) was used as template to obtain porous silica, PEG/silica (PEG@SiO2) composite as shape-stabilized phase change material for energy storage was well prepared. In this paper, PEG was used as phase change material (PCM) to store and release thermal energy and SiO2 acted as the supporting matrix. Various techniques were employed to characterize the structural and thermal properties of PEG@SiO2. The results indicate that PEG was encapsulated in SiO2 shell with physical interactions. The phase change enthalpy of PEG@SiO2 is 164.9 J/g in the melting process and 160.1 J/g in the solidifying process with the mass fraction of 97 wt%. It is a considerably exciting result as the value is so close to pristine PEG’s (178.6 J/g). PEG@SiO2 exhibited excellent thermal reliability based on the results of undergoing the heating-cooling cycle 100 times. Also, PEG@SiO2 had a good thermal stability within its working temperature range. This study provides a general approach for increasing the loading of PCMs in porous materials and thus the energy storage capability.

Influence of Change of Si/Al Ratio on the Synthesis of Mesoporous Aluminosilicates and Flexural Strength of Novolac Composites

Fillers used in phenol–formaldehyde resins should have high thermal stability, be cheap and do not have a negative impact on the resin crosslinking process. These features have mesoporous aluminosilicates which are used in many industries. In this work, effective and simple synthesis of mesoporous materials (with a different Si/Al ratio) from a solid source of silicon has been presented. Materials were used as fillers for phenol–formaldehyde composites. Synthesized mesoporous aluminosilicates have been characterized using Scanning electron microscopy, Energy dispersive spectrometry, Transmission electron microscopy, X-ray Difractometry, Nitrogen adsorption/desorption measurements and Inverse gas chromatography. The properties of the obtained materials are closely related to the amount of aluminum and silicon in the tested materials. All synthesized materials have a larger specific surface area than the substrates used during the synthesis. The mechanical properties of the novolac composites were tested using three-point flexural test. The composite with aluminosilicate which have the lower surface area has the highest flexural strength and it is higher than the strength of the composites with substrates.

Development of Silica-Based Monoliths for the Capture of CO2

The synthesis of mesoporous materials in macroscopic scale, as for example, the monoliths, has been of great interest in view of the wide range of applications that this material holds. Thus, this work consists of the production of silica monoliths for the purpose of they being used in the carbon dioxide (CO2) adsorption process. The adsorbents were prepared in pure form and also with addition of heteroatoms: Al, Ti and Zr. The samples were then functionalized with pentaethylenehexamine (PEHA) by the wet impregnation method. The materials were characterized by the following techniques: X-ray diffraction (XRD), textural analysis, Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM) and Thermogravimetry (TG/DTG). The analyses indicated that the materials synthesized with heteroatom incorporation presented a disordered pore structure and high surface area (1387 m2/g for sample Ti/M1). In addition, they showed a significant increase in adsorption of CO2 relative to their parent sample, a fact that is not much explored in the literature. The CO2 adsorption performance tests were carried out at 30 oC and atmospheric pressure. All functionalized materials demonstrated improved CO2 adsorption capacity relative to their starting samples. Adsorption capacities up to 111.3 mg/g were found in this work, which makes the materials developed promising candidates for the capture of CO2.

A Novel Iron Silicate Mesoporous Material Synthesis and Its Characterization

The mesoporous materials have variety of applications in several field particularly it has a main role in Catalysis, Petrochemical industries and Adsorption. Normally the porous material has well ordered 3Dimensional structure, huge surface area, high thermal stability and active acid sites. The properties of these materials can be varied because it is mostly depends on its template, synthesis method and isomorphous substitution of metal ions. There are two major mesoporous materials which are aluminosilicate and aluminophosphate. In this present investigation AlCl3 and FeCl3 are used in equal amount for the synthesis of mesoporous material. The synthesized material is characterized by FT-IR, XRD, TGA, BET, EDAX and TPD. Morphological images were studied by SEM. These characterization techniques confirm the formation of mesoporous molecular sieves.

Dendrimers as alternative templates and pore-directing agents for the synthesis of micro- and mesoporous materials

Dendrimers have been used to control the pore size and morphology of porous materials during their synthesis. Various characterization techniques have also been used to validate the formation of mesoporosity. Materials such as cetyltrimethylammonium bromide (CTAB) and other co-polymers are commonly used as templates for the synthesis of mesoporous materials. However, advantages of using dendrimers as templates for the synthesis of mesoporous materials include: (1) ease of control of the final pore size (depending on the dendrimer employed); (2) ease of removal of the dendrimer template by a simple extraction method or calcination process, which does not strongly interact with the inorganic species; (3) the monodispersed structure of the dendrimer leads to the formation of monodispersed pores with a narrow size distribution; and (4) the synthetic process require room (or relatively low) temperatures as opposed to elevated temperatures used for other surfactants. This mini-review is therefore focussed on the use of dendrimers as templating or pore-directing agents for the synthesis of micro- and mesoporous materials. The catalytic application of the mesoporous materials as heterogeneous supports is also discussed.

Synthesis of mesoporous materials from bamboo leaf ash and catalytic properties of immobilized lipase for hydrolysis of rubber seed oil

Mesoporous MCM-41 was synthesized via the extraction of silica from bamboo leaf ash and used as a support matrix for the immobilization of lipase to hydrolyze rubber seed oil. The effect of extraction parameters on MCM-41 synthesis was evaluated using Central Composite Design (CCD). More than 85% silica recovery from bamboo leaf ash was obtained for an extractant to ash weight ratio – 1.75 (wt/wt), ultra-sonication time – 8 h and temperature – 80 °C). Lipase from porcine pancreas (triacylglycerol ester hydrolase, EC 3.1.1.3) was immobilized on the synthesized MCM-41. Approximately 73% hydrolysis was obtained at an immobilized lipase loading of 100 mg and water content – 20v/v % at room temperature (35 °C). Less than 15% reduction in percent hydrolysis of rubber seed oil even after 15 cycles of reuse suggested the effectiveness of the reused catalyst.

General Syntheses of Nanotubes Induced by Block Copolymer Self-Assembly.

Amphiphilic block copolymer templating strategies are extensively used for syntheses of mesoporous materials. However, monodisperse tubular nanostructures are limited. Here, a general method is developed to synthesize monodisperse nanotubes with narrow diameter distribution induced by self-assembly of block copolymer. 3-Aminophenol (AP) and formaldehyde (F) polymerize and self-assemble with cylindrical PS-b-PEO micelles into worm-like PS-b-PEO@APF composites with uniform diameter (49 ± 3 nm). After template extraction, worm-like APF polymer nanotubes are formed. The structure and morphology of the polymer nanotubes can be tuned by regulating the synthesis conditions. Furthermore, PS-b-PEO@APF composites are uniformly converted to isomorphic carbon nanotubes with large surface area of 662 m2 g-1 , abundant hierarchical porous frameworks and nitrogen doping. The synthesis can be extended to silica nanotubes. These findings open an avenue to the design of porous materials with controlled structural framework, composition, and properties for a wide range of applications.

Molecular Design of Bisphosphonates To Adjust Their Reactivity toward Metal Sources for the Surfactant‐Assisted Synthesis of Mesoporous Films

AbstractThe precise control of primary reactions in solutions is one of the most significant steps for the nanoscale design of inorganic solids in multidisciplinary fields. However, further growth of the inorganic species to give bulkier species disturbs such designs. The surfactant‐assisted synthesis of mesoporous materials is a good strategy for addressing such concerns because pores formed by supramolecularly mediated processes are surrounded by nanometer‐sized continuous frameworks. Many experiments are generally conducted to optimize the reaction conditions for the synthesis of highly ordered mesostructures. Herein, to minimize such trial‐and‐error efforts, a new and practical concept is proposed for the precise design of porous materials. By adjusting the reactivity between bisphosphonates and metal sources through molecular design of the starting bisphosphonate compound, it was possible to synthesize mesoporous films with unique compositions by a surfactant‐assisted approach.