Bimetallic nanoparticles exhibit a synergistic effect that critically depends on their surface composition,but such promotion mechanisms become vague with varying surface compositions.Here,alumina supported Ag@Pd core...Bimetallic nanoparticles exhibit a synergistic effect that critically depends on their surface composition,but such promotion mechanisms become vague with varying surface compositions.Here,alumina supported Ag@Pd core–shell and PdAg alloy structure with controlled size and surface compositions were prepared to demonstrate synergetic mechanisms,particularly,ligand and strain effects on activity and ethylene selectivity for acetylene hydrogenation.The performance evaluation indicates that Ag@Pd catalysts with well-controlled Pd-shell thickness can effectively lower apparent activation energy and improve ethylene selectivity.Hydrogenation activity increases from 0.019 to 0.062 s^(-1) with decreasing Pd-shell thickness under mild conditions,which is 3–6 times higher than their alloyed and monometallic counterparts.Combined characterizations and density functional theory are conducted to reveal such shell-thickness-dependent performance.The ligand effect arising from Ag alloying in the interface of Ag@Pd2ML observes the strongest binding of acetylene,but it diminished sharply and the strain effect gets more prevailing with increasing shell thickness.The competition of ethylene desorption and deephydrogenation were also investigated to understand the selectivity governing factors,and the selectivity descriptor(0.5BE(C_(2)H_(4))–BE(H))was built to match the contribution of ligand and strain effect on the different surfaces of Pd-Ag bimetallic NPs.The exploration of synergetic mechanisms among bimetallic NPs with varied structure and surface compositions in this work can help us to deepen the understanding catalyst structure–activity relationship and provide a feasible way to optimize the overall catalytic performance.展开更多
Amorphous carbons are promising anodes for high-rate potassium-ion batteries.Most low-temperature annealed amorphous carbons display unsatisfactory capacities.Heteroatom-induced defect engineering of amorphous carbons...Amorphous carbons are promising anodes for high-rate potassium-ion batteries.Most low-temperature annealed amorphous carbons display unsatisfactory capacities.Heteroatom-induced defect engineering of amorphous carbons could enhance their reversible capacities.Nevertheless,most lignocellulose biomasses lack heteroatoms,making it a challenge to design highly heteroatom-doped carbons(>10 at%).Herein,we report a new preparation strategy for amorphous carbon anodes.Nitrogen/sulfur co-doped lignin-derived porous carbons(NSLPC)with ultra-high nitrogen doping levels(21.6 at%of N and 0.8 at%of S)from renewable lignin biomacromolecule precursors were prepared through a supramolecule-mediated pyrolysis strategy.This supermolecule/lignin composite decomposes forming a covalently bonded graphitic carbon/amorphous carbon intermediate product,which induces the formation of high heteroatom doping in the obtained NSLPC.This unique pyrolysis chemistry and high heteroatom doping of NSLPC enable abundant defective active sites for the adsorption of K+and improved kinetics.The NSLPC anode delivered a high reversible capacity of 419 mAh g^(-1)and superior cycling stability(capacity retention of 96.6%at 1 A g^(-1)for 1000 cycles).Potassiumion hybrid capacitors assembled by NSLPC anode exhibited excellent cycling stability(91%capacity retention for 2000 cycles)and a high energy density of 71 Wh kg^(-1)at a power density of 92 W kg^(-1).展开更多
Ce-encapsulated Beta zeolite was synthesized by a one-pot hydrothermal method with citric acid complexing Ce in the absence of Na species.Additional citric acid can effectively prevent the deposition of Ce species dur...Ce-encapsulated Beta zeolite was synthesized by a one-pot hydrothermal method with citric acid complexing Ce in the absence of Na species.Additional citric acid can effectively prevent the deposition of Ce species during the hydrothermal synthesis of zeolites,leading to uniform distribution of Ce cluster in the framework of Beta zeolites.Moreover,the sodium-free synthesis system resulted that the Brønsted acid sites were mainly located on the straight channels and external surface of Beta zeolites,improving the utilization of Brønsted acid sites.In addition,Ce encapsulated Beta zeolites showed enhanced activity and robust stability in the alkylation of benzene with 1-dodecene based on the synergistic effect between Ce species and Brønsted acid sites,which pave the way for its practical application in the production of alkylbenzene.展开更多
There have been reports about Fe ions boosting oxygen evolution reaction(OER)activity of Ni-based catalysts in alkaline conditions,while the origin and reason for the enhancement remains elusive.Herein,we attempt to i...There have been reports about Fe ions boosting oxygen evolution reaction(OER)activity of Ni-based catalysts in alkaline conditions,while the origin and reason for the enhancement remains elusive.Herein,we attempt to identify the activity improvement and discover that Ni sites act as a host to attract Fe(Ⅲ)to form Fe(Ni)(Ⅲ)binary centres,which serve as the dynamic sites to promote OER activity and stability by cyclical formation of intermediates(Fe(Ⅲ)→Fe(Ni)(Ⅲ)→Fe(Ni)-OH→Fe(Ni)-O→Fe(Ni)OOH→Fe(Ⅲ))at the electrode/electrolyte interface to emit O_(2).Additionally,some ions(Co(Ⅱ),Ni(Ⅱ),and Cr(Ⅲ))can also be the active sites to catalyze the OER process on a variety of electrodes.The Fe(Ⅲ)-catalyzed overall water-splitting electrolyzer comprising bare Ni foam as the anode and Pt/Ni-Mo as the cathode demonstrates robust stability for 1600 h at 1000 mA cm^(-2)@~1.75 V.The results provide insights into the ioncatalyzed effects boosting OER performance.展开更多
The lithiated covalent organic framework(named TpPa-SO_(3) Li),which was prepared by a mild chemical lithiation strategy,was introduced in poly(ethylene oxide)(PEO)to produce the composite polymer electrolytes(CPEs).L...The lithiated covalent organic framework(named TpPa-SO_(3) Li),which was prepared by a mild chemical lithiation strategy,was introduced in poly(ethylene oxide)(PEO)to produce the composite polymer electrolytes(CPEs).Li-ion can transfer along the PEO chain or across the layer of TpPa-SO_(3) Li within the nanochannels,resulting in a high Li-ion conductivity of3.01×10^(-4)S/cm at 60℃.When the CPE with 0.75 wt.%TpPa-SO_(3) Li was used in the LiFePO_(4)‖Li solid-state battery,the cell delivered a stable capacity of 125 mA·h/g after 250 cycles at 0.5 C,60℃.In comparison,the cell using the CPE without TpPa-SO_(3) Li exhibited a capacity of only 118 mA·h/g.展开更多
As one of the most common cathode materials for aqueous zinc-ion batteries(AZIBs),manganese oxides have the advantages of abundant reserves,low cost,and low toxicity.However,the electrochemical mechanism at the cathod...As one of the most common cathode materials for aqueous zinc-ion batteries(AZIBs),manganese oxides have the advantages of abundant reserves,low cost,and low toxicity.However,the electrochemical mechanism at the cathode of aqueous zinc-manganese batteries(AZMBs) is complicated due to different electrode materials,electrolytes and working conditions.These complicated mechanisms severely limit the research progress of AZMBs system and the design of cells with better performance.Hence,the mechanism of AZMBs currently recognized by most researchers according to the classification of the main ions involved in the faradaic reaction is introduced in the review.Then a series of reasons that affect the electrochemical behavior of the battery are summarized.Finally,the failure mechanisms of AZMBs over prolonged cycling are discussed,and the current insufficient research areas of the system are explained,along with the direction of further research being prospected.展开更多
BiVO_(4)is one of the most promising photoanode materials for photoelectrochemical(PEC)solar energy conversion,but it still suffers from poor photocurrent density due to insufficient light‐harvesting efficiency(LHE),...BiVO_(4)is one of the most promising photoanode materials for photoelectrochemical(PEC)solar energy conversion,but it still suffers from poor photocurrent density due to insufficient light‐harvesting efficiency(LHE),weak photogenerated charge separation efficiency(Φ_(Sep)),and low water oxidation efficiency(Φ_(OX)).Herein,we tackle these challenges of the BiVO_(4)photoanodes using systematic engineering,including catalysis engineering,bandgap engineering,and morphology engineering.In particular,we deposit a NiCoO_(x)layer onto the BiVO_(4)photoanode as the oxygen evolution catalyst to enhance theΦ_(OX)of Fe‐g‐C_(3)N_(4)/BiVO_(4)for PEC water oxidation,and incorporate Fe‐doped graphite‐phase C_(3)N_(4)(Fe‐g‐C_(3)N_(4))into the BiVO_(4)photoanode to optimize the bandgap and surface areas to subsequently expand the light absorption range of the photoanode from 530 to 690 nm,increase the LHE andΦ_(Sep),and further improve the oxygen evolution reaction activity of the NiCoO_(x)catalytic layer.Consequently,the maximum photocurrent density of the as‐prepared NiCoO_(x)/Fe‐g‐C_(3)N_(4)/BiVO_(4)is remarkably boosted from 4.6 to 7.4 mA cm^(−2).This work suggests that the proposed systematic engineering strategy is exceptionally promising for improving LHE,Φ_(Sep),andΦ_(OX)of BiVO_(4)‐based photoanodes,which will substantially benefit the design,preparation,and large‐scale application of next‐generation high‐performance photoanodes.展开更多
Up to now,three kinds of ion-storage mechanisms are summarized towards anode materials in lithium/sodium-ion batteries,but they have low capacity and poor cyclic performance.Therefore,it is necessary to develop a new ...Up to now,three kinds of ion-storage mechanisms are summarized towards anode materials in lithium/sodium-ion batteries,but they have low capacity and poor cyclic performance.Therefore,it is necessary to develop a new approach to optimize ion storage.Herein,we report an adsorption/desorption storage route through engineering electronic structure of cation-deficient Ti_(1-x)O_(2)nanosheets.Ti_(1-x)O_(2)nanosheets indeed exhibit higher capacity(332.1 mA h g^(-1)vs.137.7 mA h g^(-1)for LIBs,195.7 mA h g^(-1)vs.111 mA h g^(-1)for SIBs),and more stable cyclic performance(296 mA h g^(-1)vs.99 mA h g^(-1)for LIBs,178.1 mA h g^(-1)vs.80.2 mA h g^(-1)for SIBs after 100 cycles)at 0.1 A g^(-1)than TiO_(2)nanosheets.Kinetics analysis and density functional theory(DFT)calculations reveal that electronic structures of vacancy within Ti_(1-x)O_(2) nanosheets encourage a novel adsorption-desorption storage route.These results highlight the benefits of the engineered electronic structures within electrode material and implement novel ion-storage mechanism towards broad energy storage applications.展开更多
Zinc ion hybrid capacitors(ZIHCs), which integrate the features of the high power of supercapacitors and the high energy of zinc ion batteries, are promising competitors in future electrochemical energy storage applic...Zinc ion hybrid capacitors(ZIHCs), which integrate the features of the high power of supercapacitors and the high energy of zinc ion batteries, are promising competitors in future electrochemical energy storage applications. Carbon-based materials are deemed the competitive candidates for cathodes of ZIHC due to their cost-effectiveness, high electronic conductivity, chemical inertness, controllable surface states, and tunable pore architectures. In recent years, great research efforts have been devoted to further improving the energy density and cycling stability of ZIHCs. Reasonable modification and optimization of carbon-based materials offer a remedy for these challenges. In this review, the structural design, and electrochemical properties of carbon-based cathode materials with different dimensions, as well as the selection of compatible, robust current collectors and separators for ZIHCs are discussed. The challenges and prospects of ZIHCs are showcased to guide the innovative development of carbon-based cathode materials and the development of novel ZIHCs.展开更多
Cobalt-rich perovskite oxides play a paramount role in catalyzing oxygen evolution reaction(OER)on account of their acceptable intrinsic activity but are still challenging due to the high costs and undesired stability...Cobalt-rich perovskite oxides play a paramount role in catalyzing oxygen evolution reaction(OER)on account of their acceptable intrinsic activity but are still challenging due to the high costs and undesired stability.In response to the defects,herein,the Mg-incorporated perovskite cobaltite SrCo_(0.6)Fe_(0.3M)g_(0.1)O_(3-δ)(SCFM-0.1)is proposed as a novel earth-abundant and durable OER electrocatalyst.A well-consolidated cubic-symmetry structure and more active oxygen intermediates are enabled upon Mg substitution.Hence,the optimized SCFM-0.1 perovskite oxide achieves prominent OER electrocatalytic performance,that is,a low overpotential of only 320 mV at 10 mA cm^(-2),a small Tafel slope of 65 mV dec^(-1),as well as an outstanding durability within 20 h,substantially outperforming that of the pristine SrCo_(0.7)Fe_(0.3)O_(3-δ)and benchmark Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3-δ)and IrO_(2) catalysts.The strong pHdependent behavior associated with lattice oxygen activation mechanism for SCFM-0.1 catalyst is also confirmed.This work paves a unique avenue to develop cost-effective and robust perovskite cobaltites for efficient OER electrocatalysis.展开更多
The development of polyoxometalates for olefin oxidation is critical to achieving the green chemical process of the C5 fraction further processing.Di-lacunary silicotungstic anions were easily obtained by continuously...The development of polyoxometalates for olefin oxidation is critical to achieving the green chemical process of the C5 fraction further processing.Di-lacunary silicotungstic anions were easily obtained by continuously adjusting the p H instead of the traditional step-by-step method,which exhibited excellent performance in the catalytic oxidation of cyclopentene(CPE)to aldehydes or alcohols.The 93.69%CPE conversion and 97.15%total product selectivity(41.38%for glutaraldehyde(GA)and 55.77%for 1,2-cyclopentanediol(1,2-diol)were achieved by using H_(2)O_(2)as the oxidant and acetonitrile as the solvent.Through complementary characterization,it was found that the optimized di-lacunary silicotungstic polyoxometalate retained a complete Keggin structure,and exhibited better catalytic activity and stability than the mono-lacunary or saturated silicodecatungstate because it exposed more catalytic active centers.Furthermore,in situ FT-IR spectra was utilized to monitor the reaction process,revealing the formation of the active species W(O_(2))on the di-lacunary silicotungstic polyoxometalate and the intermediate epoxycyclopentane during the catalytic oxidation of cyclopentene.展开更多
Novel organo-inorganic hybrid materials(MTW-x-SO_(3)H) have been fabricated by immobilizing 3-mercap topropyltriethoxysilane onto mesopore MTW zeolites, which is treated via a simple oxidation process with hydrogen pe...Novel organo-inorganic hybrid materials(MTW-x-SO_(3)H) have been fabricated by immobilizing 3-mercap topropyltriethoxysilane onto mesopore MTW zeolites, which is treated via a simple oxidation process with hydrogen peroxide as the oxidant to transform sulfhydryl group into sulfonic acid group. The organic sulfhydryl groups are covalently bonded to the external surface of MTW zeolites through the condensation between siloxane arising from organic fragments with silanol groups on the surface of MTW zeolites, the hybrids contain sulfonic acid group within the external surface of MTW zeolites and an opened mesoporous system in the matrix of MTW zeolites, which provide enough accessible Brùnsted acid sites for the alkylation between phenol with tert-butyl alcohol. Through this methodology it's possible to prepare multifunctional materials where the plenty of mesopores are benefit for the introduction of larger numbers of sulfonic acid groups that contributes to activity during reactions, resulting in high activity(>55%) of MTW-4-SO_(3)H and desired selectivity(>56%) of 2-TBP(2-tert-butyl phenol) in the alkylation between phenol with tert-butyl alcohol.展开更多
Adsorption and separation of C_(4) hydrocarbons are crucial steps in petrochemical processes.Employment of porous materials for enhancing the separation efficiency have paid much attention.Covalent-organic frameworks ...Adsorption and separation of C_(4) hydrocarbons are crucial steps in petrochemical processes.Employment of porous materials for enhancing the separation efficiency have paid much attention.Covalent-organic frameworks of diamond-topology,dia-COFs,often exhibit unique structural properties such as interpenetration isomerism and pedal motion.Herein,in order to get a deep insight into the structure-performance correlation of such dia-COFs,a series of dia-COF materials have been proposed and theoretically investigated on the C_(4) separation.It is found that these dia-COFs display an excellent adsorption and separation property towards isobutene with respect to other C_(4) hydrocarbons(i.e.,1,3-butadiene,1-butene,2-cis-butene,2-trans-butene,isobutane and n-butane).What’s more,the correlation between the topology parameters and experimental synthesis feasibility has been established for COF-300(dia-cN),and the unreported COF-300(dia-c3) is predicted to be experimentally feasible synthesized.Our findings not only provide a deep insight into the mechanism of topology characteristics of dia-COFs on C_(4) adsorption and separation properties but also guide the design and synthesis of novel highly-effective porous materials.展开更多
With advantages of low costs and high energy density,Li–S batteries are considered as one of the most promising energy storage devices.However,Li_(2)S_(2) with a high dissociation energy and insulative properties is ...With advantages of low costs and high energy density,Li–S batteries are considered as one of the most promising energy storage devices.However,Li_(2)S_(2) with a high dissociation energy and insulative properties is hard to convert into Li_(2)S,resulting in underutilization of sulfur capacity.Herein,Co-Mo_(2)C@C yolk–shell spheres as nanoreactors were designed to confront this challenge rationally.The Co-Mo_(2)C@C-induced Li_(2)S_(1/2) nucleation and growth in the three-dimensional process and the cathode produced more Li_(2)S after full discharge.Experimental studies and theoretical calculations reveal that the conversion barrier from Li_(2)S_(2) into Li_(2)S was lowered while the diffusion of lithium ions and electron transfer accelerated when using the Co-Mo_(2)C@C catalyst.Based on the above advantages,the Co-Mo_(2)C@C/S cathode exhibits a high reversible capacity and excellent cyclic stability,such as an initial specific capacity of 1200 mAh g^(−1) at 0.1 C with 709 mAh g^(−1) at 1.0 C after 1000 cycles with a low capacity fading rate of 0.04%per cycle.Even at high densities of 3.0 C and 5.0 C,the specific capacities are 647.6 and 557.7 mAh g^(−1) after 400 cycles,respectively.Impressively,it also shows ca.770 and 900 mAh g^(−1) at 0.2 C after 50 cycles with high sulfur loadings of 4.2 and 5.1 mg cm−2,respectively.The present work may provide new insights into the design of nanoreactors to promote Li_(2)S_(1/2) growth in a three-dimensional process and accelerate conversion from solid Li_(2)S_(2) to solid Li_(2)S in high performance Li–S batteries.展开更多
非化学计量微米氧化硅(SiO_(x))由于其高理论容量和低成本,有望成为锂离子电池石墨负极材料的替代品.然而,SiO_(x)的实际应用仍然受到其较差的固有导电性和循环过程中明显的体积变化的阻碍.在本工作中,为了同时解决这些问题,我们使用可...非化学计量微米氧化硅(SiO_(x))由于其高理论容量和低成本,有望成为锂离子电池石墨负极材料的替代品.然而,SiO_(x)的实际应用仍然受到其较差的固有导电性和循环过程中明显的体积变化的阻碍.在本工作中,为了同时解决这些问题,我们使用可规模化的溶剂热和热还原方法制备了具有TiO_(1-y)Ny-C涂层的SiO_(x)基负极材料(SiO_(x)@TiON-C).我们通过系统性研究发现,TiO_(1-y)Ny-C涂层可以适应SiO_(x)循环过程中大的体积变化且有效提高其导电性.因此,SiO_(x)@TiON-C负极具有突出的储锂性能.具体而言,SiO_(x)@TiON-C负极可以在500 mA g^(-1)的电流密度下循环500圈后仍保持750.2 mA h g^(-1)的优异可逆容量,75.1%的初始库仑效率和优异的倍率性能.这项工作为促进下一代锂离子电池微米SiO_(x)基负极材料的实际商业化提供了一种很有前途的方法.展开更多
Bismuth(Bi),as an alloy-based anode material,has attracted much atte ntion in the developme nt of sodiumion hybrid capacitors(SIHCs)due to its high theoretical capacity.However,the volume expansion of the Bi-based ano...Bismuth(Bi),as an alloy-based anode material,has attracted much atte ntion in the developme nt of sodiumion hybrid capacitors(SIHCs)due to its high theoretical capacity.However,the volume expansion of the Bi-based anode during the sodiation/desodiation process results in limited rate capability.In the present work,a porous Bi-based composite was constructed by a one-step hydrothermal method,and Bi was encapsulated in ligninderived nitrogen-doped porous carbon(Bi@LNPC)after carbonization.The obtained Bi nanoparticles could effectively adapt to the strain and shorten the diffusion distance of Na^(+).In addition,porous carbon skeleton provides a rigid conductive network for electronic transportation.Therefore,the assembled sodium-ion half-cell with Bi@LNPC anode shows ultra-high-rate capability.When the current density was enhanced from 0.1 to 50 A·g^(-1),the specific capacity decreased slightly from 351.5 to 342.8 mAh·g^(-1).Even at an extremely high current density of 200 A·g^(-1),it retains 81.3%capacity retention when compared to a current density of 1 A·g^(-1).The SIHCs assembled by Bi@LNPC show a high energy density of 63 Wh·kg^(-1).This work provides an effective method for developing high-rate Bi anode materials for sodium-ion hybrid capacitors(SIHCs)and sodium-ion batteries(SIBs).展开更多
Transition metal-catalyzed asymmetric transfer hydrogenation has been proven to be a powerful approach for the synthesis of chiral alcohols.Herein,a highly efficient and enantioselective transfer hydrogenation of dibe...Transition metal-catalyzed asymmetric transfer hydrogenation has been proven to be a powerful approach for the synthesis of chiral alcohols.Herein,a highly efficient and enantioselective transfer hydrogenation of dibenzoheptaheterocyclic ketones catalyzed by an arene-tethered TsDPEN-based Rh(ll)catalyst has been successfully developed,and a variety of dibenzoheptaheterocyclic ketones were reduced by a 1/1 mixture of formic acid and DBU(1,8-diazabicyclo[5.4.0]undec-7-ene)with high yields and enantioselectivities.With this method,the asymmetric reduction of 7,8-difluorodibenzo[b,e]thiepin-11(6H)-one has been realized,providing the key intermediate of baloxavir marboxil with>99% yield and>99% ee at a substrate/catalyst molar ratio of 1000.展开更多
Carbonized metallic organic frameworks(CMOF)have been attracting attention in microwave absorption(MA)research area because of their diverse structures,tunable compositions,and rich porosity.Herein,structure regulatio...Carbonized metallic organic frameworks(CMOF)have been attracting attention in microwave absorption(MA)research area because of their diverse structures,tunable compositions,and rich porosity.Herein,structure regulation on metal clusters in CMOF is achieved by tuning the interaction strength between metals and ligands to enhance microwave absorption performance.Due to relatively weak interaction among copper cations and ligands,copper nanoclusters(CuNC)can be uniformly formed and embedded within the cobalt/zinc(Co/Zn)CMOF.Firstly,copper cations are added to the Co/Zn bimetallic zeolitic imidazolate frameworks(ZIFs).Secondly,the CMOF composite particles with CuNCs(CuNCs/CoZn-CMOF)were developed by a pyrolysis process.The CuNCs/CoZn-CMOF with an appropriate amount of CuNCs can harmonize both dielectric and magnetic losses.As a result,the minimum reflection loss(RLmin)reaches–45.1 dB at a matching thickness of 2.30 mm and the effective absorption bandwidth(EAB)is 8.80 GHz at a thickness of 3.10 mm.The broadband response to electromagnetic waves is attributed to interfacial polarization at CuNCs surface and heterogeneous interfaces,impedance matching and multiple scattering of electromagnetic waves.This study provides a feasible method to develop CMOF microwave absorption materials with high EAB values.展开更多
For practicable elastomeric polyethylene,achieving high catalyst thermal stability and activity,along with precise control of polymer properties such as branching density,molecular weights,and distribution,is crucial ...For practicable elastomeric polyethylene,achieving high catalyst thermal stability and activity,along with precise control of polymer properties such as branching density,molecular weights,and distribution,is crucial but challenging.In this study,two sets of symmetricalα-diimine nickel complexes,each comprising four nickel bromide or chloride complexes,were synthesized and investigated their performance for ethylene polymerization under various reaction conditions.Upon activation with either Et2AlCl or MMAO cocatalysts,these complexes displayed not only high activity but also generated high molecular weight polyethylenes with controlled polydispersity and a substantial number of branches.The catalyst with the least steric hindrance displayed the remarkable high activity(up to 1.2×10^(7) g·mol^(-1)·h^(-1)).Notably,nickel bromides demonstrated higher activity compared to their chloride counterparts.The investigation into the effect of reaction temperature on catalytic performance revealed that NiBrMe-MMAO system displayed high thermal stability(activity up to 2.51×10^(6) g·mol^(-1)·h^(-1) at 100℃)and consistently yielded high polymer molecular weights with narrow polydispersity over a broad temperature range of 30-100℃.Of significant note,mechanical analysis of the resulting polyethylene demonstrated excellent ultimate tensile strength and high strain at break.Particularly,the polyethylene sample prepared at 100℃exhibited ultimate tensile strength up to 10 MPa with 1863%maximum strain at break and a strain recovery of up to 54.9%after ten cycles at a fixed strain of 300%,indicating excellent material properties of prepared thermoplastic polyethylene elastomers(TPE).展开更多
基金supported by National Key Research&Development Program of China (2022YFA1506200)the National Natural Science Foundations of China (22078007, 21627813, 21706009,22002085)+3 种基金Guangdong Basic and Applied Basic Research Foundation (2020A1515110832)the Fundamental Research Funds for the Central Universities (buctrc201921, JD2223)Innovative Achievement Commercialization Service-Platform of Industrial CatalysisChemistry and Chemical Engineering Guangdong Laboratory for a startup funding support(2111001)
文摘Bimetallic nanoparticles exhibit a synergistic effect that critically depends on their surface composition,but such promotion mechanisms become vague with varying surface compositions.Here,alumina supported Ag@Pd core–shell and PdAg alloy structure with controlled size and surface compositions were prepared to demonstrate synergetic mechanisms,particularly,ligand and strain effects on activity and ethylene selectivity for acetylene hydrogenation.The performance evaluation indicates that Ag@Pd catalysts with well-controlled Pd-shell thickness can effectively lower apparent activation energy and improve ethylene selectivity.Hydrogenation activity increases from 0.019 to 0.062 s^(-1) with decreasing Pd-shell thickness under mild conditions,which is 3–6 times higher than their alloyed and monometallic counterparts.Combined characterizations and density functional theory are conducted to reveal such shell-thickness-dependent performance.The ligand effect arising from Ag alloying in the interface of Ag@Pd2ML observes the strongest binding of acetylene,but it diminished sharply and the strain effect gets more prevailing with increasing shell thickness.The competition of ethylene desorption and deephydrogenation were also investigated to understand the selectivity governing factors,and the selectivity descriptor(0.5BE(C_(2)H_(4))–BE(H))was built to match the contribution of ligand and strain effect on the different surfaces of Pd-Ag bimetallic NPs.The exploration of synergetic mechanisms among bimetallic NPs with varied structure and surface compositions in this work can help us to deepen the understanding catalyst structure–activity relationship and provide a feasible way to optimize the overall catalytic performance.
基金the financial support from the National Natural Science Foundation of China(22108044,22208061)the Research and Development Program in Key Fields of Guangdong Province(2020B1111380002)+1 种基金the Basic Research and Applicable Basic Research in Guangzhou City(202201010290)the financial support from the Guangdong Provincial Key Laboratory of Plant Resources Biorefinery(2021GDKLPRB07)。
文摘Amorphous carbons are promising anodes for high-rate potassium-ion batteries.Most low-temperature annealed amorphous carbons display unsatisfactory capacities.Heteroatom-induced defect engineering of amorphous carbons could enhance their reversible capacities.Nevertheless,most lignocellulose biomasses lack heteroatoms,making it a challenge to design highly heteroatom-doped carbons(>10 at%).Herein,we report a new preparation strategy for amorphous carbon anodes.Nitrogen/sulfur co-doped lignin-derived porous carbons(NSLPC)with ultra-high nitrogen doping levels(21.6 at%of N and 0.8 at%of S)from renewable lignin biomacromolecule precursors were prepared through a supramolecule-mediated pyrolysis strategy.This supermolecule/lignin composite decomposes forming a covalently bonded graphitic carbon/amorphous carbon intermediate product,which induces the formation of high heteroatom doping in the obtained NSLPC.This unique pyrolysis chemistry and high heteroatom doping of NSLPC enable abundant defective active sites for the adsorption of K+and improved kinetics.The NSLPC anode delivered a high reversible capacity of 419 mAh g^(-1)and superior cycling stability(capacity retention of 96.6%at 1 A g^(-1)for 1000 cycles).Potassiumion hybrid capacitors assembled by NSLPC anode exhibited excellent cycling stability(91%capacity retention for 2000 cycles)and a high energy density of 71 Wh kg^(-1)at a power density of 92 W kg^(-1).
基金supported by the National Natural Science Foundation of China(22278090,21978055)Natural Science Foundation of Guangdong Province,China(2022A1515012088)the Science and Technology Planning Project of Guangdong Province,China(2022A0505030073,2022A0505030013).
文摘Ce-encapsulated Beta zeolite was synthesized by a one-pot hydrothermal method with citric acid complexing Ce in the absence of Na species.Additional citric acid can effectively prevent the deposition of Ce species during the hydrothermal synthesis of zeolites,leading to uniform distribution of Ce cluster in the framework of Beta zeolites.Moreover,the sodium-free synthesis system resulted that the Brønsted acid sites were mainly located on the straight channels and external surface of Beta zeolites,improving the utilization of Brønsted acid sites.In addition,Ce encapsulated Beta zeolites showed enhanced activity and robust stability in the alkylation of benzene with 1-dodecene based on the synergistic effect between Ce species and Brønsted acid sites,which pave the way for its practical application in the production of alkylbenzene.
基金financially supported by the 2022 Special Fund Project for Science and Technology Innovation Strategy of Guangdong Province(STKJ202209077 and STKJ202209083)the Guangdong Province Universities and Colleges Pearl River Scholar Funded Scheme 2019(GDUPS2019)the City University of Hong Kong Strategic Research Grant(SRG)(7005505)。
文摘There have been reports about Fe ions boosting oxygen evolution reaction(OER)activity of Ni-based catalysts in alkaline conditions,while the origin and reason for the enhancement remains elusive.Herein,we attempt to identify the activity improvement and discover that Ni sites act as a host to attract Fe(Ⅲ)to form Fe(Ni)(Ⅲ)binary centres,which serve as the dynamic sites to promote OER activity and stability by cyclical formation of intermediates(Fe(Ⅲ)→Fe(Ni)(Ⅲ)→Fe(Ni)-OH→Fe(Ni)-O→Fe(Ni)OOH→Fe(Ⅲ))at the electrode/electrolyte interface to emit O_(2).Additionally,some ions(Co(Ⅱ),Ni(Ⅱ),and Cr(Ⅲ))can also be the active sites to catalyze the OER process on a variety of electrodes.The Fe(Ⅲ)-catalyzed overall water-splitting electrolyzer comprising bare Ni foam as the anode and Pt/Ni-Mo as the cathode demonstrates robust stability for 1600 h at 1000 mA cm^(-2)@~1.75 V.The results provide insights into the ioncatalyzed effects boosting OER performance.
基金supported by the State Key Laboratory of Catalytic Materials and Reaction Engineering(RIPP,SINOPEC)the National Natural Science Foundation of China(Nos.21878216,22005215)+1 种基金Hebei Province Innovation Ability Promotion Project(No.20312201D)the National Key Research and Development Program of China(No.2019YFE0118800)。
文摘The lithiated covalent organic framework(named TpPa-SO_(3) Li),which was prepared by a mild chemical lithiation strategy,was introduced in poly(ethylene oxide)(PEO)to produce the composite polymer electrolytes(CPEs).Li-ion can transfer along the PEO chain or across the layer of TpPa-SO_(3) Li within the nanochannels,resulting in a high Li-ion conductivity of3.01×10^(-4)S/cm at 60℃.When the CPE with 0.75 wt.%TpPa-SO_(3) Li was used in the LiFePO_(4)‖Li solid-state battery,the cell delivered a stable capacity of 125 mA·h/g after 250 cycles at 0.5 C,60℃.In comparison,the cell using the CPE without TpPa-SO_(3) Li exhibited a capacity of only 118 mA·h/g.
基金supported by the National Natural Science Foundation of China (No. 21878226, No. U20A20153)the Chemistry and Chemical Engineering Guangdong Laboratory (Grant No. 1912011)。
文摘As one of the most common cathode materials for aqueous zinc-ion batteries(AZIBs),manganese oxides have the advantages of abundant reserves,low cost,and low toxicity.However,the electrochemical mechanism at the cathode of aqueous zinc-manganese batteries(AZMBs) is complicated due to different electrode materials,electrolytes and working conditions.These complicated mechanisms severely limit the research progress of AZMBs system and the design of cells with better performance.Hence,the mechanism of AZMBs currently recognized by most researchers according to the classification of the main ions involved in the faradaic reaction is introduced in the review.Then a series of reasons that affect the electrochemical behavior of the battery are summarized.Finally,the failure mechanisms of AZMBs over prolonged cycling are discussed,and the current insufficient research areas of the system are explained,along with the direction of further research being prospected.
基金Natural Science Foundation of China,Grant/Award Number:22108042Guangzhou(202201020147)。
文摘BiVO_(4)is one of the most promising photoanode materials for photoelectrochemical(PEC)solar energy conversion,but it still suffers from poor photocurrent density due to insufficient light‐harvesting efficiency(LHE),weak photogenerated charge separation efficiency(Φ_(Sep)),and low water oxidation efficiency(Φ_(OX)).Herein,we tackle these challenges of the BiVO_(4)photoanodes using systematic engineering,including catalysis engineering,bandgap engineering,and morphology engineering.In particular,we deposit a NiCoO_(x)layer onto the BiVO_(4)photoanode as the oxygen evolution catalyst to enhance theΦ_(OX)of Fe‐g‐C_(3)N_(4)/BiVO_(4)for PEC water oxidation,and incorporate Fe‐doped graphite‐phase C_(3)N_(4)(Fe‐g‐C_(3)N_(4))into the BiVO_(4)photoanode to optimize the bandgap and surface areas to subsequently expand the light absorption range of the photoanode from 530 to 690 nm,increase the LHE andΦ_(Sep),and further improve the oxygen evolution reaction activity of the NiCoO_(x)catalytic layer.Consequently,the maximum photocurrent density of the as‐prepared NiCoO_(x)/Fe‐g‐C_(3)N_(4)/BiVO_(4)is remarkably boosted from 4.6 to 7.4 mA cm^(−2).This work suggests that the proposed systematic engineering strategy is exceptionally promising for improving LHE,Φ_(Sep),andΦ_(OX)of BiVO_(4)‐based photoanodes,which will substantially benefit the design,preparation,and large‐scale application of next‐generation high‐performance photoanodes.
基金supported financially by the National Natural Science Foundation of China(Grant Nos.91961125 and 21905019)“Key Program for International S&T Cooperation Projects of China”from the Ministry of Science and Technology of China(Grant No.2018YFE0124600)+2 种基金“the Fundamental Research Funds for the Central Universities”(Grant No.2018JBZ107)the Chemistry and Chemical Engineering Guangdong Laboratory(Grant No.1932004)support from the“Excellent One Hundred”project of Beijing Jiaotong University。
文摘Up to now,three kinds of ion-storage mechanisms are summarized towards anode materials in lithium/sodium-ion batteries,but they have low capacity and poor cyclic performance.Therefore,it is necessary to develop a new approach to optimize ion storage.Herein,we report an adsorption/desorption storage route through engineering electronic structure of cation-deficient Ti_(1-x)O_(2)nanosheets.Ti_(1-x)O_(2)nanosheets indeed exhibit higher capacity(332.1 mA h g^(-1)vs.137.7 mA h g^(-1)for LIBs,195.7 mA h g^(-1)vs.111 mA h g^(-1)for SIBs),and more stable cyclic performance(296 mA h g^(-1)vs.99 mA h g^(-1)for LIBs,178.1 mA h g^(-1)vs.80.2 mA h g^(-1)for SIBs after 100 cycles)at 0.1 A g^(-1)than TiO_(2)nanosheets.Kinetics analysis and density functional theory(DFT)calculations reveal that electronic structures of vacancy within Ti_(1-x)O_(2) nanosheets encourage a novel adsorption-desorption storage route.These results highlight the benefits of the engineered electronic structures within electrode material and implement novel ion-storage mechanism towards broad energy storage applications.
基金the financial support from the National Natural Science Foundation of China (22108044)the 111 Project (B20088)+3 种基金the Fundamental Research Funds for the Central Universities (2572022DJ02)the Research and Development Program in Key Fields of Guangdong Province (2020B1111380002)the Basic Research and Applicable Basic Research in Guangzhou City (202201010290)the Guangdong Provincial Key Laboratory of Plant Resources Biorefinery (2021GDKLPRB07)。
文摘Zinc ion hybrid capacitors(ZIHCs), which integrate the features of the high power of supercapacitors and the high energy of zinc ion batteries, are promising competitors in future electrochemical energy storage applications. Carbon-based materials are deemed the competitive candidates for cathodes of ZIHC due to their cost-effectiveness, high electronic conductivity, chemical inertness, controllable surface states, and tunable pore architectures. In recent years, great research efforts have been devoted to further improving the energy density and cycling stability of ZIHCs. Reasonable modification and optimization of carbon-based materials offer a remedy for these challenges. In this review, the structural design, and electrochemical properties of carbon-based cathode materials with different dimensions, as well as the selection of compatible, robust current collectors and separators for ZIHCs are discussed. The challenges and prospects of ZIHCs are showcased to guide the innovative development of carbon-based cathode materials and the development of novel ZIHCs.
基金supported by the National Natural Science Foundation of China(No.22108043)Natural Science Foundation of Guangdong Province,China(No.2023A1515012711).
文摘Cobalt-rich perovskite oxides play a paramount role in catalyzing oxygen evolution reaction(OER)on account of their acceptable intrinsic activity but are still challenging due to the high costs and undesired stability.In response to the defects,herein,the Mg-incorporated perovskite cobaltite SrCo_(0.6)Fe_(0.3M)g_(0.1)O_(3-δ)(SCFM-0.1)is proposed as a novel earth-abundant and durable OER electrocatalyst.A well-consolidated cubic-symmetry structure and more active oxygen intermediates are enabled upon Mg substitution.Hence,the optimized SCFM-0.1 perovskite oxide achieves prominent OER electrocatalytic performance,that is,a low overpotential of only 320 mV at 10 mA cm^(-2),a small Tafel slope of 65 mV dec^(-1),as well as an outstanding durability within 20 h,substantially outperforming that of the pristine SrCo_(0.7)Fe_(0.3)O_(3-δ)and benchmark Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3-δ)and IrO_(2) catalysts.The strong pHdependent behavior associated with lattice oxygen activation mechanism for SCFM-0.1 catalyst is also confirmed.This work paves a unique avenue to develop cost-effective and robust perovskite cobaltites for efficient OER electrocatalysis.
基金the Science and Technology Project of Maoming(China)(200203094555139)for financial support。
文摘The development of polyoxometalates for olefin oxidation is critical to achieving the green chemical process of the C5 fraction further processing.Di-lacunary silicotungstic anions were easily obtained by continuously adjusting the p H instead of the traditional step-by-step method,which exhibited excellent performance in the catalytic oxidation of cyclopentene(CPE)to aldehydes or alcohols.The 93.69%CPE conversion and 97.15%total product selectivity(41.38%for glutaraldehyde(GA)and 55.77%for 1,2-cyclopentanediol(1,2-diol)were achieved by using H_(2)O_(2)as the oxidant and acetonitrile as the solvent.Through complementary characterization,it was found that the optimized di-lacunary silicotungstic polyoxometalate retained a complete Keggin structure,and exhibited better catalytic activity and stability than the mono-lacunary or saturated silicodecatungstate because it exposed more catalytic active centers.Furthermore,in situ FT-IR spectra was utilized to monitor the reaction process,revealing the formation of the active species W(O_(2))on the di-lacunary silicotungstic polyoxometalate and the intermediate epoxycyclopentane during the catalytic oxidation of cyclopentene.
基金supported by the National Natural Science Foundation of China (21978055, 22278090)Natural Science Foundation of Guangdong Province, China (2022A1515012088)+2 种基金the Science and Technology Planning Project of Guangdong Province, China (22A0505050073, 2022A0505030013)the Guangdong Provincial Key Laboratory of Plant Resources Biorefinery, China (2021GDKLPRB10)the "High-level Talents Program" of the Pearl River, China (2017GC010080)。
文摘Novel organo-inorganic hybrid materials(MTW-x-SO_(3)H) have been fabricated by immobilizing 3-mercap topropyltriethoxysilane onto mesopore MTW zeolites, which is treated via a simple oxidation process with hydrogen peroxide as the oxidant to transform sulfhydryl group into sulfonic acid group. The organic sulfhydryl groups are covalently bonded to the external surface of MTW zeolites through the condensation between siloxane arising from organic fragments with silanol groups on the surface of MTW zeolites, the hybrids contain sulfonic acid group within the external surface of MTW zeolites and an opened mesoporous system in the matrix of MTW zeolites, which provide enough accessible Brùnsted acid sites for the alkylation between phenol with tert-butyl alcohol. Through this methodology it's possible to prepare multifunctional materials where the plenty of mesopores are benefit for the introduction of larger numbers of sulfonic acid groups that contributes to activity during reactions, resulting in high activity(>55%) of MTW-4-SO_(3)H and desired selectivity(>56%) of 2-TBP(2-tert-butyl phenol) in the alkylation between phenol with tert-butyl alcohol.
基金supported by the National Natural Science Foundation of China(No.22002174,21802164,21902180 and U1832148)Natural Science Foundation of Hubei Province of China(2018CFA009)+1 种基金Key Research Program of Frontier Sciences,CAS(No.QYZDB-SSW-SLH026)China Postdoctoral Science Foundation(2019M662753)。
文摘Adsorption and separation of C_(4) hydrocarbons are crucial steps in petrochemical processes.Employment of porous materials for enhancing the separation efficiency have paid much attention.Covalent-organic frameworks of diamond-topology,dia-COFs,often exhibit unique structural properties such as interpenetration isomerism and pedal motion.Herein,in order to get a deep insight into the structure-performance correlation of such dia-COFs,a series of dia-COF materials have been proposed and theoretically investigated on the C_(4) separation.It is found that these dia-COFs display an excellent adsorption and separation property towards isobutene with respect to other C_(4) hydrocarbons(i.e.,1,3-butadiene,1-butene,2-cis-butene,2-trans-butene,isobutane and n-butane).What’s more,the correlation between the topology parameters and experimental synthesis feasibility has been established for COF-300(dia-cN),and the unreported COF-300(dia-c3) is predicted to be experimentally feasible synthesized.Our findings not only provide a deep insight into the mechanism of topology characteristics of dia-COFs on C_(4) adsorption and separation properties but also guide the design and synthesis of novel highly-effective porous materials.
基金supported by the Key-Area Research and Development Program of Guangdong Province(grant no.2020B0909-19005)the National Natural Science Foundation of China(grant nos.21975056 and 22179025)+1 种基金The Major and Special Project in the Field of Intelligent Manufacturing of the Universities in Guangdong Province(grant no.2020ZDZX2067)the Natural Science Foundation of Huizhou University(grant no.HZU202004).
文摘With advantages of low costs and high energy density,Li–S batteries are considered as one of the most promising energy storage devices.However,Li_(2)S_(2) with a high dissociation energy and insulative properties is hard to convert into Li_(2)S,resulting in underutilization of sulfur capacity.Herein,Co-Mo_(2)C@C yolk–shell spheres as nanoreactors were designed to confront this challenge rationally.The Co-Mo_(2)C@C-induced Li_(2)S_(1/2) nucleation and growth in the three-dimensional process and the cathode produced more Li_(2)S after full discharge.Experimental studies and theoretical calculations reveal that the conversion barrier from Li_(2)S_(2) into Li_(2)S was lowered while the diffusion of lithium ions and electron transfer accelerated when using the Co-Mo_(2)C@C catalyst.Based on the above advantages,the Co-Mo_(2)C@C/S cathode exhibits a high reversible capacity and excellent cyclic stability,such as an initial specific capacity of 1200 mAh g^(−1) at 0.1 C with 709 mAh g^(−1) at 1.0 C after 1000 cycles with a low capacity fading rate of 0.04%per cycle.Even at high densities of 3.0 C and 5.0 C,the specific capacities are 647.6 and 557.7 mAh g^(−1) after 400 cycles,respectively.Impressively,it also shows ca.770 and 900 mAh g^(−1) at 0.2 C after 50 cycles with high sulfur loadings of 4.2 and 5.1 mg cm−2,respectively.The present work may provide new insights into the design of nanoreactors to promote Li_(2)S_(1/2) growth in a three-dimensional process and accelerate conversion from solid Li_(2)S_(2) to solid Li_(2)S in high performance Li–S batteries.
基金financially supported by National Natural Science Foundation of China(22172077,T2322013)the Scientific Research Foundation of Chemistry and Chemical Engineering Guangdong Laboratory(2011001)the support by the National Research Foundation of Korea(NRF)funded by the Ministry of Science and ICT(2018M3D1A1058624,2019R1A2C3010479)。
基金supported by the National Natural Science Foundation of China (52102225 and 51874104)the Start-up Research Grant of Guangdong University of Technology,China (220413729)。
文摘非化学计量微米氧化硅(SiO_(x))由于其高理论容量和低成本,有望成为锂离子电池石墨负极材料的替代品.然而,SiO_(x)的实际应用仍然受到其较差的固有导电性和循环过程中明显的体积变化的阻碍.在本工作中,为了同时解决这些问题,我们使用可规模化的溶剂热和热还原方法制备了具有TiO_(1-y)Ny-C涂层的SiO_(x)基负极材料(SiO_(x)@TiON-C).我们通过系统性研究发现,TiO_(1-y)Ny-C涂层可以适应SiO_(x)循环过程中大的体积变化且有效提高其导电性.因此,SiO_(x)@TiON-C负极具有突出的储锂性能.具体而言,SiO_(x)@TiON-C负极可以在500 mA g^(-1)的电流密度下循环500圈后仍保持750.2 mA h g^(-1)的优异可逆容量,75.1%的初始库仑效率和优异的倍率性能.这项工作为促进下一代锂离子电池微米SiO_(x)基负极材料的实际商业化提供了一种很有前途的方法.
基金financially supported by the National Natural Science Foundation of China(No.22108044)the Research and Development Program in Key Fields of Guangdong Province(No.2020B1111380002)+1 种基金the Basic Research and Applicable Basic Research in Guangzhou City(No.202201010290)the financial support from the Guangdong Provincial Key Laboratory of Plant Resources Biorefinery(No.2021GDKLPRB07)。
文摘Bismuth(Bi),as an alloy-based anode material,has attracted much atte ntion in the developme nt of sodiumion hybrid capacitors(SIHCs)due to its high theoretical capacity.However,the volume expansion of the Bi-based anode during the sodiation/desodiation process results in limited rate capability.In the present work,a porous Bi-based composite was constructed by a one-step hydrothermal method,and Bi was encapsulated in ligninderived nitrogen-doped porous carbon(Bi@LNPC)after carbonization.The obtained Bi nanoparticles could effectively adapt to the strain and shorten the diffusion distance of Na^(+).In addition,porous carbon skeleton provides a rigid conductive network for electronic transportation.Therefore,the assembled sodium-ion half-cell with Bi@LNPC anode shows ultra-high-rate capability.When the current density was enhanced from 0.1 to 50 A·g^(-1),the specific capacity decreased slightly from 351.5 to 342.8 mAh·g^(-1).Even at an extremely high current density of 200 A·g^(-1),it retains 81.3%capacity retention when compared to a current density of 1 A·g^(-1).The SIHCs assembled by Bi@LNPC show a high energy density of 63 Wh·kg^(-1).This work provides an effective method for developing high-rate Bi anode materials for sodium-ion hybrid capacitors(SIHCs)and sodium-ion batteries(SIBs).
基金the Southern University of Science and Technology(start-up fund),Shenzhen Science and Technology Innovation Committee(No.KQTD20150717103157174)Stable Support Plan Program of Shenzhen Natural Science Fund(Program Contract No.20200925161222002)+4 种基金Key-Area Research and DevelopmentPt rogramofGuangdong Province((No.2020B010188001)Innovative Team of Universities in Guangdong Province(No.2020KCXTD016)National Natural Science Foundation of China(No.21991113)the National Natural Science Foundation of China(No.22171129)Shenzhen Science and Technology Innovation Committee(JCYJ20210324104202007)for financial support.
文摘Transition metal-catalyzed asymmetric transfer hydrogenation has been proven to be a powerful approach for the synthesis of chiral alcohols.Herein,a highly efficient and enantioselective transfer hydrogenation of dibenzoheptaheterocyclic ketones catalyzed by an arene-tethered TsDPEN-based Rh(ll)catalyst has been successfully developed,and a variety of dibenzoheptaheterocyclic ketones were reduced by a 1/1 mixture of formic acid and DBU(1,8-diazabicyclo[5.4.0]undec-7-ene)with high yields and enantioselectivities.With this method,the asymmetric reduction of 7,8-difluorodibenzo[b,e]thiepin-11(6H)-one has been realized,providing the key intermediate of baloxavir marboxil with>99% yield and>99% ee at a substrate/catalyst molar ratio of 1000.
基金We thank the National Natural Science Foundation of China(No.52173264)for financial support。
文摘Carbonized metallic organic frameworks(CMOF)have been attracting attention in microwave absorption(MA)research area because of their diverse structures,tunable compositions,and rich porosity.Herein,structure regulation on metal clusters in CMOF is achieved by tuning the interaction strength between metals and ligands to enhance microwave absorption performance.Due to relatively weak interaction among copper cations and ligands,copper nanoclusters(CuNC)can be uniformly formed and embedded within the cobalt/zinc(Co/Zn)CMOF.Firstly,copper cations are added to the Co/Zn bimetallic zeolitic imidazolate frameworks(ZIFs).Secondly,the CMOF composite particles with CuNCs(CuNCs/CoZn-CMOF)were developed by a pyrolysis process.The CuNCs/CoZn-CMOF with an appropriate amount of CuNCs can harmonize both dielectric and magnetic losses.As a result,the minimum reflection loss(RLmin)reaches–45.1 dB at a matching thickness of 2.30 mm and the effective absorption bandwidth(EAB)is 8.80 GHz at a thickness of 3.10 mm.The broadband response to electromagnetic waves is attributed to interfacial polarization at CuNCs surface and heterogeneous interfaces,impedance matching and multiple scattering of electromagnetic waves.This study provides a feasible method to develop CMOF microwave absorption materials with high EAB values.
基金This work was financially supported by the Chemistry and Chemical Engineering Guangdong Laboratory(Nos.2111018 and 2132012)Q.M.would like to express gratitude towards the Foreign Youth Talent Program(No.QN2022030008L)for their support.
文摘For practicable elastomeric polyethylene,achieving high catalyst thermal stability and activity,along with precise control of polymer properties such as branching density,molecular weights,and distribution,is crucial but challenging.In this study,two sets of symmetricalα-diimine nickel complexes,each comprising four nickel bromide or chloride complexes,were synthesized and investigated their performance for ethylene polymerization under various reaction conditions.Upon activation with either Et2AlCl or MMAO cocatalysts,these complexes displayed not only high activity but also generated high molecular weight polyethylenes with controlled polydispersity and a substantial number of branches.The catalyst with the least steric hindrance displayed the remarkable high activity(up to 1.2×10^(7) g·mol^(-1)·h^(-1)).Notably,nickel bromides demonstrated higher activity compared to their chloride counterparts.The investigation into the effect of reaction temperature on catalytic performance revealed that NiBrMe-MMAO system displayed high thermal stability(activity up to 2.51×10^(6) g·mol^(-1)·h^(-1) at 100℃)and consistently yielded high polymer molecular weights with narrow polydispersity over a broad temperature range of 30-100℃.Of significant note,mechanical analysis of the resulting polyethylene demonstrated excellent ultimate tensile strength and high strain at break.Particularly,the polyethylene sample prepared at 100℃exhibited ultimate tensile strength up to 10 MPa with 1863%maximum strain at break and a strain recovery of up to 54.9%after ten cycles at a fixed strain of 300%,indicating excellent material properties of prepared thermoplastic polyethylene elastomers(TPE).