Fibrous Silica Nanospheres Research Articles

Thiophene desulfurization: Effects of dendritic silica and PEG as surface modifier on ZnO photocatalyst

This work focused on desulfurizing thiophene using a photocatalyst comprising zinc oxide (ZnO) and fibrous silica nanospheres (KCC-1) to exploit the photocatalytic process. Six photocatalyst samples (commercial ZnO, KCC-1, ZnO/1.5KCC-1, ZnO/2.0KCC-1, ZnO/2.5KCC-1 and ZnO/PEG) were characterized using field-emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR) spectroscopy and X-ray diffractometry (XRD). It was found that the properties of ZnO were altered by incorporating KCC-1 to enhance the efficiency of thiophene desulfurization. Desulfurization performances were investigated using three parameters, which were initial pH, initial thiophene concentration, and photocatalyst loading. Each parameter was validated using thiophene desulfurization percentage and turbidity removal percentage. This work discovered that ZnO/2.0KCC-1 was the optimum photocatalyst with 83 % thiophene desulfurization. No clear trend was observed for turbidity removal percentage, yet the ZnO/KCC-1 photocatalyst was able to reduce turbidity significantly. The pH of the permeation rose from neutral to alkaline range due to the hydroxyl radicals (•OH) produced during the desulfurization process.

Rational design of silica nanoreactor encapsulated Ni for reinforcing coke-resistance in dry reforming of methane

Dry reforming of methane (DRM) provides a desired approach to produce valuable syngas in tackling greenhouse gases. Yet it faces a formidable challenge in the design and synthesis of high coke-resistant Ni-based catalysts. Herein, we report a nanoreactor strategy to construct a supported Ni catalyst (Ni@SiO2@SiO2) for reinforcing coke-resistance during DRM, by effectively encapsulating small Ni nanoparticles into dendritic fibrous silica (SiO2) nanospheres and coating SiO2 shell layers. Taking advantage of chemical characteristics of citric acid (CA), CA-chelated Ni impregnation enables the uniform immobilization of Ni species into the radial SiO2 framework, then following carbonization produces protective carbon layers on the Ni nanoparticle surface during SiO2 coating, which can be removed via oxidizing calcination. The resultant pomegranate-like nanoreactor catalyst possesses outstanding coke-resistance, without any detectable coke deposition after 200 h of DRM reaction at 700 ℃, benefiting from effectively restricting metal sintering and fully preventing formation of inert carbon species.

A comparative study of fibrous silica-based catalysts for improving methane production via CO2 methanation

The process of utilizing the greenhouse gas carbon dioxide (CO2) is crucial in addressing and reducing the impact of climate change. The CO2 methanation process, also known as the Sabatier reaction, is considered one of the appealing approaches since it provides synthetic natural gas (SNG), fulfilling the present needs. However, the CO2 methanation reaction demands an exceptionally effective catalyst capable of surpassing the energy barrier associated with eight proton-electron transfers from H2 molecules. Herein, the application of fibrous silica nanospheres along with the fibrous modification of mesostructured silica nanoparticles (MSN) towards CO2 methanation, called the Centre of Hydrogen energy silica (CHE-Si) and CHE-SM was reported. Both catalysts were successfully synthesized by utilizing micro-emulsion techniques and subsequently were characterized with x-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, and N2 adsorption-desorption. FTIR results revealed that CHE-SM possessed superior Si-OH and Si-O species than CHE-Si despite displaying low surface area and pore volume. Consequently, CHE-SM achieved above 50% CO2 conversion and CH4 yield at 500 °C while CHE-Si exhibited lower performance. This discrepancy in catalytic performance was due to the fact that CHE-SM was comprised of more active sites that could adsorb and dissociate CO2 and H2 reactants.

Preparation of a magnetic molecularly imprinted polymer on fibrous silica nanosphere via self-polycondensation for micro solid-phase extraction of chlorpyrifos

Throughout this research, a new magnetic molecularly imprinted polymer on fibrous silica nanosphere was prepared through self-polycondensation. The selective extraction of chlorpyrifos was performed by the synthesized sorbent and as a determination system, a gas chromatography-electron capture was applied. The formation of sorbent was confirmed through the use of Fourier transform infrared spectroscopy and field emission scanning electron microscopy techniques. The parameters affecting the extraction efficacy of the proposed method were scrutinized in an optimized way. The linear range and the detection limit of the studied method were 0.003–0.3 and 0.001 ng mL−1, respectively. The relative standard deviations were 4.1–5.2 and 5.6–7.6 % for intra- and inter-day (n = 3), respectively. To assess the performance of the proposed method, some water and fruit samples were analyzed and the extraction recoveries of 83–109 % were obtained. These results revealed the method's performance in the analysis of chlorpyrifos in real samples.

Highly efficient immobilized PN3P-pincer iridium catalyst for dehydrogenation of neat formic acid

Formic acid (FA) has been well recognized as one of the most promising hydrogen carriers. The dehydrogenation of the FA could offer an efficient process to on-demand hydrogen generation with a suitable catalyst. Homogeneous catalysts have demonstrated superior activity and selectivity compared to traditional heterogeneous catalysis. However, the latter is preferred for large-scale applications. By incorporating the homogeneous organometallic complex onto an appropriate support, the unique features of both types of catalysts can be combined and utilized effectively. Herein, we synthesized an immobilized PN3P-Ir pincer catalyst (2) supported onto KCC-1, a 3D fibrous silica nanosphere that exhibits a high surface area and contains a tetracoordinate aluminum site. To reduce the use of volatile additives, the choice of cesium formate (CsO2CH) was found to be crucial as at 80–90 °C, CsO2CH could act as a reaction medium and serve as basic additive. Remarkable reactivities under neat conditions were achieved with a TOF of 13,290 h-1 and a TON of up to 540,000. The comparative study indicates a significant improvement of 2 from its homogenous counterpart, PN3P-IrH3 (1).

Formic Acid Dehydrogenation via an Active Ruthenium Pincer Catalyst Immobilized on Tetra-Coordinated Aluminum Hydride Species Supported on Fibrous Silica Nanospheres

Formic Acid Dehydrogenation via an Active Ruthenium Pincer Catalyst Immobilized on Tetra-Coordinated Aluminum Hydride Species Supported on Fibrous Silica Nanospheres

Intersperse copper nanoparticles into 3D fibrous silica-supported carbon spheres for electrocatalytic nitrogen reduction

The electrocatalysts are critical to the electrocatalytic nitrogen reduction reaction (e-NRR) technique and its development. Herein, through morphological structure modulation, three-dimensional (3D) fibrous silica nanospheres (KCC-1) are firstly fabricated as the supporting scaffold, followed by the coating of nitrogen-doped carbon and interspersing of copper nanoparticles. The resulting carbon spheres (KNC) has very uniform interspersion of copper nanoparticles (Cu-NPs) in the 3D fibrous structure ensuring high accessible active sites for nitrogen molecules; the thin surface carbon layer offering a rich channel for electron transport; and nitrogen dopant allowing efficient electron transfer of copper atoms throng metal-nitrogen covalent bonds. When used as electrocatalysts to e-NRR, KNC exhibits good electrochemical activity, selectivity, and good stability, and can obtain an ammonia yield of approximately 6.67 µg h−1 mgcat−1 and an excellent Faraday efficiency (FE) of 8.1% in 0.1 M sodium sulfate solution at − 0.4 V (vs. RHE).

Compositional study of plasmalogens in clam (Corbicula fluminea) by TiO2/KCC-1 extraction, enzymatic purification, and lipidomics analysis

In this study, the plasmalogens in clam (Corbicula fluminea) were extracted by titanium dioxide (TiO2) fibrous silica nanosphere (KCC-1) extraction and phospholipase A1 hydrolysis. The molecular composition of plasmalogens was lipidomically analyzed using hydrophilic interaction chromatography mass spectrometry (HILIC-MS). The results showed that there was a total of 34 plasmalogen molecular species structurally elucidated. The quantitative results of linear regression models indicated that plasmenylcholine (14.24 μg mg–1) was the most abundant class, followed by plasmenylethanolamine (11.25 μg mg–1), and plasmenylserine (9.78 μg mg–1). Multivariate data analysis was applied to reduce data dimensions and circos map was used to provide an integrated and holistic view of correlation coefficients between the samples and plasmalogen molecular species. This method was validated to be accurate and sensitive in extraction and analysis of plasmalogens in clams.

Covalent triazine-based framework-grafted functionalized fibrous silica sphere as a solid-phase microextraction coating for simultaneous determination of fenthion and chlorpyrifos by ion mobility spectrometry.

A novel covalent triazine-based framework (CTF)-grafted phenyl-functionalized fibrous silica nanosphere, KCC-1 (named as RS-2) was synthesized via a simple and effective Friedel-Crafts approach. The microporous CTF with fluorene backbone was coupled and grown uniformly on the surface of phenyl-functionalized KCC-1 to prepare a hybrid extended porous framework. The prepared materialswere characterized, and FE-SEM and TEM images revealed a flower-like structure for RS-2. The synthesized RS-2 showed excellent thermal stability, so the weight loss was about 30% at 800°C. RS-2 was applied as a new coating in the solid-phase microextraction procedure to extract chlorpyrifos and fenthion pesticides fromwater, wastewater, and fruit samples, before determining by corona discharge-ion mobility spectrometry. Some experimental factors affecting the extraction yield of the analytes, including ionic strength, stirring rate, sample pH, extraction temperature, and extraction time, were investigated. Under optimum conditions, the linear dynamic ranges were 0.1-10μgL-1 and 1.0-70μgL-1, and the limits of detection were 0.05 and 0.55μgL-1 for chlorpyrifos and fenthion, respectively. The proposed method showed recovery values in the range 86-117% with a precision of 3.0-7.1% for real samples. Covalent triazine-based framework (CTF)-grafted phenyl-functionalized fibrous silica nanosphere (named as RS-2) was synthesized. RS-2 was applied as a sorbent for solid-phase microextraction (SPME) of chlorpyrifos and fenthion from fruit and water samples followed by corona discharge ionization ion mobility spectrometry (CD-IMS).

Heterogeneous activation of peroxymonosulfate with cobalt incorporated fibrous silica nanospheres for the degradation of organic pollutants in water

For activation of peroxymonosulfate (PMS) into reactive oxygen species (ROS), the catalysts with highly exposed active sites and improved mass transfer efficiency is desirable. Herein, cobalt incorporated fibrous silica nanospheres (Co-X/KCC-1) were fabricated by a one-step hydrothermal procedure and used for the first time for PMS activation to degrade phenol and other organic pollutants. In 9.0 minutes, Phenol degradation in the Co-30/KCC-1/PMS process, adsorption, sole PMS, and KCC-1/PMS processes reached almost 100%, 3.91%, 15% and 17% respectively. Moreover, 0.01 mg L−1 of Co was leached from Co-30/KCC-1 during reaction. Morphology, structure, texture, and catalytic activity of Co-30/KCC-1 were well-retained after recycling. The use of EPR and scavengers indicated that SO4−, OH, 1O2, and O2− were produced during catalysis with contribution in the order of 1O2 > O2− > SO4− >OH. In-situ ATR-FTIR, EIS, and XPS showed that the surface complex, and redox couple (Co(II)/Co(III) were responsible for the efficient ROS generation. The high catalytic activity was attributed to highly exposed active sites, radially oriented fibrous morphology, improved textural properties, and the generation of ROS. This research may provide an insight into the use of other metal/metal oxides (Fe, Mn, Cu) incorporated KCC-1 for PMS activation.

Effective and selective direct aminoformylation of nitroarenes utilizing palladium nanoparticles assisted by fibrous-structured silica nanospheres

Palladium nanoparticles (~ 1–3 nm, 0.4 wt% Pd) were uniformly distributed over the surface of fibrous silica nanospheres (KCC-1) modified via aminopropyltriethoxysilane using a fast and cost-effective palladium (II) chloride reduction process. The Pd nanoparticles (Pd NPs) distribution over the ensuing catalyst Pd/KCC-1-NH2 showed much more uniform distribution, and smaller size compared with the tedious hydrothermal reduction method. The morphological, chemical, and size analyses of Pd/KCC-1-NH2 by BET, UV–Vis spectra, XRD, HR-TEM, EDS and XPS analysis revealed that the succeeding material consist of a distinct fibrous silica nanospheres support adorn with Pd NPs. The resultant nanocatalyst was tested for the one-step reductive aminoformylation of aromatic nitro compounds using formic acid. A wide range of substituted nitroarenes including electron withdrawing, releasing, sterically hindered and multifunctional groups have been converted to corresponding aryl formamide in quantitative yields (yields up to 98%) at moderate temperature (70 °C). Optimization study has proved that the 6 equivalent of formic acid is required and toluene was found to be the better solvent. The established practice is beneficial due to the use of formic acid as H2 source and formylating agent, easiness in handling of the catalyst and simple workup procedure with efficient catalyst reusability.

Catalytically Active Co−Nx Species Stabilized on Nitrogen‐doped Porous Carbon for Efficient Hydrogenation and Dehydrogenation of N‐heteroarenes

AbstractThe development of bifunctional, highly active and stable non‐noble‐metal catalysts is important for synthetic chemistry. In this study, a highly dispersed Co catalyst stabilized on the mesoporous N‐doped carbon layers was prepared by adsorption and pyrolysis of cobalt complex on dendritic fibrous silica nanospheres (KCC‐1@Co−N−C−T). The characterizations of HAADF‐STEM, XRD and XPS together with the KSCN poisoning tests determine the absence of Co0 or CoOx nanoparticles and suggest that the Co−Nx species are the active sites. The formation of Co−Nx species results from the properties of N‐rich cobalt‐phenanthroline complex and dendritic fibrous silica supports, increasing the original spatial distance between Co atoms and thus preventing them from aggregation. The KCC‐1@Co−N−C‐800 catalyst showed excellent activity and selectivity for the oxidative dehydrogenation (ODH) of saturated N‐heterocycles and base‐free catalytic transfer hydrogenation (CTH) of unsaturated N‐heterocycles.

Constructing highly dispersed Ni based catalysts supported on fibrous silica nanosphere for low-temperature CO2 methanation

In this work, we reported that the fibrous silica nanosphere, also called as KCC-1, was facilely synthesized by the improved microemulsion hydrothermal fabrication strategy. The obtained KCC-1 was investigated as the support of the Ni based catalysts toward CO2 methanation. The obtained catalysts with unique dendrimeric mesopore structure and outstanding structural properties could provide easily accessible as well as highly dispersed Ni nanoparticles to the gaseous reactants. Besides, the Ni based catalysts with commercial SiO2 and MCM-41 as supports were also prepared as the reference catalysts to demonstrate the advantages of the dendrimeric mesoporous channels. Various techniques, such as X-ray powder diffraction (XRD), N2 physisorption, transmission electron microscopy (TEM), H2 temperature programmed reduction (H2-TPR), CO2 temperature programmed desorption (CO2-TPD), X-ray photoelectron spectroscopy (XPS), etc., were used to characterize the catalytic supports and corresponding catalysts. It was found that the metallic Ni nanoparticles could be highly dispersed over the catalysts supported on fibrous KCC-1 with dendrimeric mesoporous channels. Furthermore, the catalytic performances toward CO2 methanation had been further evaluated over these catalysts at different temperatures. It was found that the KCC-1 supported catalyst performed much higher low-temperature catalytic activities than the reference catalysts supported on commercial SiO2 and MCM-41, suggesting that the fibrous and dendrimeric mesoporous channels displayed distinctive advantages by accommodating enough metallic Ni active sites. The kinetic study also revealed that the topology of the mesoporous channel could obviously influence the apparent activation energy in the CO2 methanation reaction. Besides, the temperature programmed surface reaction (TPSR) and in-situ Diffused Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) of the CO2 methanation were also carried out to reveal the possible reaction pathway and mechanism. We also found that the fibrous silica nanosphere (KCC-1) supported catalyst demonstrated much better sintering-proof property of the metallic Ni nanoparticles than the reference catalysts during the 40 h stability tests at 400 °C. Therefore, the present fibrous silica nanosphere (KCC-1) could be considered as the promising support for Ni based catalysts toward CO2 methanation.

Corrigendum to “One-pot synthesis of functionalized mesoporous fibrous silica nanospheres for dye adsorption: Isotherm, kinetic, and thermodynamic studies” [J. Mol. Liq. 300 (2020) 112367

Abstract In this corrigendum, we present corrections to our published article “One-pot synthesis of functionalized mesoporous fibrous silica nanospheres for dye adsorption: isotherm, kinetic, and thermodynamic studies” [J. Mol. Liquids 300 (2020) 112367]. Corrections include the highlights section and three references that incorrectly listed in the references list.

Fe-based N-doped dendritic catalysts for catalytic ammoxidation of aromatic aldehydes to aromatic nitriles

Non-noble-metal-based catalysts for catalyzing the oxidative coupling of aldehydes and ammonia represent an efficient atom-economical synthetic route to produce nitriles. In this study, an effective Fe-modified N-doped carbon catalyst anchored on fibrous silica nanospheres (Fe-N/KCC-1-T) was successfully prepared by a facile strategy. 1,10-Phenanthroline with a strong chelating ability ensured the homogeneous, ultrafine distribution of Fe-based active sites, and the KCC-1 support material effectively enhanced the accessibility to these active sites, which corresponded to center-radial pore channels and a high surface area. As-fabricated Fe-N/KCC-1-T exhibited excellent catalytic performance for the ammoxidation of aldehydes under mild reaction conditions. A series of functionalized aldehydes were efficiently oxidized into the corresponding nitriles by using air as the green oxidant. Moreover, the catalyst was recycled for at least five runs without any clear decrease in the performance. Hence, this study is expected to provide an eco-friendly synthetic route to produce nitriles from easily available aldehydes and ammonia by using a cost-effective catalyst.

Protection of lithium anodes by fibrous silica nanospheres.

Lithium metal (anode) has attracted significant attention for use in lithium-metal batteries due to its high energy density, but its practical application is still hindered by the dendrite growth during the battery charging process. Here, fibrous silica nanospheres were prepared via a direct hydrothermal reaction and coated on a separator to form a composite electrode with lithium sheets. Upon using this composite electrode in a symmetrical cell, the charge and discharge curves became more stable and the overpotential was alleviated compared with that of the bare lithium metal electrode. Meanwhile, the coulombic efficiency obtained from the Li‖Cu cell remained above 95.9% after 200 cycles at 0.5 mA h cm−2. The validity of using this composite electrode in the Li‖LFP (LiFePO4, lithium iron phosphate) cells was also evaluated. The results show that the composite electrode can help restrict the growth of lithium dendrites and the accumulation of dead lithium.

One-pot synthesis of functionalized mesoporous fibrous silica nanospheres for dye adsorption: Isotherm, kinetic, and thermodynamic studies

Herein, for the first time, a novel adsorbent, 3-mercaptopropyltrimethoxysilane-functionalized mesoporous fibrous silica nanospheres, was synthesized via a one-pot synthesis route. The synthesis method provided an efficient single-step procedure to fabricate an organofunctionalized fibrous silica-based adsorbent. The structure of the prepared adsorbent material was fully characterized by FT-IR, PXRD, FE-SEM/mapping, TEM, and nitrogen adsorption/desorption analyses. Structural investigations revealed that the material possesses a bimodal micro-/mesostructure architecture with a low ordering of silica material. Also, the adsorbent showed a uniform flower-like nanospheres with wrinkled surfaces and a relatively high surface area (250 m2 g−1). The adsorption performance of the material toward crystal violet as a toxic cationic dye was studied. The influence of various parameters including pH, adsorbent dosage, initial dye concentration, contact time, and solution temperature, on the adsorption process, was systematically monitored. Non-linear forms of various kinetic and isotherm equations models were used to investigate the adsorption behavior of crystal violet onto the material. The isotherm data were fitted best to the Langmuir model with a maximum adsorption capacity of 164.3 mg g−1. Kinetic, isotherm, and thermodynamic studies demonstrated that the material can be applied as a promising adsorbent for the removal of toxic dyes from aqueous samples.

Silica Supported MgO as An Adsorbent for Precombustion CO2 Capture

MgO-silica nanocomposites were synthesized by dispersing MgO on three different silica supports, viz., ordered mesoporous MCM-41, SBA-15, and the nonporous fibrous silica nanospheres material (KCC-...

Synthesis and characterization of novel N-methylimidazolium-functionalized KCC-1: A highly efficient anion exchanger of hexavalent chromium

A key challenge in adsorption process of toxic organic and inorganic species is the design and development of adsorbent materials bearing an abundance of accessible adsorption sites with high affinity to achieve both fast adsorption kinetics and elevated adsorption capacity for toxic contaminants. Herein, a novel anion-exchange adsorbent based on fibrous silica nanospheres KCC-1 was synthesized by a facile hydrothermal-assisted post-grafting modification of KCC-1 with 1-methyl-3- (triethoxysilylpropyl)imidazolium chloride for the first time. Silica fibers with micro-mesoporous structure display the proper combination of features to serve as a potential scaffold for decorating adsorption sites to create desired ion-exchange adsorbent. The obtained N-methylimidazolium-functionalized KCC-1 (MI-Cl-KCC-1) with fibrous nanosphere morphology showed a high surface area (∼241 m2 g−1) and high pore volume (0.81 m2 g−1). The adsorption behaviors of toxic hexavalent chromium from aqueous media by the MI-Cl-KCC-1 were systematically studied using the batch method. The adsorption rate was relatively fast, and MI-Cl-KCC-1 possesses a high capacity for the adsorption of Cr(VI). The maximum Cr(VI) adsorption was obtained at pH 3.0–4.0. Different non-linear isotherm equations were tested for choosing an appropriate adorption isotherm behavior, and the adsorption data for MI-Cl-KCC-1 were consistent with the Langmuir model with a maximum adsorption capacity of 428 ± 8 mg g−1.

Triamino-anchored KCC-1: A novel and promising adsorbent for fast and highly effective aqueous CrVI removal

Triamino-anchored monodispersed fibrous silica nanospheres (Triamino-KCC-1) was successfully fabricated, for the first time, via anchoring 3-[2-(2 Aminoethylamino) ethylamino] propyltrimethoxysilane by a facile and effective post-grafting approach. Triamino-KCC-1 with fibrous silica nanosphere morphology showed large pore volume (1.15 m3 g–1) and surface area (∼536 m2 g−1) containing the micro-mesostructured silica fibers. The adsorption behaviors of hexavalent chromium (CrVI) from aqueous media on the Triamino-KCC-1 adsorbent were monitored as a function of initial pH solution, adsorbent dose, initial CrVI concentration, and contact time. The Triamino-KCC-1, as a novel functionalized fibrous silica adsorbent, had high adsorption efficiency at acidic pH and the adsorption rate was fast. The adsorption data for Triamino-KCC-1 was consistent with the Langmuir isotherm model with a calculated maximum uptake capacity of ∼316 mg g−1, which was in reasonable agreement with experimental adsorption capacity (∼317 mg g−1). According to the results obtained by applying isotherm and kinetic parameters, we can conclude that the most active sites of Triamino-KCC-1 are easily accessible. The results obtained in the present study indicate that it is of great practical and research interest to develop functionalized fibrous silica-based adsorbents for effective heavy metals removal.