查看更多>>摘要：Facile preparation of N-doped hierarchically porous carbons(NHPCs)is an important research direction in high-performance supercapacitors(SCs).In this paper,we report a high internal phase emulsion(HIPE)template method to prepare NHPCs from melamine resins with the aid of sucrose or glucose,referred as S-NHPCs or G-NHPCs,respectively.Sucrose or glucose,formaldehyde,and melamine are dissolved in water as the continuous phase of the HIPE.Under acid catalysis,the continuous phase is cross-linked through aldimine condensation to produce porous melamine resins.Meanwhile,carbohydrate is incorporated via the interaction between the rich oxygen-containing functional groups(-OH,-C=OH)of carbohydrate and the-NH2 groups of melamine through hydrogen bonding and acetal reaction.After carbonization and activation,S-NHPCs or G-NHPCs with high specific surface areas(SSA)are obtained respectively.Besides regulating the porous morphology,biomass carbohydrate can enhance the electrochemical properties of NHPCs via increasing the SSA and hydrophilicity of NHPCs.The SSA of S-NHPC and G-NHPC increased notably from 823 to 1682 m~2 g"1 and 1913 m~2 g"1,respectively.Meanwhile,owing to the comprehensive N-doping and the developed porous structure,the prepared NHPC based electrodes exhibit excellent specific capacitances(up to 305 F g~(-1)at 1 A g~(-1)),satisfactory cycling stability,and remarkable rate performance in a three-electrode system.
查看更多>>摘要：Although zeolites are well-accepted as environmentally friendly catalysts for the isobutane alkylation,the structure-performance relationship between C4 reactants(isobutane and butene)and zeolites is less reported.Herein,the adsorption and diffusion behaviors of C4 reactants on zeolites with different topologies were investigated using configuration bias Monte Carlo(CBMC)and molecular dynamics(MD)simulations under experimental conditions in 348 K and 2.5 MPa.It is revealed that surface area,largest cavity diameter,and pore limiting diameter are the most relevant structural parameters for zeolites to determine the adsorption and diffusion of C4 reactants.In addition,the dimensions of the zeolitic channels can also affect the selectivity of isobutane to butene and the diffusion of C4 reactants,thereby affecting the process of isobutane alkylation reaction.This work can provide a good reference for the design of novel zeolites for isobutane alkylation.
Lowell Toku Kokuloku JrElvis Djam MiensahAotian Gu
12页
查看更多>>摘要：In the application of nuclear technology,radioiodine,a key radionuclide is released into the environment.Its danger to environmental and human health,such as hyperthyroidism,high environmental mobility,and human metabolic damage,makes its capture and safe storage very important.Herein,we make a broad critical review of the strategies adopted to enhance the functionality and performance of MOFs and their derived materials for radioiodine capture.The review also revealed the need to fabricate these materials into more robust modes and optimize their synthesis to improve radiation stability; in order to significantly overcome the challenge of their deployment in practical applications.Moreover key contributions to the research upon which most developmental research is based are highlighted to reveal gaps and focus future research.
查看更多>>摘要：Metal-modified zeolites and function-matched metal organic frameworks(MOFs)have been adapted to different scenarios of sulfides capture in order to meet increasingly stringent quality requirements and environmental regulations.However,achieving enhanced performances of both adsorption capacity and moisture resistance is still challenging.In this study,we provided an approach to the synthesis of AgY@Cu-BTC hybrid composite for enhanced sulfides capture and moisture resistance.Multiple characterizations confirmed the hybrid structure of AgY@Cu-BTC.Additionally,computational simulation and dynamic adsorption measurement were combined to evaluate the adsorption of several typical sulfides on synthesized adsorbents,and reveal the competitive adsorption mechanism.Both Ag species and ethanol solvent lead to the partial reduction of Cu(II)to Cu(I)within the AgY@Cu-BTC framework.The dynamic adsorption capacity of the AgY@Cu-BTC is 1.54 times and 1.38 times higher than those of the parent AgY and Cu-BTC,respectively.Moreover,the AgY@Cu-BTC retains much more adsorption capability for sulfides than the AgY sample with the same water content.Present study highlights the competitive adsorption of various sulfides on the hybrid structures as well as the influences of pre-adsorbed water on sulfide adsorption,and provides insights into the function-oriented development of adsorption materials.
查看更多>>摘要：Purposive regulation of the spatial location and distribution of acid sites in a zeolite catalyst,though still rather challenging,has proved to be an effective measure to enhance its performance in the conversion of methanol to olefins(MTO).Herein,a series of ZSM-11 zeolites were synthesized using different sodium halides(with tetra-butylammonium hydroxide(TBAOH)as the structure-directing agent); the effect of halogen anions(CI~-,Br~-and I~-)in the synthesis gel on the Al siting and thereon the spatial location and distribution of acid sites in the ZSM-11 zeolites as well as their relation to the catalytic performance in MTO was elaborately investigated.The results indicate that for the synthesis of high Si/Al ratio ZSM-11 zeolites(Si/Al>60),the CI~-anions present in the synthesis gel can induce more Al atoms siting on the external surface of ZSM-11 crystals,thereby leading to a short catalytic lifetime in MTO due to the rapid coke deposition.In contrast,larger Br~-or I~-anions in the synthesis gel,owing to their stronger covalent interaction with the TBA~+ cations,may moderate the formation of crystal silicate nuclei and lead to a uniform distribution of Al species in the inner straight channels,which can effectively suppress the surface coke deposition and inhibit the aromatic-based cycle for MTO.As a result,the high Si/Al ratio ZSM-11 zeolites obtained with Br~-or I~-in the synthesis gel exhibit much better catalytic stability in MTO and higher selectivity to propene and butene,in comparison with the ZSM-11 counterpart synthesized using Cl".These results help to clarify the relation between the catalytic performance of ZSM-11 in MTO and the location of acid sites and thus bring forward a facile strategy to enhance the catalytic performance of zeolites through purposively regulating the spatial distribution of acid sites.
查看更多>>摘要：The zeolite frameworks(FER,TON,CHA,and IFR)with a large diversity of the IR band shapes in the OH stretching region were investigated by combined use of FT-IR spectroscopy and DFT calculations.The analysis of various isolated Br0nsted acid sites was performed with a model based on Boltzmann weighted relative energies and OH frequencies obtained by the ω/r correlation method.This approach has recently been used to reveal the non-statistical incorporation of aluminum into the H-MOR framework.The model correctly predicts the band shapes of H-FER and H-TON zeolites in the free OH region of the FT-IR spectra.For H-CHA and H-IFR,however,the mutual BAS interactions cannot be ignored even for high Si/Al ratios,which renders the concept of isolated BAS inadequate.Thus,the periodic calculations of adsorption and catalytic properties of zeotype frameworks should always be carried out with extended models mimicking real heteroatom distribution in these materials.
查看更多>>摘要：We present detailed ONIOM(ωB97X-D:PM6)calculations for the formation mechanism of novel composites combining protonic mordenites(H-MOR)with various ionic liquids:1,3-dimethyl-imidazolium chloride[MMIm] CI,1-ethyl-3-methyl-imidazolium chloride[EMIm] CI; l-methyl-3-propyl-imidazolium chloride[PMIm]Cl; 1-butyl-3-methyl-imidazolium chloride[BMImJCl,1-(2-hydroxyethyl)-3-methyl-imidazolium chloride[HEMIm] CI,1,3-dimethyl-1,3,2-diazasilolium chloride[MMSiN]Cl,and l,3-dimethyl-1,3-diphospholium chloride[MMPP] Cl.The most feasible[MJ-MOR formation mechanism([M]~+ =[MMIm]~+,[EMIm]~+,[PMIm]~+,[BMIm]~+,[HEMIm][MMSiN]~+[MMPP]~+)involves an ion exchange at the T4010 position favoring the isolation of a minimal number of[M]~+ isomers(i.e.,conformational traps).The interaction of these[M]-MOR composites with pollutant gases has afterward been evaluated.Among the studied sytems,[EMIm]-MOR and[HEMIm]-MOR present electronic and steric conditions for potential applications in gas separation,capture,and storage(H2 and H2S).The H-MOR framework exhibits two structural conformers with the[HEMIm]~+ cation in the confined space.Both,the MOR-T4O10-[HEMIm] and MOR-T4O10-[HEMIm]~(HB)conformers,interconvert by a dynamic equilibrium with a transition state MOR-T4010-TS1 acting as a conformational switch(ON~OFF)that selectively recognizes and captures H2S through a plier-like conformation.
查看更多>>摘要：Although vanadium redox flow batteries hold great promise for energy storage systems,Nafion(being a conventional membrane material)requires improvement in terms of the crossover phenomenon.Herein,a nano-porous metal-organic framework(MOF)is applied as a membrane for vanadium redox flow batteries via addition of the MOF to a Nafion solution to prepare Nafion/MOF composite membranes via casting.Composite membranes are fabricated into a Nafion matrix by introducing small amounts of CAU-10-X(X =-OH,-CH3,-OS1,-OS2),an Al-based MOF synthesized with ligands having hydroxyl,methyl,and a combination of hydroxyl and sulfonic acid functional groups.The membrane physicochemical properties(such as water uptake,swelling ratio,ion exchange capacity,proton conductivity,and electrochemical properties from charge-discharge experiments on a single cell)are compared and evaluated.In 100 charge-discharge cycles of the single cell at a current density of 160 mA cm~(-2),the composite membrane N/CAU-10-OSl with 0.6 wt% dispersed MOF and a combination of hydroxyl and sulfonic acid functional groups exhibits capacity retention of 80.34% and energy efficiency of 77.56% at approximately 50 μm thickness.These values are better those achieved by commercial separation membrane Nafion 115 with 127 μm thickness tested under identical conditions and the proposed membrane is thus expected to be economically advantageous.
查看更多>>摘要：Polysaccharide nanorods(chitin,cellulose)can be used as colloidal templates to form silica-based mesoporous materials by combining self-assembly and sol-gel chemistry.Chitin nanorods are chosen here for their self-assembly properties,facile preparation from natural resources,and because of the complexing properties of the free amino groups at their surface in view of further functionalization.Electrospinning of ethanolic co-suspensions,containing the chitin nanorods as pore templates,siloxane oligomers as silica precursors and polyvinylpyrrolidone(PVP)as spinning polymer,allows for forming mats of hybrid organic-inorganic fibers with diameters in the 200-300 nm range.The relative proportions of each component can be adjusted to meet specific characteristics(e.g.micro-/mesoporosity ratio).After calcination,the fibers present an open porosity studied by TEM and N2 volumetry.Elongated mesopores(100-200 nm long,2-4 nm wide)are created by individual chitin monocrystals forming the nanorods.They are highly oriented along the fibers'axes with orientational order parameters P2>0.95 for volume chitin contents(pchitin>0.2.Additional microporosity is provided by the removal of the spinning polymer,PVP.Complementary viscosity measurements on the initial co-suspensions allow discussing the interactions between colloids and their possible impact on the materials'textures observed.The introduction of a monomeric Ti~(4+)precursor in the co-suspensions leads to isolated and tetrahedral Ti units,distributed in the calcined porous silica fibers and possibly close to the pores surface.In addition,preliminary investigations on processing the fibers with a Zn xanthate as ZnS precursor leads to carbonized fibers with nanoparticles and a Zn/S molar ratio close to 1.
查看更多>>摘要：Knitting method has been widely used in the synthesis of microporous organic polymers(MOPs)because of its simple process and wide adaptability.In our study,microporous organic biphenyl(MOBP)and F-containing microporous organic fluorobiphenyl(MOFBP)were prepared in this way.The two polymers show large BET surface area(917 m~2 g~(-1)),pore volume(0.77 cm~3 g~(-1))and favorable phase change materials(PCMs)capacities.Shape stable phase change composites were obtained using self-adsorption method.From differential scanning calorimetry(DSC),thermal gravimetric analysis(TGA)and X-ray diffraction(XRD)results,the PCM composites have favorable encapsulation ratios,thermal stabilities and latent heats.For stearyl alcohol@ MOFBP(SA@MOFBP),the encapsulation ratio is 78.9 wt% and the latent heat reaches 194.3 kJ g~(-1).Moreover,all composites remained their thermal energy storage properties after 100 thermal cycles.These PCM composites have potential applications in the field of thermal energy storage.
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