Ahmed R.AbdellahAbu-Bakr AAM.El-AdasyAhmed A.Atalla
9页
查看更多>>摘要：Nanoparticles,such as noble metal nanoparticles and covalent organic frameworks(COFs),advance heterogeneous catalysis.Three COFs were synthesized via the solvothermal method using tricarboxylic acids(tricarboxylic benzene(2,4,6-tri-p-carboxyphenyipyridine(H3L2),4,4',4"-tri carboxyl triphenylamine(H3LI),and trimesic acid(H3BTC))and l,3,5-triazine-2,4,6-triamine moieties.The synthesized COFs were potentially used as supports for the in-situ growth of palladium nanocrystals(Pd NCs),offering a particle size of 1-5 nm.X-ray diffraction(XRD),Fourier transforms infrared(FT-IR),transmission electron microscopy(TEM),high-resolution TEM(HR-TEM),nitrogen adsorption-desorption isotherms,thermogravimetric analysis(TGA),and X-ray photoelectron spectroscopy(XPS)characterized the materials.Using Heck cross-coupling reaction,Pd NCs@COFs were used as catalysts to synthesize different organic molecules via carbon-carbon(C-C)formation.They exhibit complete conversion(100%)for vinyl derivatives and aryl halides(Bromo-and Chloro-derivatives)with good stability.Pd NCs@COFs maintain high catalytic activity over four consecutive cycles.
查看更多>>摘要：Large amounts of radioiodine are released during spent nuclear fuel reprocessing and nuclear reactor accidents.Effective capture and long-term storage of volatile radioactive iodine from aqueous as well as in the vapor phase are imperative due to its inherent properties of a long half-life,environmental mobility and high toxicity.However,the development of a fast adsorption rate,high adsorption capacity and thermally stable radioiodine adsorption material remains a challenge.Herein,a novel core-shell Bi2S3 nanorods loaded ZIF-8 nanocrystals have been prepared via a facile,self-assembly procedure.The characteristics of as-synthesized Bi2S3@ZIF-8(BZ)nanocomposites were investigated by various techniques such as scanning electron microscopy-energy dispersive spectroscopy(SEM-EDS),powder X-ray diffraction(P-XRD)and Fourier transform infrared spectroscope(FT-IR)spectra,revealing ZIF-8 nanocrystals with an average size of 150 nm securely loaded on the surface of the Bi2S3 nanorods.Nitrogen sorption-desorption analysis showed that the as-synthesized BZ nanocomposites possess a high specific surface area(up to 1190.77 m~2 g~(-1)).The absorption experiments demonstrated that as-synthesized BZ nanocomposites exhibited excellent iodine adsorption capacities for vapor-phase iodine(2627.0 mg g~(-1)at 350 K and under ambient pressure within 6 h)and liquid-phase iodine(up to 786.4 mg g~(-1)within 14 h).The removal mechanism study revealed that the remarkable performance might be ascribed to the combined action of the large specific surface area of ZIF-8 crystals and the strong chemical interaction of Bi2S3 for I2 to form thermodynamically stable BiI3.Given these excellent iodine adsorption capacity,ease of preparation as well as good thermal stability,the BZ nanocomposites could be a promising candidate for radioactive iodine elimination.
查看更多>>摘要：CCVepoxide cycloaddition represents one of most attractive approaches for chemical fixation and utilization of CO2,but highly efficient and fully heterogeneous green catalysis is still challenging.Ionic metal-organic frameworks(IMOFs)are nice porous matrices heterogenizing the essential free nucleophilic anions and meanwhile providing Lewis acids,but the catalytic efficiency has been limited for low anion content and lack of auxiliary catalytic sites.In this work,we report stepwise optimization of IMOF catalysts by integrating multiple catalytic sites into MIL-101.Various monocationic IMOFs with quaternary ammonium and bromide anions were prepared by facile alkyne-azide click chemistry.Different numbers of hydroxyl groups were introduced in this ionization step to optimize the activity.To introduce more anions,dicationic IMOFs were created by a second ionization step,N-quaternization of triazolyl to triazolium.By the stepwise ionization and functionalization,we demonstrated the synergic catalytic effects among different sites,the impacts of hydroxyl/bromide content,and the size effect of the cationic group.The optimal IMOFs are superior to previous ionic heterogeneous catalysts in absence of cocatalysts.In particular,the dicationic catalyst can quantitatively convert epichlorohydrin to the carbonate within 1 h at 1 MPa CO2 and 80 ℃,the apparent turnover frequency being up to 478 h~(-1).The highly active and selective,fully heterogeneous and recyclable catalyst has the appeal for practical applications.
查看更多>>摘要：Two fluorine-containing conjugated microporous polymers(CMP-F)have been synthesized by Sonogashira coupling polymerization.The CMP-F powders show high yield,high porosity,high thermal stability,and high water contact angles up to 128°.Due to its high hydrophobicity,the CMP-F polymers are used as fillers for fabricating oil/water separation mixed-matrix membranes(MMMs).CMP-F/PI MMMs were prepared by the electrospinning method with polyimide as the matrix for the first time.The CMP-F/PI MMMs exhibited a high separation efficiency of at least 99.5% for all the tested oils,such as toluene,ethyl acetate,hexane,CCl4 and gasoline,against water.The maximum flux of hexane reached to 13500 L/(m~2·h),and the stability of the separation efficiency was maintained at approximately 99.5% for fifteen cycles.Surprisingly,the MMMs displayed highly-efficient diesel/water separation properties with separation efficiencies of up to 99.7%,although it is well known that it is difficult to efficiently separate diesel from water owing to its complex composition and high viscosity.In addition,a water-in-toluene emulsion could be separated by CMP-F/PI MMMs with a separation efficiency of up to 99.1%.CMP-F/PI MMMs have high potential for application in emulsion separation.
查看更多>>摘要：In the present work,mesoporous Al2O3-TiOx composites with different titania loadings(4,8 and 12 wt%)were synthesized to evaluate the effect of non-stoichiometric TiOx phases on the hydrodesulfurization(HDS)ability of the CoMo/Al2O3-TiOx catalysts.The activity of the catalysts was evaluated in the dibenzothiophene(DBT)HDS reaction carried out at 593 K,5.5 MPa in a batch reactor.Regardless of the TiOx content,all sulfided CoMo Al2O3-TiOx catalysts were more active than the C0M0/Al2O3 catalyst.For all catalysts,DBT HDS occurs mainly through the direct desulfurization(DDS)pathway(95-97% selectivity).The most active catalysts(CoMo-12 and CoMo-4)showed evidence of the presence of non-stoichiometric titanium oxides.The synthesized materials were characterized in depth to evaluate their crystallinity,textural and morphological properties,elemental composition and acidity.Their characterization showed that:(i),the Al2O3-TiOx interaction increased with decreasing TiOx content;(ii)the strong interaction between TiOx particles and alumina led to the formation of more defined TiOx structures;(iii),an increase in titania content led to the growth of TiOx crystals along the [101] direction(relative to the [001] direction),which in turn,led to the different TiOx morphologies: nanorods->> nanotubes-> U-shaped nanotubes.The TiCoMoS phase can be formed if the process is performed on Ti305 instead of TiO2.
查看更多>>摘要：Fly ash is a solid waste consisted of SiO2,Al2O3,CaO,Fe3O4 and trace amounts of heavy metal(Hg and Cd),therefore,their disposal could pose some threats to the environment.In this paper,the interzeolite transformation of NaA to ZSM-5 was explored as a low-cost and high value-added green process,where fly ash was resource utilized,and the conventionally high-cost silicalite-1 seeds and high-contamination organic amine were not required.Firstly,fly ash was activated with NaOH at high temperature,followed by the alkali-dissolving purification to remove the impurities.Then,purified fly ash was utilized to synthesize NaA at 110 ℃ for 12 h,and the transformations of NaA to ZSM-5 were conducted and the process parameters were optimized such as crystallization temperature,duration time,the content of additives such as ethanol or sodium chloride and the pretreatment of NaA,and so on.The results showed that the introduction of a trace amounts of NaCl or EtOH could greatly facilitate the growth of ZSM-5,and the high crystalline ZSM-5 molecular sieves were successfully obtained at 160 ℃ for 36 h with the comparable textual properties to the commercial ZSM-5.Finally,an assembly mechanism of MFI framework in the interzeolite transformation of NaA to ZSM-5 was proposed.
查看更多>>摘要：Porphyrin with atomic-level thickness and uniform pore size hasn't yet been studied for the separation of gas molecules,especially for proton isotopes.Herein,we Computationally designed O,S,and Se doped hetero-porphyrin to evaluate its kinetic energy barrier and molecular level insight of the permeation pathway for protium ion and relevant isotopes.Zero-point energy(ZPE)for protium ion isotopes was observed at the transition state while Arrhenius equation has been used to calculate the tunneling ratio of H~+/D~+ and H~+/T~+.Among all investigated hetero-porphyrins,0-0 doped derivative provided the most valuable results with tunneling ratio of 23 and 30 respectively with no energy barrier.
查看更多>>摘要：In aramid nanofibers(ANFs)aerogels,poly(vinyl alcohol)(PVA)was used as an aid molding agent.This study demonstrated that implementing PVA could result in a tunable pore structure of ANFs aerogels and the uniform pore was designed for thermal insulation and adsorption composites.Here,the electron microscope revealed well-preserved pores in the PVA/ANF composites aerogel which achieved extremely low thermal conductivity and excellent rebound resilience of composite aerogel.The PVA1/ANF composite aerogel had ultralow density(9.98 kg/m~3),low thermal conductivity(25.78 mW/m-K)and excellent mechanical properties.In addition,the elastic PVA/ANF composite aerogels are excellent adsorbers for organic pollutants and have high reusability.The hardness with softness combination results presented in this work can be used to further improve the performance of ANF aerogel and have reference significance for the design of other composite materials.
查看更多>>摘要：ZnMn2O4@Mo6S_(9.5)hierarchical mesoporous microflowers have been constructed for anode applications in Li-ion batteries(LIBs).Ultrathin Mo6S_(9.5)nanosheets have grown on ZnMn2O4 microspheres by hydrothermal method and calcination process to synthesis ZnMn2O4@Mo6S_(9.5)hierarchical mesoporous microflowers(HMMs).The initial discharge/charge capacities of ZnMn2O4@Mo6S_(9.5)HMMs were 1203/846 mA h g~(-1).After high-current cycles,reversible capacity was 731 mA h g~(-1)at 100 mA g~(-1),which was close to that of the first 10 turns.The excellent performance could be ascribed to the synergistic effect among ZnMn2O45 Mo6S_(9.5)and the 3D hierarchical architecture.The results demonstrate that ZnMn2O4@Mo6S_(9.5)HMMs have broad application prospect as electrochemical energy storage device.
查看更多>>摘要：The cycloaddition of CO2 to epoxides is now becoming one of the most important CCVfixation reactions due to the 100% atom efficiency together with the wide application of cyclic carbonates.However,such a cycloaddition reaction often requires efficient catalysts owing to the intrinsically inert nature of CO2.Herein,we report the synthesis of triphenylimidazolium-incorporated,benzbisimidazole-linked porous organic polymer(namely PBPI-IL)by polycondensation of 1,2,4,5-benzenetetramine with triphenylimidazole-containing tetraaldehyde followed by post-treatment with iodomethane.The as-synthesized PBPI-IL2 network with intact benzbisimidazole ring possesses an ionization degree of 31.94 mol% and a specific surface area of 350 m~2 g~(-1),which is capable of efficiently catalyzing the cycloaddition of CO2 to epoxides,i.e.,99% conversion and 99% selectivity in the transformation of epichlorohydrin at 60 ℃ under atmospheric CO2 pressure.Moreover,the PBPI-IL2 network can be readily recycled and reused for at least 6 times.The highly catalytic activity of PBPI-IL2 network can be ascribed to the H-bonding interaction between benzbisimidazole ring and epoxides,the Lewis base-Lewis acid and ju-ju bonding interactions between benzbisimidazole ring and CO2 molecule,as well as the high nucleophi-licity of I~ anion.
NSTL