查看更多>>摘要：The hierarchical porous carbons (HPCs) are considered as promising supercapacitor electrode materials. However, most of them suffer from low volumetric capacitance values and rate performance. In the work, a kind of MgAl-layered double hydroxides (LDHs) templates is synthesized by co-precipitation and recrystallization strategy. It is found that the recrystallization can effectively decrease the overall dimensions and adjust the pore size of LDHs. By the use of LDHs as templates and polyethylene glycol-200 (PEG-200) as carbon precursors, a series of HPCs are synthesized. The HPCs basically copy the morphology of LDHs, and their electrochemical properties are influenced significantly by the recrystallization time of LDHs. With the 24h recrystallization of LDHs, the obtained HPC shows the highest compact density of 0.78 g cm(-3). It delivers the volumetric capacitance of 183 F cm(-3) and retains outstanding rate stability of 81.54% of initial capacitance when current density is increased to 50 times. Moreover, the volumetric energy density of 15.11 Wh L-1 (19.38 Wh kg(-1)) is achieved at the power density of 373.2 W L-1. This work provides a simple route to fabricate HPCs with high volumetric capacitance and rate performance.
查看更多>>摘要：Ultrathin ZnIn2S4 (ZIS) nanosheets were coated on g-C3N4 (CN) nanotubes to form CN@ZIS heterojunction as a high-performance photocatalyst for Cr(VI) reduction. Well-dispersed ZIS nanosheets on CN nanotubes favor the better utilization of light and the hierarchical pores promote the mass diffusion. Additionally, such in-situ growth of ZIS on CN nanotubes enables the formation of intimate interfacial contact between them and the obtained CN@ZIS displays a low recombination rate of photo-generated electron-hole pairs compared to the pristine CN and ZIS. Benefiting from these structural and compositional advantages, CN@ZIS exhibits a satisfactory photocatalytic Cr(VI) reduction efficiency and can reduce 30 mg/L Cr(VI) within 10 min (catalyst loading: 1 mg/mL) under visible-light irradiation. Such excellent performance makes CN@ZIS great potential in photocatalysis.
Bilgic, AliCimen, AyselKursunlu, Ahmed NuriKarapinar, Hacer Sibel...
11页
查看更多>>摘要：Sporopollenin is a natural substance found in plant walls and is highly resistant to external factors. In this paper, we designed an eco-friendly hybrid material, Sp-EDA-BODIPY , based on sporopollenin microcapsule and BODIPY to remove and detect metal ions. The fluorescent surface was fully characterized with various methods such as XRD, SEM, FT-IR, fluorescence spectroscopy. The fluorescent microcapsule sensor showed fluorometrically a remarkable quenching effect in the presence of Cu (II) ion, via the complexation mechanism that LOD it was calculated as 0.773 mu M. As a result of the competing ion experiments, Sp-EDA-BODIPY also has a high selective for Cu (II) ion toward another the studied metal ions. Otherwise, we also calculated the adsorption capacities and the maximum isotherm parameters and from the Freundlich, Langmuir, and DubininRadushkevich equations for the removal of Cu (II) with Sp-EDA-BODIPY fluorescent microcapsule. The maximum adsorption capacities of Cu (II) on Sp-EDA-BODIPY were calculated to be 28.65, 31.25, 34.02, and 37.74 mg/g at different temperatures (298, 308, 318, and 328 K), respectively. The adsorption experimental results were closer to Langmuir adsorption isotherm and pseudo-second-order models. Thermodynamic data showed that the adsorption process was endothermic, possible, and spontaneous.
查看更多>>摘要：The use of homogeneous and polluting halides as nucleophilic cocatalysts lowers the economy and benignity of the CO2-epoxide cycloaddition over heterogeneous Lewis-acid catalysts like metal-organic frameworks (MOFs). Creating net positive charge at frameworks is a reasonable strategy to heterogenize halide anions within MOFs, but it is still challenging to achieve high halide loading while keeping adequate porosity. In this article, we report a facile approach to ionic MOFs with high halide content and improved catalytic activity. The catalysts were prepared by reacting azide-tagged MIL-101 with alkyne-tagged organic bromide salts. The efficient azide-alkyne click reaction within the mesoporous MOF allows quantitative cationization of the linkers, and the resultant bifunctional ionic MOFs contain one halide ion per metal center to the benefit of the cooperative catalysis. Catalytic studies suggest that the effects of varying the cationic groups and halide anions in the confined ionic space are different from those observed for homogeneous organic halides. The highest catalytic activity was demonstrated for the MOF having the smallest cationic group (quaternized trimethyl ammonium) and the intermediately nucleophilic halide (Br-). The catalyst also outperforms the ionic MOF catalysts reported prior to this work.
查看更多>>摘要：This study aims to investigate the adsorptive removal of three TCAs; imipramine (IMI), nortriptyline (NOR) and desipramine (DES) using four polymeric networks based on triptycene (TRIP) and triphenylbenzene (TPB). For the first time, these polymeric networks have been used as a pure hydrocarbon (TRIP-HC and TPB-HC) and as their sulfonic acid derivatives (TRIP-SO3H and TPB-SO3H), for the decontamination of TCAs from wastewater. The effect of the initial TCAs concentration was investigated, and it was found that sulfonic acid modified polymers tolerated higher TCAs concentrations than their pure hydrocarbon-based counterparts. Furthermore, the adsorption kinetics and isotherms were studied, which indicated that the four polymers followed pseudosecond-order kinetics and Langmuir isotherm models, respectively. The adsorption capacities values for TRIP-SO3H and TPB-SO3H were between 196.0 and 384.6 mg g(-1), whilst for TRIP-HC and TPB-HC were between 133.3 and 175.4 mg g(-1). The effect of the presence of coexisting ions such as Cl-, NO3- and SO42- was also examined and the adsorption affinities of IMI, NOR and DES were slightly lowered using TRIP-SO3H and TPB-SO3H, on the other hand, a greater decrease was observed using TRIP-HC and TPB-HC. Furthermore, IMI in a tablet formulation was dissolved in tap water and TRIP-SO3H and TPB-SO3H were employed, and it was found they exhibited excellent adsorption efficiencies of 96.96 and 98.78%, respectively. Regeneration of these two polymers was tested by performing five adsorption-desorption cycles and TPB-SO3H showed better stability in comparison to TRIP-SO3H. Finally, a potential mechanistic pathway for the adsorption of theses pharmaceuticals by the polymers was also proposed.
Gomes, Diana P.Silva, Andreia F.Gomes, Ana C.Neves, Patricia...
14页
查看更多>>摘要：The confinement and catalytic behavior of Mo(CO)(6) species inside UiO-66 (zirconium and hafnium) metalorganic frameworks (MOFs) have been investigated by means of multitechnique characterization and catalytic olefin epoxidation. Mo(CO)(6) was encapsulated in nanocrystalline MOFs by solvothermal and vapor phase impregnation methods (STI and VPI, respectively), resulting in Mo loadings of 2.0-8.8 wt% (STI) or 15 wt% (VPI). Powder X-ray diffraction, SEM-EDS, N-2 adsorption, FT-IR and C-13{H-1} CP MAS NMR collectively confirmed immobilization within the pore spaces of the hosts, which maintained their bulk crystallinity and crystal morphologies. CO resonances in the C-13{H-1} CP MAS NMR spectra were assigned to hexacarbonyl guest molecules located in the larger pore spaces, such as the octahedral cavities (for STI and VPI samples), and in more restricted environments such as the tetrahedral cavities (for the VPI sample). FT-IR spectra displayed the characteristic pattern of nu(CO) stretching modes for an octahedral symmetry molecule slightly perturbed by interaction of one of the carbonyl groups with the MOF support. The spectra evidenced the formation of a weak hydrogen bonding interaction of the type mu(3)-OH center dot center dot center dot OCMo(CO)(5) involving the mu(3)-OH groups that are exclusively present in the tetrahedral cavities of the UiO-66 structure. The Mo(CO)(6) loaded MOFs are active and reusable pre-catalysts for cis-cyclooctene epoxidation, exhibiting excellent epoxide selectivity (up to quantitative epoxide yield within 1 h reaction) and tert-butyl hydroperoxide efficiency. Catalyst recycling and retention of structural integrity were demonstrated for UiO-66(Hf) loaded with 8.8 wt% Mo by the STI method. The UiO-66(Hf) host may be a better catalyst support than its Zr counterpart due its smaller crystallite size (similar to 100 nm) and higher defectivity. The substrate scope was broadened for Mo(8.8-STI)/Hf-MOF which promoted the epoxidation of biobased olefins (methyl oleate and DL-limonene) and oxidative dehydrogenation of cyclooctanol to cyclooctanone.
Mazo, M. AlejandraColomer, Maria T.Tamayo, AitanaRubio, Juan...
14页
查看更多>>摘要：Novel hierarchical micro-meso-macroporous fluorine-doped silicon oxycarbide derived materials have been obtained by HF etching of silicon oxycarbides pyrolyzed at different temperatures. The influence of etching time (1 or 24 h) and pyrolysis temperature (from 1100 to 1400 degrees C) on the selective removal of the silica nano-domains present in the silicon oxycarbide and the appearance of oxygen and fluorine functionalities have been determined and evaluated in terms of their electrochemical response. The insertion of fluorine in the silicon oxycarbide matrix (Si-O(F) bonds) and free carbon phase (C-F semi-ionic and C-F covalent bonds) was corroborated. The materials pyrolyzed at 1300-1400 degrees C and etched during 24 h show values of specific capacitance as high as 225-165 Fg(-1) (0.1-30 Ag-1) using a symmetrical configuration and H2SO4 1 M as electrolyte. These materials displayed energy density values of 28-19 Whkg(-1) (0.1-45 kWkg(-1)). The hierarchical microstructure in conjunction with the oxygen and fluorine functionalities are essential in order to explain their good electrochemical response. In particular, those materials present the highest amount of meso (3-10 nm) and larger meso-macropores and the highest content of fluorine in their composition. Then, fluorine-doped silicon oxycarbide derived materials can be potentially used as electrodes for supercapacitors in the field of energy storage applications.
查看更多>>摘要：Three zeolites ZSM-5, ZSM-35 and ZSM-22 are applied in n-butane cracking to reveal the influence of regional differences in Bronsted acid sites on reaction pathways. The Bronsted acid sites located in the channels of ZSM-5 exhibit a higher catalytic activity and yields to light olefins (especially the ethylene), which can be attributed to more relative contribution of bimolecular pathway. In comparison, more Bronsted acid sites are situated on the external surface or micropore mouths of ZSM-35 and ZSM-22, which are beneficial to propylene production. Note-worthily, almost no propane production on the two zeolites implies the predomination of monomolecular pathway. In situ FTIR technique further discloses that the difference in the reaction pathways is tailored by adsorption configurations of n-butane at two types of Bronsted acid sites. Under comparable conditions, the ZSM-5 performs a relatively good catalytic stability through bimolecular pathway. Furthermore, the correlation between deactivation rate and light olefins reveals that the enhancement of propylene selectivity accelerates the deactivation of ZSM-35 and ZSM-22. While, promotion on the ethylene selectivity is a significant inducement for the deactivation of ZSM-5.
查看更多>>摘要：Mechanochemical activation and steam-assisted interzeolite transformation offer a simple, fast and cost-efficient synthesis route to gmelinite (GME) zeolite. The use of faujasite (FAU) as the parent zeolite precursor facilitates the reaction and results in high yields of high-quality GME in less than 20 h under optimized conditions. The accessible porosity and amounts of stacking-faults were determined by N-2 physisorption and XRD analysis, respectively. The results show that the quality of the prepared materials easily competes with GME zeolites synthesized by conventional hydrothermal synthesis, which encourages further research in this area. By changing the reaction parameters, the approach may also be used for the production of several other types of zeolites, including MOR, MFI and ANA.
查看更多>>摘要：Inferior sintering-resistance of metal nanoparticles is an obstacle restricting the development of bifunctional catalysts in chemical industry. The construction of spatial architecture in zeolitic framework can enhance the stability of metal nanoparticles and prolong the service life of catalysts. A seed-directed solvent-free strategy was proposed here to prepare a metal-confined catalyst along the zeolitic framework to sterically encapsulate metal nanoparticles. The use of raw materials without extra solvents could improve synthetic efficiency of each kettle, reduce economic cost and decrease environmental pollution caused by organic solvents. The status of metal species was observed by aberration-corrected TEM images and XPS spectra, and the intracrystalline Pt species were speculated to isomorphically substitute the framework Al and P or occupy tens of micropore to form structural defect sites, leading to a decrease in the support acidity and a better balanced bifunctionality. While enhancing the metal stability, the maximum yield of isomer products was increased to 75% versus 63% for the conventional specimen synthesized by hydrothermal and post-impregnated method on n-dodecane hydro-isomerization. The results provide an efficient route to the synthesis of alternative bifunctional catalysts for n- alkanes hydroisomerization, and promote the high value-added conversion of downstream products in coal/ natural gas chemical industry.
NSTL
Elsevier