Hierarchical Mesopores Research Articles

Morphology adjustment of ZSM-5 nanocrystal agglomerates and achievement of improved activity in LDPE catalytic cracking reaction

Abstract The cuplike ZSM-5 nanocrystal agglomerates were directly synthesized following an organic template-free strategy with the assistance of a preformed MFI precursor (the seed solution) and a nonionic-type polyacrylamide (PAM), which play the roles of nucleation promotion and crystal growth restriction, respectively. The morphological adjustment approach, hierarchical mesopore structure evolution, and the derived acidic properties of the resulting ZSM-5 nanocrystal agglomerates were systematically investigated. The cuplike agglomerates possessing a thin-wall structure which is composed of monolayer ZSM-5 nanocrystals can be synthesized by simply prolonging the high-temperature (448 K) crystallization. Due to the morphological characteristics, the diffusion pathway in the resulting cuplike ZSM-5 nanocrystal agglomerates (CZNA) is perpendicular to the cup wall and the length is identical to the wall thickness, around 200 nm. As for the formation of the cuplike morphology, the MFI composition building units (CBU) in the center nanocrystals continuously dissociate, migrate, rearrange, and assemble onto the nanocrystals close to the external surface of the preformed agglomerates, thereby forming a “shell-like” structure. After random collapse takes place on the “shell” through prolonging the high-temperature hydrothermal treatment, a cuplike morphology is obtained. As the consequence, the CZNA simultaneously possesses a high crystallinity and a highly open mesostructure, especially as well as the extremely short diffusion pathway. Because of these advantages, CZNA exhibits very high catalytic activity in the Low Density Polyethylene (LDPE) catalytic cracking reaction.

Facile synthesis of hierarchical mesopore-rich activated carbon with excellent capacitive performance

Mesoporous carbons attract increasing attention owing to their potential applications in supercapacitors. So far, controlled synthesis of mesoporous carbons with a narrow pore size distribution relies largely on the complicated template methods. To avoid the use of templates, a surfactant–free emulsion polymerization method is presented for the fabrication of a melamine–modified phenolic resin microrod (MPRR) assembled by micron–sized spherical cells and thin walls. In addition, one–step KOH activation strategy is adopted to synthesize hierarchical mesoporous activated carbon with 2–10 nm narrow mesopores by using MPRR as carbon precursors. The as–prepared mesoporous activated carbon has a high specific surface area of about 2758 m2 g−1 and a mesopore volume of 0.54 cm3 g−1 (calculated by density functional theory), comprising ∼43.5% of total pore volume (∼1.43 cm3 g−1). Hierarchical mesopores can significantly accelerate ion transfer and increase micropore accessibility, which endow the carbon with high specific capacitance equal to 409 F g−1 at 0.1 A g−1 and 268 F g−1 at 100 A g−1 in 6 M KOH electrolyte, with a high capacitance retention of 66%. Moreover, the assembled symmetric supercapacitor also exhibits good cycling stability in KOH electrolyte and delivers high power density equal to 12080 W kg−1 when energy density is 5.02 Wh kg−1. This finding provides an insight into directional tailoring of mesoporous structures of phenolic resin–based carbon materials at the molecular level for high–performance supercapacitors.

Three-Dimensional Graphene/Ag Aerogel for Durable and Stable Li Metal Anodes in Carbonate-Based Electrolytes.

The use of Li metal as the anode for Li-based batteries has attracted considerable attention due to its ultrahigh energy density. However, the formation of Li dendrites, uneven deposition, and huge volume changes hinder its reliable implementation. These issues become much more severe in commercial carbonate-based electrolytes than in ether-based electrolytes. Herein, a rationally designed three-dimensional graphene/Ag aerogel (3D G-Ag aerogel) is proposed for Li metal anodes with long cycle life in carbonate-based electrolytes. The modified lithiophilic nature of G-Ag aerogel, realized through decoration with Ag NPs, effectively decreases the energy barrier for Li nucleation, regulating uniform Li deposition behavior. Moreover, the highly flexible, conductive 3D porous architecture with hierarchical mesopores and macropores can readily accommodate deposited Li and ensures the integrity of the conductive network during cycling. Consequently, high coulombic efficiency (over 93.5 %) and a significantly long cycle life (1589 h) over 200 cycles, with a relatively high cycling capacity of 2.0 mAh cm-2 , can easily be achieved, even in a carbonate-based electrolyte. Considering the intrinsic high voltage windows of carbonate-based electrolytes, matching the G-Ag aerogel Li metal anode with a high-voltage cathode can be envisaged for the fabrication of high-energy-density Li secondary batteries.

Synthesis of surface-replicated ultra-thin silica hollow nanofibers using structurally different carbon nanofibers as templates

Ultra-thin silica hollow nanofibers were successfully synthesized using three kinds of well-defined carbon nanofibers (CNFs) with different surface structures as effective templates via pyrolysis of polycarbomethylsilane-coated CNFs. The prepared silica hollow nanofibers replicated the characteristic surface morphologies of the CNFs, such as herringbone, platelet, and tubular types with edge or basal planes. Especially, the unique HCNF template, with tiny fibril aggregates on the surface, was the most effective template material for synthesizing ultra-thin silica hollow nanofibers with uniform and hierarchical meso-pores and high surface areas (over than 680 m2/g). The chemical and physical properties of the silica nanofibers were evaluated with various analytical techniques, such as TGA, HR-TEM, FE-SEM, XRD, XPS, and N2 adsorption/desorption, and discussed in detail.

On the effect of mesoporosity of FAU Y zeolites in the liquid-phase catalysis

The porosity and acidity of three commercial FAU Y zeolites (including the original HY-2.6 and dealuminated HY-15/-30 zeolites) were studied comprehensively using nitrogen (N2) physisorption, and mercury (Hg) porosimetry, ammonia temperature-programmed desorption (NH3-TPD) and pyridine Fourier transform infrared (pyridine-IR) analyses. The combined N2 physisorption and Hg porosimetry is a useful tool to evaluate the hierarchical mesoporosity in the dealuminated samples, revealing that HY-15 and HY-30 possess >50% open mesoporosity in the mesopores range of 5–10 nm. The acidity of the dealuminated Y zeolites has been reduced significantly in comparison to that of the original HY-2.6, e.g. Bronsted acidity decreased by ca. 69 folds by dealuminating HY-2.6 to HY-30. Catalytic results of Fischer esterification of methanol with carboxylic acids and aldol condensation of benzaldehyde with 1-heptanal have evidenced that the critical role of mesoporosity of the dealuminated Y zeolites in liquid-phase reactions. For example, in the esterification of lauric acid with methanol, HY-15 and HY-30 with hierarchical mesopores showed better catalytic activity (i.e. conversion of lauric acid: 7.9% and 24.5%, respectively) than HY-2.6 (4.0%). The analysis of the catalytic results along with the acidic property suggests that the acidity is less influential than the porosity of zeolite catalysts. Results from this study allow us to explain the origin of the high activity of zeolites with mesoporosity in the liquid-phase catalysis.

Electrochemical synthesis of Sm-Cu dendritic metal catalysts by Co-reduction of Sm(III) and Cu(II) in LiCl-KCl-SmCl3-CuCl2 melt

Herein, we report a feasible and rapid route for the preparation of Sm-Cu intermetallic compounds used as an effective metal catalyst. The electrochemical processes of the co-reduction of Sm(III) and Cu(II) ions on Mo electrode or copper-coated Mo electrode in molten LiCl-KCl-CuCl2-SmCl3 system at 873 K were explored. The electrochemical behaviors of Sm(III), Cu(II) ions and intermetallic compounds formation in the melt were investigated by cyclic voltammetry (CV), chronopotentiometry, square wave voltammetry (SWV) and open-circuit chronopotentiometry (OCP), respectively. Our studies showed that the reduction of Cu(II) ions to Cu(0) metal involves two electrochemical steps, Cu(II)/Cu(I) and Cu(I)/Cu(0). Subsequently, Sm-Cu intermetallic compounds (SmCu6, SmCu5 and SmCu) were synthesized by a potentiostatic electrolysis method. As the electrode potential becomes increasingly negative, the formation of Sm-Cu intermetallic compounds gradually changes from Cu-rich side phases (SmCu6) to Sm-rich side phases (SmCu) with Sm-Cu alloys formed as single-crystal intermetallics. The crystal structures of Sm-Cu intermetallic compounds were characterized by X-ray diffraction (XRD), selected-area electron diffraction (SAED) and high-resolution transmission electron microscopy (HRTEM). Moreover, the morphology and chemical state of the constituting elements were investigated by scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS) analyses and X-ray photoelectron spectroscopy (XPS). The dendritic formation of Sm-Cu intermetallic compounds was characterized through nitrogen adsorption-desorption isotherms analysis. The formed Sm-Cu alloys contain hierarchical mesopores with different identified types of mesoporosity. The surface areas of SmCu6, SmCu5 and SmCu calculated from Brunauer-Emmett-Teller (BET) equation were 2.798 m2/g, 3.801 m2/g, 1.688 m2/g, respectively.

Ultrasmall Plasmonic Nanoparticles Decorated Hierarchical Mesoporous TiO2 as an Efficient Photocatalyst for Photocatalytic Degradation of Textile Dyes.

Hierarchical mesoporous TiO2 was synthesized via a solvothermal technique. The sonochemical method was adopted to decorate plasmonic nanoparticles (NPs) (Ag, Au) on the pores of mesoporous TiO2. The crystallinity, structure, and morphology were determined to understand the physicochemical nature of the nanocomposites. The catalytic efficiency of the plasmonic nanocatalysts was tested for the azo dyes (congo red, methyl orange, acid orange 10, and remazol red) under solar and visible light irradiations. The generation of hydroxyl radicals was also studied using terephthalic acid as a probe molecule. An attempt was made to understand the influence of size, work function and Fermi level of the metal NPs toward the efficiency of the photocatalyst. The efficiency of the nanocomposites was found to be in the order of P25 < mesoporous TiO2 < mesoporous Ag–TiO2 < mesoporous Au–TiO2 nanospheres under both direct solar light and visible light irradiation. The results indicated that the adsorption of dye, anatase phase, and surface plasmon resonance of NPs favored the effective degradation of dyes in aqueous solution. Further, the efficiency of the catalyst was also tested for xanthene (rose bengal), rhodamine (rhodamine B, rhodamine 6G), and thiazine (methylene blue) dyes. Both TiO2 and NPs (Ag & Au) possess a huge potential as an eco-friendly photocatalyst for wastewater treatment.

Efficient CO2separation in mixed matrix membranes with a hierarchical pore carbon nanostructure

Mixed matrix membranes (MMMs) based on Pebax MH 1657 (Pebax) and “sea‐urchin” like hierarchical mesopore–micropore carbon nanotube nanopolyhedras (CNPs) are fabricated for CO2separation. The membranes have an efficient improvement in CO2permeability and CO2/CH4selectivity with the addition of CNPs. The improved gas‐separation performance was attributed to the hierarchical mesopore–micropore structure of nanopolyhedras in CNPs and the “sea‐urchin” like structure of CNPs. First, abundant mesopores (4.8 nm) with a large pore volume and a connected porous network structure in nanopolyhedras can provide convenient gas transmission pathways to improve the CO2permeability. Second, micropores (1.1 nm) in nanopolyhedras play a role of molecular sieves and the outstretched CNTs of the “sea‐urchin” like structure of CNPs can extend the gas‐delivery path, which will enhance the CO2/CH4selectivity. Therefore, the CO2permeability and CO2/CH4selectivity are significantly enhanced. The MMMs with 8 wt% CNP show the highest CO2permeability of 510.1 Barrer and CO2/CH4selectivity of 56.8, the CO2separation performance surpassed the 2008 Robeson upper bound line.

Hierarchical Mesoporous Organosilica-Silica Core-Shell Nanoparticles Capable of Controlled Fungicide Release.

A new class of hierarchically structured mesoporous silica core-shell nanoparticles (HSMSCSNs) with a periodic mesoporous organosilica (PMO) core and a mesoporous silica (MS) shell is reported. The applied one-pot, two-step strategy allows rational control over the core/shell chemical composition, topology, and pore/particle size, simply by adjusting the reaction conditions in the presence of cetyltrimethylammonium bromide (CTAB) as structure-directing agent under basic conditions. The spherical, ethylene- or methylene-bridged PMO cores feature hexagonal (p6mm) or cage-like cubic symmetry (Pm3‾ n) depending on the organosilica precursor. The hexagonal MS shell was obtained by n-hexane-induced controlled hydrolysis of TEOS followed by directional co-assembly/condensation of silicate/CTAB composites at the PMO cores. The HSMSCSNs feature a hierarchical pore structure with pore diameters of about 2.7 and 5.6 nm in the core and shell domains, respectively. The core sizes and shell thicknesses are adjustable in the ranges of 90-275 and 15-50 nm, respectively, and the surface areas (max. 1300 m2 g-1 ) and pore volumes (max. 1.83 cm3 g-1 ) are among the highest reported for core-shell nanoparticles. The adsorption and controlled release of the fungicide propiconazole by the HSMSCSNs showed a three-stage release profile.

Synthesis of Ag nanoparticles decoration on magnetic carbonized polydopamine nanospheres for effective catalytic reduction of Cr(VI)

More discrete and active Ag nanoparticles (Ag NPs) were fabricated by decorating them on the surface of magnetic nanoparticles encapsulated in carbonized polydopamine nanospheres (M/C-PDA/Ag) via in-situ solid-state decomposition process. The morphology, structure, surface compositions and textural properties of the M/C-PDA and M/C-PDA/Ag catalyst were characterized. The results revealed a dispersion of Ag NPs with average particle size of less than 50 nm on C-PDA nanospheres uniformly embedded with Fe3C NPs of only 3–5 nm in size. With the synergistic effect of Ag NPs, nitrogen doping, and hierarchical mesopores, M/C-PDA/Ag displayed a superior catalytic capability for catalytic reduction of toxic Cr(VI) to less-toxic Cr(III) by formic acid as a reductant. Moreover, M/C-PDA/Ag maintained good physicochemical structure and stable activity even after several cycles of reactions. According to the results, the simple synthetic strategy, good stability, highly catalytic activity, and easy magnetic separation property of M/C-PDA/Ag hybrid make it serve as a promising environmentally friendly catalyst for the elimination of Cr(VI).

Peanut shaped MnCo2O4 winded by multi-walled carbon nanotubes as an efficient cathode catalyst for Li-O2 batteries

Rechargeable Li-O2 batteries have great potential on achieving large-capacity electrochemical energy storage. However, the poor cyclic stability seriously limits its commercial application. In this paper, peanut shaped MnCo2O4 which winding by multi-walled carbon nanotubes (MCO/MWCNTs) were synthesized through a facile solvothermal method. As-prepared MCO/MWCNTs have a unique hierarchical mesoporous of three-level pore sizes and show good ORR and OER electrocatalytic activity. When MCO/MWCNTs served as cathode catalysts in Li-O2 batteries, the batteries exhibited long cycle life of 120 times at 100 mA g−1 with a limited capacity of 500 mAh g−1 and high discharge capacity up to 8849 mAh g−1 with a restrict voltage of 2 V at 100 mA g−1.

Morphology- and Porosity-Tunable Synthesis of 3D Nanoporous SiGe Alloy as a High-Performance Lithium-Ion Battery Anode.

The lithium storage performance of silicon (Si) can be enhanced by being alloyed with germanium (Ge) because of its good electronic and ionic conductivity. Here, we synthesized a three-dimensional nanoporous (3D-NP) SiGe alloy as a high-performance lithium-ion battery (LIB) anode using a dealloying method with a ternary AlSiGe ribbon serving as the precursor. The morphology and porosity of the as-synthesized SiGe alloy can be controlled effectively by adjusting the sacrificial Al content of the precursor. With an Al content of 80%, the 3D-NP SiGe presents uniformly coral-like structure with continuous ligaments and hierarchical micropores and mesopores, which leads to a high reversible capacity of 1158 mA h g-1 after 150 cycles at a current density of 1000 mA g-1 with excellent rate capacity. The strategy might provide guidelines for nanostructure optimization and mass production of energy storage materials.

Facile synthesis of 3D hierarchical mesoporous Fe-C-N catalysts as efficient electrocatalysts for oxygen reduction reaction

A salt crystal-templating synthesis route is proposed to synthesize a Fe-N-C catalyst with well-controlled mesoporous structure. In the presence of glucose, NaCl-template can efficiently tune the porous structure of catalyst and help to improve the oxygen reduction reaction (ORR) activity. The optimized catalyst possesses a hierarchical mesopore size distribution, a high Brunauer-Emmett-Teller surface area (up to 911.56 m2 g−1) and homogeneous distribution of abundant active sites. As a result, the obtained catalyst shows a desirable ORR activity in alkaline medium (half-wave potential of 0.84 V and kinetic mass activity at 0.8 V of 24.95 A g−1), high selectivity (electron transfer number >3.92), excellent long term durability (only 16 mV negative shift of half-wave potential after 5000 potential cycles in O2-saturated 0.1 M KOH) and good tolerance to methanol. The enhanced electrochemical performance enables the proposed catalyst to be the promising electrocatalyst candidate to commercial Pt/C towards ORR.

The flow-through silica as the matrix to immobilize gold nanoparticles for HPLC applications

ABSTRACTIn the present study, the flow-through silica, featured with hierarchical pores, i.e., tunable mesopores and penetrable macropores, was attempted as the chromatographic stationary phase matrix to immobilize gold nanoparticles (AuNPs). It was first modified by mercapto groups (named as SiO2-SH), and then by AuNPs (named as SiO2-S-Au). Thanks to the characteristic macropores, the column backpressure of SiO2-S-Au was comparable to SiO2-SH, which effectively overcame the difficulty of high column backpressure upon the nanoparticles were introduced to the chromatographic matrix. Both the reversed-phase and hydrophilic interaction liquid chromatographic performance were observed on these two columns but with different selectivities. Hydrophobic, hydrophilic, hydrogen bond and electrostatic interactions between the SiO2-S-Au stationary phase and analytes could contribute to the retention. The SiO2-S-Au column showed excellent aqueous compatibility by “Stop-flow” test with the relative standard deviations (RSD) of analyte’s k (capacity factor) values from 0.59% to 2.88%. The reproducibility of SiO2-S-Au was acceptable with RSDs of analyte’s k values in the range of 3.13%-5.03%. In addition, compared with the SiO2-SH column, the SiO2-S-Au column had better separation performance and selectivity. The results demonstrated that the flow-through silica was a promising matrix for nanoparticles with low backpressure and different selectivities.

In situ synthesis of sub-nanometer metal particles on hierarchically porous metal-organic frameworks via interfacial control for highly efficient catalysis.

In this work, we developed a strategy to in situ synthesize sub-nanometer metal particle/hierarchically mesoporous metal-organic framework (MOF) composites in emulsion. In this route, water droplets in the emulsion acted as both a solvent of the metal precursors and a template for the hierarchical mesopores of MOFs, and the surfactant was an emulsifier and a reductant for generating metal particles. Au/Zn-MOFs (MOFs formed by Zn2+ and methylimidazole), Ru/Zn-MOFs, Pd/Zn-MOFs, and Au/Cu-MOFs (MOFs formed by Cu2+ and methylimidazole) were prepared using this method, in which ultrafine metal particles (e.g. 0.8 nm) were immobilized uniformly on hierarchically mesoporous MOFs. Au/Zn-MOFs and Au/Cu-MOFs showed outstanding catalytic performances for the selective aerobic oxidation of cyclohexene to 2-cyclohexen-1-one in the absence of an initiator, and Ru/Zn-MOFs were very active and selective for the hydrogenation of diphenyl sulfoxide to diphenyl sulfide. In addition, the catalysts were also very stable in the reactions.

Preparation of 3D interconnected hierarchical porous N-doped carbon nanotubes

3D interconnected hierarchical porous N-doped carbon nanotubes (IHPNCs) were fabricated using palygorskite as template and polyaniline gel as carbon source, respectively. The prepared 3D IHPNCs show high specific surface area (517.02 m2 g−1), hierarchical porous structure (micropore (0.39 nm), mesopore (4.0 nm), macropore (≥50 nm)) and N-containing surface functionalities (pyridinic-N, pyrrolic-N, graphitic-N, N-oxides). Notably, the obtained 3D IHPNC electrodes exhibit a high specific capacitance of 389 F g−1 at 1 A g−1, excellent rate capability (290 F g−1 at 50 A g−1, 75% of capacitance retention) and cycling stability with 90% retention after 10000 cycles. Furthermore, the assembled 3D IHPNC symmetric supercapacitor delivers a high energy density of 8.7 Wh·kg−1 at a power density of 195 W kg−1 in 1.0 M Na2SO4 electrolyte, which is expected as a promising electrode candidate for supercapacitors.

Pore confinement effect of MoO3/Al2O3 catalyst for deep hydrodesulfurization

To investigate the pore confinement effect of MoO3/Al2O3 catalyst for deep hydrodesulfurization, a series of MoO3/γ-Al2O3 catalysts were prepared via impregnation method. All catalysts had almost the same physicochemical properties, such as the specific surface area, apparent morphology, microstructure, coordination of Al atom and acidity, and differed in the pore size. The control experiments results showed that enlarging the pore size from 3.6 to 8.8nm increased the desulfurization efficiency of 4,6-dimethyldibenzothiophene (4,6-DMDBT) from 62.6% to 95.0%, then decreased to 71.3%. The catalyst with a pore size of 5.9nm displayed the optimum hydrodesulfurization performance. The larger pores weaken the effect of polarization of Al3+ on the van der Waals interactions between the layers of active phase and result in more stacking of MoS2. The more stacked MoS2 contribute to more edge and corner active sites for the catalysts with the pore size of 5.9nm, which resulted that this catalyst exhibited the highest reaction rate and sulfidation degree of Mo species, lowest reduction temperature and largest amount of chemisorbed CO. The reaction and characterization results revealed that the smaller mesopores favored the accessibility of 4,6-DMDBT to the edge sites of MoS2 active phase, whereas the larger ones promoted the reactant molecules to the corner sites. Compared to the catalyst with mono-pore size, the catalyst with hierarchical mesopore structure had a higher hydrodesulfurization activity through the synergism of small and large pores. The larger pores enable 4,6-DMDBT to reach the active sites located in the small pores and promote the accessibility of the reactants to the corner sites of hexagonal shaped MoS2. This catalyst possessed a lower ratio of hydrodesulfurization products to direct desulfurization ones.

Synthesis, characterization and adsorptive denitrogenation performance of bimodal mesoporous Ti-HMS/KIL-2 composite: A comparative study on synthetic methodology

Novel titanosilicate composites with bimodal mesopores using molecular sieves Ti-HMS and Ti-KIL-2 as structural components were successfully synthesized by two-step and dual-template methods in a comparative study. The as-synthesized Ti-HMS/KIL-2 samples were characterized by a series of techniques including X-ray diffraction, UV–vis, N2 sorption and scanning electronic microscopy, and their performance was tested in adsorptive denitrogenation for model fuel containing pyridine or quinoline. Although Ti-HMS/KIL-2 composites were constructed following the different pathway of self-assembly, most of them obtained coexisting properties and structures of Ti-HMS and Ti-KIL-2, as well as the intact framework Ti in tetrahedral coordination. A key finding is that the mesopores size of Ti-KIL-2 component in the composite can be regulated via the introduction of Ti-HMS precursor or organic template dodecylamine. Especially, the composites of dual-template method presented hierarchical mesopores with obvious bimodal distribution. In addition to constructing the hierarchical structure, introduction of Ti-HMS into Ti-KIL-2 matrix improved the adsorptive denitrogenation performance, which was influenced by the synthetic strategy of Ti-HMS/KIL-2. The target adsorbates achieved the best match with the adjustable pores of Ti-HMS/KIL-2. Therefore, (0.6D)Ti-HMS/KIL-2 and (0.5T)Ti-HMS/KIL-2 as the optimized adsorbents obtained remarkable adsorption efficiency respectively for pyridine and quinoline. Essence of the adsorptive denitrogenation process was revealed via the adsorption isotherms and the adsorption thermodynamics. Finally, Ti-HMS/KIL-2 composites achieved the improvement in hydrothermal stability and recyclability during adsorption of pyridine and quinoline, and exhibited the potential of industrial application.

Adsorption of 4,6-dimethyldibenzothiophene and collidine over MoO3/γ-Al2O3 catalysts with different pore structures

Mesoporous γ-Al2O3 supports with different pore structures were prepared by the cation-anion double hydrolysis method. Based on these samples, MoO3/γ-Al2O3 catalysts were made via impregnation. The adsorptions of 4,6-dimethyldibenzothiophene (4,6-DMDBT) and collidine over the supports and catalysts were studied by FT-IR. The supports or catalysts with larger pores can adsorb more 4,6-DMDBT. The methyl groups on adsorbate molecules are very close to the sulfur atom, resulting in apparent steric hindrance. Increasing the pore size can promote the interaction between the adsorbates and supports or catalysts, enhancing the CC bond and weakening the CS bond of 4,6-DMDBT. 4,6-DMDBT molecules were coordinated with the unsaturated Mo atoms over the catalysts to form π-complexation adsorption. There was much difference between thiophene and 4,6-DMDBT adsorption. The adsorption of collidine over the catalysts also illustrated that there existed steric hindrance. Significantly, the catalyst with hierarchical mesopores was beneficial for the adsorbates with larger molecular dynamics diameter. Compared with the pore size, the specific surface area was not the key factor to affect the adsorptions of 4,6-DMDBT and collidine. The hydrodesulfurization reaction of 4,6-DMDBT illustrated that the catalysts with larger pore size or hierarchical pore structure presented higher desulfurization efficiency (above than 80%).

Flexible Hierarchical ZrO2 Nanoparticle-Embedded SiO2 Nanofibrous Membrane as a Versatile Tool for Efficient Removal of Phosphate.

Functional nanoparticles modified silica nanofibrous materials with good flexibility, a hierarchical mesoporous structure, and excellent durability would have broad applications in efficient removal of contaminants, yet have proven to be enormously challenging to construct. Herein, we reported a strategy for rational design and fabricating flexible, hierarchical mesoporous, and robust ZrO2 nanoparticle-embedded silica nanofibrous membranes (ZrO2/SiO2 NM) for phosphate removal by combining the chitosan dip-coating method with the electrospinning technique. Our approach allows ZrO2 nanoparticles to be in situ firmly and uniformly anchored onto SiO2 nanofibers to drastically enlarge the specific surface area and porosity of membranes. Therefore, the resultant ZrO2/SiO2 NM exhibited a prominent removal efficiency of 85% and excellent adsorption amount of 43.8 mg P g-1 membranes in 30 min toward phosphates. Furthermore, the removal performance toward different types of phosphates revealed that the resultant membranes also could be used to remove phosphates in detergent and fertilizer water samples. More importantly, the membranes with good flexibility could directly be taken out from solution after use without any post-treatment. Such a simple and intriguing approach for fabricating nanofibrous membranes may provide a new platform for constructing membranes with superb phosphate removal performance.