Hierarchical Silica Research Articles

Electricity Harvesting from Water Evaporation on Hierarchical Pore Gradient Silica Aerogel-Based Generators.

In this study, the electric energy harvesting capability of the hierarchical pore gradient silica aerogel (HPSA) is demonstrated due to its unique porous structure and inherent hydroxyl groups on the surface. Taking advantage of the positively charged surface of unwashed HPSA credited by the preparation strategy, poly(4-styrene sulfonic acid) (PSS) can be spontaneously adsorbed onto unwashed HPSA and shows gradient distribution due to the pore-gradient structure of HPSA. By virtue of the gradient distribution and the stronger ionization of PSS, PSS-modified HPSA (PSS-HPSA) shows enhanced electricity generation performance from natural water evaporation with an average output voltage of 0.77 V on an individual device. The water evaporation-induced electricity property of PSS-HPSA can be maintained in the presence of a low concentration of salt. The desirable salt resistance capability benefits from the unique 3D hierarchical porous structure of HPSA which ensures rapid water replenishment so as to effectively avoid the salt accumulation. The HPSA-based devices with the advantages of unique porous structure, easy functionalization, good physicochemical stability, good salt resistance capability, and eco-friendliness show great potential as water evaporation-induced electricity generators.

Hierarchical Silica Composites for Enhanced Water Adsorption at Low Humidity.

To combat water scarcity in remote areas around the world, adsorption-based atmospheric water harvesting (AWH) has been proposed as a technology that can be used alongside existing water production capabilities. However, commonly used adsorbents either have low water adsorption loadings or are difficult to regenerate. In this work, we developed two novel hierarchical silica-salt composites that both exhibit high water adsorption loadings under dry and humid conditions. The total water vapor loading, kinetics, and heats of water adsorption for both silica-salt composites were investigated. As hierarchical silicas have tunable pores and large pore volumes, these materials serve as effective host matrixes for the hygroscopic salt LiCl. Our results suggest that hierarchical pores play a significant role in water adsorption: micropores and some smaller mesopores act as "storage" sites for hygroscopic salt, whereas larger mesopores and macropores increase the accessibility of water vapor into the silica. Using this mix of pores, we achieved greater than 0.4 g H2O/g composite at 10% RH and 27 °C. Additionally, we found that the salt-impregnated silica and bare silica had the same heat of adsorption: 80-90 kJ/mol. The results suggest that the H-bond interactions are similar for both systems and that the primary mechanism at play here is water cluster adsorption/desorption. Despite the similar energies, the LiCl-containing materials exhibited considerably slower kinetics than bare silica materials. Of equal importance to the adsorption capacity and kinetics of these composites is their mechanical stability. To assess their mechanical stability, high-energy ball milling of silica was conducted to create more uniform particle sizes. However, reduced particle sizes came at a cost─the BET surface areas and pore volumes were drastically decreased after more than 1 h of ball milling. Findings from this study suggest that short-term ball milling may be a viable large-scale option to reduce particle size in silica materials without sacrificing significant performance.

Continuous flow synthesis of hierarchical low silica X zeolite

Zeolites, renowned for their versatile applications in catalysis, adsorption, and ion exchange, have long been synthesized using conventional batch processes. However, the inherent limitations of these methods, such as resource-intensive conditions and inconsistent product quality, underscore the need for a sustainable and efficient approach. In this study, a continuous flow synthesis process was established for the synthesis of industrially important low silica X (LSX) zeolite using a tubular reactor. The synthesis gel was subjected to aging for 5 days at room temperature to facilitate nucleation and crystal growth combined with the fast-heating rate in a tubular reactor at 363 K & 1.1 atm., which in turn produces LSX after 40 min. The synthesized product was confirmed by the XRD, FE-SEM, EDS, XRF, TEM, and N2 adsorption-desorption; the data was compared with the LSX sample synthesized by batch process. The result implies that LSX prepared by continuous flow has a pure phase of LSX with the hierarchical structure, which provides better adsorption capacity of CO2 at 298 K up to 20 bar. Due to continuous flow synthesis, the crystallization time was reduced and faster kinetics which may be helpful for scale-up the process for LSX synthesis.

Robust and renewable hierarchical silica nanowires grown on a stainless steel mesh for oil/water separation

Porous filters with selective wetting properties offer a more effective route for separating oil and water than traditional industrial processes. However, developing durable structures for emulsion purification remains a challenge. Herein, we present a filter comprising a stainless steel mesh decorated with silica nanowires, which is highly resistant to fouling (almost 0° water contact angle and 166° underwater oil contact angle) and demonstrates excellent separation efficiency and reusability. The nanowire filter is particularly suited for separating n-hexane/water emulsions, where the oil phase could be completely separated by the filter. In addition, it demonstrates remarkable resistance to acid (pH 2 for 10 days), salt solution (37 days), butane flame, and abrasion, indicating its applicability in harsh environmental conditions. By combining the advantages of low-cost production, excellent separation, and enhanced durability, this nanowire filter holds significant potential for oil/water separation applications.

Direct CO2 capture from simulated and Ambient Air over aminosilane-modified hierarchical silica

Aminosilane-modified Hierarchical silica, HSA and HST-based adsorbents were synthesized by aminosilanization using Hierarchical silica (HS) with 3-aminopropyltriethoxysilane (APS) and N1-(3-trimethoxysilylpropyl)diethylenetriamine (TMPTA), respectively, and characterized to establish their physicochemical, structural, morphological, and porosity properties. Their CO2 adsorption performance was evaluated under direct air capture (DAC) conditions: 1) simulated air with CO2 concentration of 400 ppm in helium (He) at 30 °C and 2) indoor air with CO2 concentration ≥400 ppm at 30 °C, where HSA and HST modified with 70 wt% of respective aminosilanes outperformed others. The modified HS adsorbents showed an increase in kinetics, CO2 uptake under dry and humid conditions, stable cyclic adsorption-desorption performance, moderate enthalpy of desorption indicating a dominant chemisorption mechanism. Under dry and humid simulated air conditions (400 ppm CO2 in He), HSA-70 displayed a CO2 uptake of 0.82 mmol/g and 1.70 mmol/g, respectively, while HST-70 exhibited enhanced CO2 uptake of 1.54 mmol/g and 2.08 mmol/g, respectively. Cyclic stability of HSA-70 and HST-70 was confirmed through five thermal swing adsorption (TSA) cycles. In addition to this, their use for indoor air CO2 capture was also explored through ten short TSA cycles. Developed HSA-70 and HST-70 adsorbents exhibited more selectivity for CO2 over water, demonstrating their usage in practical direct air CO2 capture application.

Effect of molar concentration and drying methodologies on monodispersed silica sol for synthesis of silica aerogels with temperature-resistant characteristics

A variety of hierarchical nanoporous silica aerogels with diversified particle distributions were synthesized from well-dispersed silica sols by a traditional sol–gel method. Among the six particle sizes of aerogels, the silica aerogel with 0.4 M TEOS/MTMS surface modification and supercritical drying attains 11.61 ± 2.96 nm constituent part with well slender size particle dissemination, high-temperature confrontation and low thermal conductivity. In association with the outmoded two-step acid-base dilution of silica sols, the well-diffused form of silica sols with surface alteration also provides a low thermal conductivity of 0.01865 W.m−1 K−1 with greater thermal resistance. In addition, the drying shrinkage can be minimized with surface modification by properly silylation with TMCS. The concentrations of well-diffused silica sol were adjusted to achieve higher surface area, low density, large pore size and structure, and temperature resilience with the help of controlling the sol–gel reaction. The resilient skeleton structure developed from the assembly of tiny particles can efficiently restrict the glutinous heat dissipation between aerogel networks without collapsing a porous network up to a higher temperature of 900 °C. However, this network retains a similar pattern up to 1000 °C with only 32 % volume contraction after 2hr of heat treatments. At an elevated temperature of 1100–1200 °C, the viscid heat flow between nanoparticles and the porous network cannot be meritoriously suppressed and starts to collapse after a shorter duration. The enormous results of silica aerogels will help design suitable thermal insulation with higher resilience and low thermal conductivity.

Surface reconstruction, modification and functionalization of natural diatomites for miniaturization of shaped heterogeneous catalysts

Since the discovery of mesoporous silica in 1990s, there have been numerous mesoporous silica-based nanomaterials developed for catalytic applications, aiming at enhanced catalytic activity and stability. Recently, there have also been considerable interests in endowing them with hierarchical porosities to overcome the diffusional limitation for those with long unimodal channels. Present processes of making mesoporous silica largely rely on chemical sources which are relatively expensive and impose environmental concerns on their processes. In this regard, it is desirable to develop hierarchical silica supports from natural minerals. Herein, we present a series of work on surface reconstruction, modification, and functionalization to produce diatomite-based catalysts with original morphology and macro-meso-micro porosities and to test their suitability as catalyst supports for both liquid- and gas-phase reactions. Two wet-chemical routes were developed to introduce mesoporosity to both amorphous and crystalline diatomites. Importantly, we have used computational modeling to affirm that the diatomite morphology can improve catalytic performance based on fluid dynamics simulations. Thus, one could obtain this type of catalysts from numerous natural diatoms that have inherently intricate morphologies and shapes in micrometer scale. In principle, such catalytic nanocomposites acting as miniaturized industrial catalysts could be employed in microfluidic reactors for process intensification.

Novel 3D@2D/2D HHSS@BiOBr/Znln2S4 S-scheme photocatalyst for efficient adsorption-photocatalytic-photosensitization synergistic degradation of organics

Constructing high-performance multifunctional visible-light-driven photocatalysts to remediate organic contaminants from wastewater is of great challenge. Herein, we report a novel 3D@2D/2D hierarchical heterogeneous structured HHSS@BiOBr/Znln2S4 (HBZ) with abundant sulfur vacancies nanocomposite. This unique photocatalyst was fabricated by in situ growth of BiOBr nanosheets on the surface of hierarchical hollow silica spheres (HHSS), followed by epitaxial growth of Znln2S4 nanosheets for effective degradation of TCH and RhB. The optimal sample HBZ-6 (60 wt% Znln2S4) exhibited adsorption-photocatalytic synergistic degradation rate up to 92.36% after 30 min visible light irradiation, which was 2.31 times higher than that of bare BiOBr. It is benefit from the strong adsorption capacity of HHSS and effective carrier separation of 2D/2D S-scheme BiOBr/Znln2S4 in the HBZ-6 photocatalyst. Furthermore, it was surprising to discover that the coloured dye RhB was 100% photodegraded by HBZ-6 photocatalyst in 2 min under visible light, which is much faster than that of TCH with low visible light absorption. This excellent degradation efficiency is attributed to adsorption-photocatalytic-photosensitization synergistic between RhB and HBZ-6, leading to the ultrafast dye-sensitized-assisted electron transfer process. This work provides progressive tactics to design 3D@2D/2D defect heterogeneous structures which can greatly promote the future development of catalytic systems for wider application.

LaVO4: Eu3+ nano-islands onto silica for achieving fluorescence enhancement and their detection of Fe3+ ions and anti-counterfeiting applications

Rare earth (RE) composite fluorescent materials are favored by researchers in the field of anti-counterfeiting and ion sensing due to their fascinating optical properties. Ultra-small RE fluorescent nanoparticles are anchored on inorganic carriers by a simple preparation method to improve luminous intensity and hydrophilicity, which has not been explored yet. Herein, LaVO4: Eu3+ nano-islands anchored on silica with high fluorescence intensity and easy formation of stable colloidal solution is designed. Through a simple and mild hydrothermal approach, ultra-small LaVO4: Eu3+ nano-islands are highly dispersed on the surface of hierarchical hollow silica sphere (HHSS) to expose more luminescent centers. Remarkably, the stable HHSS@LaVO4: Eu3+ colloidal solution displayed highly sensitive and selective sensor for Fe3+ ions. The “island-sea synergy” structure formed by the LaVO4: Eu3+ nano-islands and the surrounding silica surface makes HHSS@LaVO4: Eu3+ to be an outstanding sensor for the effective detection of iron ions in water. In addition, HHSS@LaVO4: Eu3+ phosphor exhibit unique properties for anti-counterfeiting and encryption applications. These findings provide a promising strategy for the carrierisation of RE luminescent materials to improve optical properties and enable broader applications.

Immobilization of Aspergillus sp. laccase on hierarchical silica MFI zeolite with embedded macropores

Laccase from Aspergillus sp. (LC) was immobilized on functionalized silica hierarchical (microporous-macroporous) MFI zeolite (ZMFI). The obtained immobilized biocatalyst (LC#ZMFI) was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (ATR-FTIR), N2 adsorption/desorption isotherms, solid-state NMR spectroscopy and thermogravimetric analysis (TGA) confirming the chemical anchoring of the enzyme to the zeolitic support. The optimal pH, kinetic parameters (KM and Vmax), specific activity, as well as both storage and operational stability of LC#ZMFI were determined. The LC#ZMFI KM and Vmax values amount to 10.3 µM and 0.74 µmol·mg−1 min−1, respectively. The dependence of specific activity on the pH for free and immobilized LC was investigated in the pH range of 2–7, The highest specific activity was obtained at pH = 3 for both free LC and LC#ZMFI. LC#ZMFI retained up to 50 % and 30 % of its original activity after storage of 21 and 30 days, respectively. Immobilization of laccase on hierarchical silica MFI zeolite allows to carry out the reaction under acidic pH values without affecting the support structure.

Investigation of Electrochemical Assisted Deposition of Sol-Gel Silica Films for Long-Lasting Superhydrophobicity

Current methods for the protection of metal surfaces utilize harsh chemical processes, such as organic paint or electro-plating, which are not environment-friendly and require extensive waste treatments. In this study, a two-step approach consisting of electrochemical assisted deposition (EAD) of an aqueous silane solution and a dip coating of a low surface energy silane for obtaining a superhydrophobic self-cleaning surface for the enhanced protection of copper substrate is presented. A porous and hierarchical micro-nanostructured silica basecoat (sol-gel) was first formed by EAD of a methyltriethoxysilane (MTES) precursor solution on a copper substrate. Then, a superhydrophobic top-coat (E-MTES/PFOTS) was prepared with 1H,1H,2H,2H-Perfluorooctyltriethoxysilane (PFOTS) for low surface energy. The superhydrophobic coating exhibited anti-stain properties against milk, cola, and oil, with contact angles of 151°, 151.5°, and 129°, respectively. The EAD deposition potential and duration were effective in controlling the microscopic morphology, surface roughness, and coating thickness. The E-MTES/PFOTS coatings exhibited chemical stability against acids, bases, and abrasion resistance by sandpaper. The proposed 2-layer coating system exhibited strong chemical bonding at the two interfaces and provided a brush-like surface morphology with long-lasting superhydrophobicity. The developed method would provide an environment-friendly and expedient process for uniform protective coatings on complex surfaces.

Direct Air Capture of CO2 over Amine-Modified Hierarchical Silica

The current study reports the utilization of tetraethylenepentamine (TEPA)-modified hierarchical silica particles having bimodal meso/macroporosity for CO2 capture under simulated direct air capture (DAC) conditions (400 ppm CO2 in He). Results infer a typical relation between TEPA loading and CO2 capture, where TEPA-impregnated HS (HS-TEPA-70) exhibits exceptionally high CO2 uptake (5.20 mmol/g), shorter adsorption half time (110 min), and excellent amine efficiency (0.32 mmol of CO2/mmol of N) with moderate CO2/N2 selectivity at 30 °C under DAC conditions. HS-TEPA-70 also showed appreciable CO2 adsorption performance (5.88 mmol/g) under humid conditions (50 ± 3% RH) with 400 ppm CO2 in He at 30 °C. TEPA-impregnated HS even displays better thermal stability up to 10 consecutive adsorption–desorption cycles with minimal amine leaching and moderate CO2 regeneration energy. Moreover, the pelletized form of HS-TEPA-70 also demonstrates better CO2 adsorption performance (3.34 mmol/g), which makes it a promising candidate for CO2 capture from ambient air by temperature swing adsorption.

Copper Oxide Nanoparticles over Hierarchical Silica Monoliths for Continuous-Flow Selective Alcoholysis of Styrene Oxide

A simple and reproducible approach for the synthesis of Cu-based heterogeneous catalysts, named flow chemisorption hydrolysis (flow-CH), is reported. The approach, derived from the CH method, allows size-controlled CuO nanoparticles (mean diameter 2.9 nm) to be obtained, that are highly and homogeneously dispersed into hierarchically meso-/macroporous silica monoliths. The Cu-based monolithic catalysts (CuO@SiO2-MN, 8.4 wt.% Cu) were studied in the styrene oxide ring opening reaction at 60 °C in the presence of isopropanol, under continuous flow-through conditions. A remarkable activity with a steady-state conversion of 97% for 13 h and 100% selectivity towards the corresponding β-alkoxyalcohol was observed. The performances of CuO@SiO2-MN were higher than those obtained in batch conditions with the previously reported CuO/SiO2 catalysts and with the ground CuO@SiO2-MN monolith in terms of productivity and selectivity. Moreover, a negligible Cu leaching (<0.6 wt.%) in reaction medium was observed. After 13 h CuO@SiO2-MN catalysts could be regenerated by a mild calcination (220 °C) permitting reuse.

Aminosilane-Modified Ordered Hierarchical Nanostructured Silica for Highly-Selective Carbon Dioxide Capture at Low Pressure

Ordered hierarchical nanostructured silica (OHNS) adsorbents were prepared, and their surface was controllably modified by aminosilanization using two different aminosilanes, one bearing one primary amine unit per molecule (4-aminobutyltriethoxysilane, ABTS) and the other bearing both a primary and a secondary amine (N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, AAMS). Following physicochemical, structural, morphological, and porosity characterization, the CO2 adsorption performance was evaluated at low pressures (up to 100 mbar) and at different temperatures (25, 45, and 60 °C), including determination of CO2 adsorption–desorption, kinetics, CO2/N2 selectivity, regeneration/cycling, heat of adsorption, and CO2 adsorption under humid conditions. The unique hierarchical silica framework together with the aminosilanization scheme applied resulted in enhanced kinetics and CO2 uptake, the latter being increased with temperature, thus revealing a dominant chemisorption mechanism, which was further evidenced by the increase in the enthalpy of adsorption of the modified materials compared to the pristine OHNS. Among the tested adsorbents, at 100 mbar and 25 °C, the OHNS modified by AAMS yielded the highest CO2 uptake under dry (1.3 mmol/g) and wet (1.9 mmol/g) conditions. Notably, at very low pressure (1 mbar), the CO2 capacity of OHNS-AAMS reached >40% of the material’s total uptake at 1 bar. Compared to the unmodified OHNS, the CO2 capacity of the OHNS-AAMS and OHNS-ABTS increased by approximately 21- and 16-fold, respectively, at 1 mbar and 25 °C. At even lower pressure (0.4 mbar), a capacity of 0.55 mmol/g was evidenced for OHNS-AAMS in dry CO2. A very high CO2/N2 selectivity of the AAMS-modified analogue at low pressure was also obtained, i.e., 13,854 at 50 mbar, confirming the significant increase in CO2-philicity via aminosilanization with aminosilanes bearing combined primary and secondary amine groups. Furthermore, the water affinity of the aminosilane-modified OHNS adsorbents was found to decrease, which is beneficial for capture from humid mixtures. Cyclic stability was confirmed by performing 10 thermal pressure swing adsorption (TPSA) cycles up to 100 mbar. The hierarchical nanostructured silica-based framework and the functionalization scheme presented here render these robust systems promising for selective CO2 capture at low pressures in industrial applications and direct air capture.

Hierarchical Macro-Mesoporous Silica Monolithic Tablets as a Novel Dose-Structure-Dependent Delivery System for the Release of Confined Dexketoprofen.

This study reports the application of hierarchical porous monoliths as carriers for controlled and dose-adjustable release of model pharmaceutical (dexketoprofen, DEX). The synthesis and detailed characterization of the hierarchical porous scaffolds are provided before and after the adsorption of three doses of DEX─a widely used nonsteroidal anti-inflammatory drug. The drug incorporated in the mesopores of silica was stabilized in an amorphous state, while the presence of macropores provided sufficient space for drug crystallization as we demonstrated via a combination of powder X-ray diffraction, differential scanning calorimetry, and imaging techniques (scanning electron microscopy and EDX analysis). Drug release from silica matrices was tested, and a mechanistic model of this release based on the Fick diffusion equation was proposed. The hierarchical structure of the carrier, due to the presence of micrometric macropores and nanometric mesopores, turned out to be critical for the control of the drug phase and drug release from the monoliths. It was found that at low drug content, the presence of an amorphous component in the pores promoted the rapid release of the drug, while at higher drug contents, the presence of macropores favored the crystallization of DEX, which naturally slowed down its release. Both the hierarchical porous structure and the control of the drug phase (amorphous and/or crystalline) were proven important for adjustable (fast or prolonged) release kinetics, desirable for effective pharmacotherapy and patient compliance. Therefore, the developed materials may serve as a versatile formulation platform for the smart manipulation of drug release kinetics.

Tailorable Formation of Hierarchical Structure Silica (HMS) and Its Application in Hydrogen Production

Relentless endeavors have been committed to seeking simple structure-directing agents for synthesizing hierarchical mesoporous silica (HMS) materials but remaining challenges. In this contribution, we offered an improved one-pot hydrothermal route to prepare HMS materials using a single non-ionic triblock copolymer (F127) structure-directing agent under a mild polycarboxylic (citric acid) mediated condition. Via studies of key synthetic parameters including acid concentration, crystallization temperature and aging time, it was found that citric acid medium presents an important bridging effect under the optimal concentration from 0.018 M (pH = 2.57) to 1.82 M (pH = 1.09), contributing to the self-assemblage of partially protonated non-ionic triblock copolymer and tetraethyl orthosilicate (TEOS) into a high-quality multistage structure of silica materials. The specific surface area (SSA) of HMS shows a volcanic trend and is closely associated with the concentration of citric acid while the highest SSA of 739.9 m2/g can be achieved at the citric concentration of 0.28 M. Moreover, the as-synthesized HMS-CTA supported Ni/CeO2 catalysts indicate an excellent production of hydrogen through dry reforming of methane (DRM) reaction over 172 h stability. The improved, facile synthesis strategy under polycarboxylic medium displays an expanded perspective for synthesizing other mesoporous materials in a wide range of applications such as catalytic material carriers and drug inhibitors.

Excellent chemoselective hydrogenation of nitroaromatics and unsaturated aldehyde at the confined silver nanospace

Catalytic reduction of nitroarenes and unsaturated aldehydes to corresponding hydrogenated products is an environment-friendly technology to prepare industrially important intermediates. however, high chemoselectivity still remains a big challenge when a nitroarene or unsaturated aldehyde molecule with two or more reducible groups. Herein, we construct a novel confined catalyst by encapsulating Ag NPs into the nanospace of hierarchical hollow silica (SiO2-Ag@void@SiO2), enabling the excellent chemoselective hydrogenation (>99%) of 2-nitrochlorobenzene and cinnamyl aldehyde into corresponding amino groups (-NH2) and hydroxyl groups (-OH) without hydrogenating other functional groups (-Cl and CC). The unique hydrogenation performance is identified to be associated with the confinement effect and highly dispersed Ag NPs because hydrogenation reaction takes place within the confined silver nanospace. Therefore, our study provides a guide to construct highly active catalysts for chemoselective catalysis.

Composite film with hollow hierarchical silica/perfluoropolyether filler and surface etching for performance enhanced triboelectric nanogenerators

Triboelectric nanogenerators (TENGs), capable of harvesting distributed energy from the environment, have provided a viable solution for self-powered wearable electronics. However, their low power density and susceptibility to contamination still severely limit their practical application. Herein, we reported a “two-step” strategy to implement a waterproof self-powered wearable electronic device based on TENG. Firstly, Perfluoropolyether (PF) and hollow hierarchical silica (H-SiO2) as fillers significantly improve the dielectric properties of polydimethylsiloxane (PDMS) composite films (PFS films) through polarization effect. Then the nano bumps of 10–30 nm are created on the surface of the films by surface etching, the bumps can increase the contact area of TENG. The voltage of TENG is improved from ∼ 67 V to ∼ 910 V and the current is improved from ∼ 1 μA to ∼ 25 μA. What’s more, the investigation of the surface structure of the PFS composite films by Atomic Force Microscope (AFM) revealed that the synergistic combination of multiple nanoscales (10–30 nm, 60–80 nm, 300–500 nm) is more favorable to achieve high performance of TENG. The surface structure composed of multiple nanoscales endows PFS with excellent superhydrophobicity. The PFS films remained fine performance after 40,000 drops of water and 90 days. This work achieves high performance and water resistance of TENG, demonstrating great potential in the field of self-powered wearable electronic devices.

Design of hierarchical self-assembly 2D silica and their derivative catalysts with accessible open transport channels for boosting oxidative-adsorptive desulfurization in fuel oil

The design and synthesis of hierarchical self-assembled 2D-channel silica (2D-CS) with mesoscopicshape control and developing of their application in catalysis has remained a challenge. Herein, we fabricated a series of 2D-CSx materials through the hierarchical self-assembly of curved lamellar micelles along with their derivative 2D channel catalysts (2D-CSx-NH2-HPW) by grafting amino groups and immobilizing phosphotungstic acid. These catalysts exhibit highly effective oxidative-adsorptive desulfurization (OADS) performance owing to their accessible open-transport channels. A novel theory that the stacking of curved lamellar micelles is similar to that of wrinkled-papers was proposed to explain the hierarchical self-assembly mechanism of the 2D-CS materials, which follows the “short-range order, long-range disorder” rule. Systematic characterizations and experiments indicated that the size and specific surface area of 2D-channel catalysts jointly determine their OADS performance. Most importantly, the 2D-channel catalysts show the highest removal efficiency of DBT when compared with 0D and 1D materials, which was ascribed to their facilitation of molecular diffusion owing to their accessible open-transport channels. The optimal 2D-channel catalysts (2D-CS4-NH2-HPW) exhibited excellent desulfurization performance despite omitting the extraction step, and the removal efficiency of DBT reached 99.72% in 5 min at 60 °C, much faster than previously reported mesoporous-catalyst-supported heteropoly acids. In addition, the OADS activity of typical sulfur compounds in the presence of the 2D-CSx-NH2-HPW catalyst was investigated, and the sulfur removal efficiency was found to decreases in the following order: DBT > 4,6-DMDBT > BT > n-DDM. The 2D-channel catalyst also exhibits excellent recyclability without significant loss of OADS activity after 10 cycles of reactions. This work provides a strategy for constructing 2D-channel catalysts for efficient desulfurization, demonstrating the potential of 2D-channel materials in catalytic applications.

Investigating the Morphology and Mechanics of Biogenic Hierarchical Materials at and below Micrometer Scale.

Investigating and understanding the intrinsic material properties of biogenic materials, which have evolved over millions of years into admirable structures with difficult to mimic hierarchical levels, holds the potential of replacing trial-and-error-based materials optimization in our efforts to make synthetic materials of similarly advanced complexity and properties. An excellent example is biogenic silica which is found in the exoskeleton of unicellular photosynthetic algae termed diatoms. Because of the complex micro- and nanostructures found in their exoskeleton, determining the intrinsic mechanical properties of biosilica in diatoms has only partly been accomplished. Here, a general method is presented in which a combination of in situ deformation tests inside an SEM with a realistic 3D model of the frustule of diatom Craspedostauros sp. (C. sp.) obtained by electron tomography, alongside finite element method (FEM) simulations, enables quantification of the Young’s modulus (E = 2.3 ± 0.1 GPa) of this biogenic hierarchical silica. The workflow presented can be readily extended to other diatom species, biominerals, or even synthetic hierarchical materials.