The high-efficiency conversion of biomass resources to biofuels has attracted widespread attention, and the active sites and synergistic effect of catalysts significantly impact their surface arrangement and electroni...The high-efficiency conversion of biomass resources to biofuels has attracted widespread attention, and the active sites and synergistic effect of catalysts significantly impact their surface arrangement and electronic structure. Here, a nickel-based transition metal carbide catalyst(Ni/TMC) with high Lewis acidity was prepared by self-assembly of transition metal carbide(TMC) and nickel, which exhibited excellent performance on synergistic hydrogenation and hydrogenolysis of 5-hydroxymethylfurfural(HMF) into liquid biofuel 2,5-dimethylfuran(DMF).Notably, Ni/WC with the highest Lewis acidity(4728.3 μmol g^(-1)) can achieve 100% conversion of HMF to 97.6% yield of DMF, with a turnover frequency of up to 46.5 h^(-1). The characterization results demonstrate that the rich Lewis acid sites yielded by the synergistic effect between Ni species and TMC are beneficial for the C=O hydrogenation and C–O cleavage, thereby accelerating the process of hydrodeoxygenation(HDO). Besides, a kinetic model for the HDO of HMF to DMF process has been established based on the experimental results, which elucidated a significant correlation between the measured and the predicted data(R^(2)> 0.97). Corresponding to the adsorption configuration of Ni/WC and substrate determined by in-situ FTIR characterization, this study provides a novel insight into the selective conversion of HMF process for functional biofuel and bio-chemicals.展开更多
Direct electrolysis of seawater offers a transformative technology for sustainable hydrogen production,circumventing the constraint of freshwater scarcity.However,the serious electrode corrosion and competitive chlori...Direct electrolysis of seawater offers a transformative technology for sustainable hydrogen production,circumventing the constraint of freshwater scarcity.However,the serious electrode corrosion and competitive chloride oxidation reactions make oxygen evolution reaction(OER)in seawater extremely challenging.Herein,the low-cost and scalable CoFe layered double hydroxides with Cl^(-)intercalation and decorated with Ce(OH)_(3)(named as CoFe-Cl^(-)/Ce(OH)_(3))catalyst is synthesized via rapid electrodeposition under ambient conditions,which is quickly reconstructed into a CeO_(2)decorated and Cl^(-)intercalated CoFeOOH(CoFeOOH-Cl^(-)/CeO_(2))during OER.Theoretical investigation reveals that Cl^(-)intercalation weakens the adsorption ability of Cl^(-)on Co/Fe atoms and hinders unfavorable coupling with chloride,thereby preventing the chlorine corrosion process and enhancing catalytic stability and activity.The CeO_(2)with hard Lewis acidity preferentially binds to OH-with harder Lewis base to ensure the OH-rich microenvironment around catalyst even under high current operating conditions,thus further enhancing stability and improving OER activity.The functionalized CoFe-Cl^(-)/Ce(OH)_(3)delivers 1000 mA cm^(-2)current density at only 329 mV overpotential with excellent stability for 1000 h under alkaline seawater.Electrochemical experiments elucidate the OER catalytic mechanism in which CeO_(2)serves as a co-catalyst for enriching OH-and CoFeOOH-Cl^(-)is the active species.Our work is a substantial step towards achieving massive and sustainable production of hydrogen fuel from immense seawater.展开更多
Since the discovery in 2011,MXenes have become the rising star in the field of two-dimensional materials.Benefiting from the metallic-level conductivity,large and adjustable gallery spacing,low ion diffusion barrier,r...Since the discovery in 2011,MXenes have become the rising star in the field of two-dimensional materials.Benefiting from the metallic-level conductivity,large and adjustable gallery spacing,low ion diffusion barrier,rich surface chemistry,superior mechanical strength,MXenes exhibit great application prospects in energy storage and conversion,sensors,optoelectronics,electromagnetic interference shielding and biomedicine.Nevertheless,two issues seriously deteriorate the further development of MXenes.One is the high experimental risk of common preparation methods such as HF etching,and the other is the difficulty in obtaining MXenes with controllable surface groups.Recently,Lewis acidic etching,as a brand-new preparation strategy for MXenes,has attracted intensive attention due to its high safety and the ability to endow MXenes with uniform terminations.However,a comprehensive review of Lewis acidic etching method has not been reported yet.Herein,we first introduce the Lewis acidic etching from the following four aspects:etching mechanism,terminations regulation,in-situ formed metals and delamination of multi-layered MXenes.Further,the applications of MXenes and MXene-based hybrids obtained by Lewis acidic etching route in energy storage and conversion,sensors and microwave absorption are carefully summarized.Finally,some challenges and opportunities of Lewis acidic etching strategy are also presented.展开更多
Carbon materials have shown remarkable usefulness in facilitating the performance of insulating sulfur cathode for lithium–sulfur batteries owing to their excellent conductivity and porous structure. However,the anxi...Carbon materials have shown remarkable usefulness in facilitating the performance of insulating sulfur cathode for lithium–sulfur batteries owing to their excellent conductivity and porous structure. However,the anxiety is the poor affinity toward polar polysulfides due to the intrinsic nonpolar surface of carbon.Herein, we report a direct pyrolysis of the mixture urea and boric acid to synthesize B/N–codoped hierarchically porous carbon nanosheets(B–N–CSs) as efficient sulfur host for lithium–sulfur battery. The graphene–like B–N–CSs provides high specific surface area and porous structure with abundant micropores(1.1 nm) and low–range mesopores(2.3 nm), thereby constraining the sulfur active materials within the pores. More importantly, the codoped B/N elements can further enhance the polysulfide confinement through strong Li–N and B–S interaction based on the Lewis acid–base theory. These structural superiorities significantly suppress the shuttle effect by both physical confinement and chemical interaction, and promote the redox kinetics of polysulfide conversion. When evaluated as the cathode host, the S/B–N–CSs composite displays the excellent performance with a high reversible capacity up to 772 m A h g–1 at 0.5 C and a low fading rate of ^0.09% per cycle averaged upon 500 cycles. In particular, remarkable stability with a high capacity retention of 87.1% can be realized when augmenting the sulfur loading in the cathode up to 4.6 mg cm^(-2).展开更多
An experimental investigation was conducted to understand the roles of the Br？nsted acid H2SO4 and Lewis acid Al2（SO4）3 in methyl levulinate（ML） production from biomass carbohydrates, including glucose,fructose a...An experimental investigation was conducted to understand the roles of the Br？nsted acid H2SO4 and Lewis acid Al2（SO4）3 in methyl levulinate（ML） production from biomass carbohydrates, including glucose,fructose and cellulose. The product distributions with different catalysts revealed that the Lewis acid was responsible for the isomerization of methyl glucoside（MG）, producing a significant amount of the subsequent product 5-methoxymethylfurfural（MMF）, while the Br？nsted acid facilitated the production of ML from MMF. Al2（SO4）3 was efficient for monosaccharide conversion but not for cellulose. Using ball-milled cellulose with Al2（SO4）3 resulted in a desired ML yield within a reasonable reaction time. The significant catalysis performances of two types of acids will guide the design of efficient catalytic processes for the selective conversion of biomass into levulinate esters.展开更多
Novel Lewis acidic ionic liquids containing thionyl cations and chloroaluminate anions were obtained by one-pot synthesis for the first time. Their acidities were determined by acetonitrile probe on IR spectrography. ...Novel Lewis acidic ionic liquids containing thionyl cations and chloroaluminate anions were obtained by one-pot synthesis for the first time. Their acidities were determined by acetonitrile probe on IR spectrography. The ionic liquids were used as catalyst for Friedel-Crafts alkylation of benzene and 1-dodecene. The turnovers of l-dodecene were higher than 99%. Monoalkylbenzene selectivity was 98%, while the 2-substituent product selectivity was 45%.展开更多
The self-aldol condensation of aldehydes was investigated with rare-earth cations stabilized by[Si]Beta zeolites in parallel with bulk rare-earth metal oxides.Good catalytic performance was achieved with all Lewis aci...The self-aldol condensation of aldehydes was investigated with rare-earth cations stabilized by[Si]Beta zeolites in parallel with bulk rare-earth metal oxides.Good catalytic performance was achieved with all Lewis acidic rare-earth cations stabilized by zeolites and yttrium appeared to be the best metal choice.According to the results of several complementary techniques,i.e.,temperature-programmed surface reactions,in situ diffuse reflectance infrared Fourier transform spectroscopy,ultraviolet-visible diffuse reflectance spectroscopy,the reaction pathway and mechanism of the aldehyde self-aldol condensation over Y/Beta catalyst were studied in more detail.Density functional theory calculations revealed that aldol dehydration was the rate-limiting step.The hydroxyl group at the open yttrium site played an important role in stabilizing the transition state of the aldol dimer reducing the energy barrier for its hydration.Lewis acidic Y(OSi)(OH)2 stabilized by zeolites in open configurations were identified as the preferred active sites for the self-aldol condensation of aldehydes.展开更多
Ring-opening copolymerization of CO_(2) and epoxides is a promising way to manufacture high value-added materials.Despite a variety of catalyst systems have been reported,the reaction is still limited by low activity ...Ring-opening copolymerization of CO_(2) and epoxides is a promising way to manufacture high value-added materials.Despite a variety of catalyst systems have been reported,the reaction is still limited by low activity and polymer selectivity.Herein,a strategy of polymerization-enhanced Lewis acidity is reported to construct a series of highly efficient polymeric aluminum porphyrin catalysts(PAPCs).The characterization of the coordination equilibrium constant(K_(eq))showed significantly enhanced Lewis acidity of PAPC(K_(eg)=18.2 L/mol)compared to the monomeric counterpart(K_(eq)=6.4 L/mol),accompanied with increased turnover frequency(TOF)from 136 h^(-1) to 5500 h^(-1).Through detailed regulation of Lewis acidity,the highly Lewis acidic PAPC-OTs displayed a record high TOF of 30,200 h^(-1) with polymer selectivity of up to 99%.展开更多
CeO_(2)-based catalysts are emerging as novel candidates for catalyzing nitrogen reduction reaction(NRR).However, despite the increasing amount of experimental and theoretical research, the design of more efficient ce...CeO_(2)-based catalysts are emerging as novel candidates for catalyzing nitrogen reduction reaction(NRR).However, despite the increasing amount of experimental and theoretical research, the design of more efficient ceria catalysts for NRR remains a challenge due to the poor knowledge of the catalytic mechanism, particularly the nature of the active sites and how they catalyze NRR. Here, using first-principle calculations, we investigated the NRR catalysis process involving adjacent Ce Lewis acid clusters formed on(111),(110), and(100) facets of CeO_(2) as active sites. Our results revealed that the assembled structures of the Ce Lewis acid as active centers after the oxygen vacancies(Ovs) were opened. The exposed Ce sites on CeO_(2)(111), CeO_(2)(110), and CeO_(2)(100) can cause N_(2) to be adsorbed in a ‘‘lying-down" manner, which facilitates the N2 activation and thus leads to much higher NRR activity. Furthermore, from the perspective of electronic structure, we establish two useful descriptors for assessing the NRR activity on ceria with Ovs:The N–N bond strength of the adsorbed N_(2) and the adsorption energy of the *N_(2)H intermediate. This work thus provides direct guidance for the design of more-effective oxide catalysts without the use of scarce metals.展开更多
The azides were reduced to the corresponding amines by two new metal/Lewis acid systems in water or in aqueous EtOH in yields ranging from 80%-95%. The reaction rates were faster in water than in aqueous EtOH in most...The azides were reduced to the corresponding amines by two new metal/Lewis acid systems in water or in aqueous EtOH in yields ranging from 80%-95%. The reaction rates were faster in water than in aqueous EtOH in most cases. All 16 azides with different functional groups were well reduced to the corresponding amines in excellent yields and reaction rates.展开更多
The incorporation of boron into carbon material can significantly enhance its capacity performances.However,the origin of the promotion effect of boron doping on electrochemical performances is still unclear,in part d...The incorporation of boron into carbon material can significantly enhance its capacity performances.However,the origin of the promotion effect of boron doping on electrochemical performances is still unclear,in part due to the inadequate exposure of boron configurations resulting from the complexity of traditional carbon materials.To overcome this issue,herein,a series of boron-doped graphene with highly-exposed boron configurations are prepared by tuning annealing temperature.Then the correlation between boron configurations and the electrochemical performances is investigated.The combination of density-functional theory(DFT)computation and NH3-TPD/Py-FTIR indicates that the BCO_(2)configuration formed on the surface of graphene is easier to accept lone-pair electrons than BC_(2)O and BC_(3)configurations due to the stronger Lewis acidity.Such an electronic structure can effectively reduce the number of unstable electron donors and stabilize the electrochemical interface,which is proved by NMR,and critical for improving the electrochemical performances.Further experiments confirm that the optimized BG800 with the largest amount of BCO_(2)configuration presents ultralow leak current,improved cyclic stability,and better rate performance in SBPBF4/PC.This work would provide an insight into the design of high-performance boron-doped carbon materials towards energy storage.展开更多
Lewis acidic ionic liquids were used to catalyze the reaction of epoxypropane with POCl3. Considering the lower cost and catalytic activities, we concluded that [Et3NH]Cl/AlCl3 was the most attractive ionic liquid fro...Lewis acidic ionic liquids were used to catalyze the reaction of epoxypropane with POCl3. Considering the lower cost and catalytic activities, we concluded that [Et3NH]Cl/AlCl3 was the most attractive ionic liquid from an economical point of view. But it would be easily inactivated because of sensitive to water and air. Moreover, it could not be reused easily because of difficulty recovery in the reaction. However, supporting [Et3NH]Cl/AlCl3 catalyst could resolve above problems. Supporting [Et3NH]Cl/ AlCl3 catalyst could be separated by filter easily and reused 5 times in 98% yield. Furthermore, the catalyst was applicable to other epoxy ether cleaving reactions.展开更多
A substitution reaction of amines with alcohols for N-alkylated amines has been developed using inexpensive AlCl3without any ligand or additive.Either aromatic or aliphatic amines and primary or secondary alcohols per...A substitution reaction of amines with alcohols for N-alkylated amines has been developed using inexpensive AlCl3without any ligand or additive.Either aromatic or aliphatic amines and primary or secondary alcohols perform the AlCl3-mediated reaction smoothly to afford various N-alkylated amines in satisfactory yields.展开更多
Treatment of steroidal sapogenin diosgenin 1 with Lewis acid ethereal trifluoroborane in acetic anhydride at room temperature afforded a new type of pseudosapugenin 23, 26-diacetyl-△22(23)- pseudo-sapogenin 3 and its...Treatment of steroidal sapogenin diosgenin 1 with Lewis acid ethereal trifluoroborane in acetic anhydride at room temperature afforded a new type of pseudosapugenin 23, 26-diacetyl-△22(23)- pseudo-sapogenin 3 and its C-20 isomer 4 in 54% and 19% yield respectively.The possible mechanism was also suggested.展开更多
Metal nanoparticle catalysts, especially gold and its bimetallic nanoparticle catalysts, have been widely used in organic transformations as powerful and green catalysts. The concept of employing two distinct catalyst...Metal nanoparticle catalysts, especially gold and its bimetallic nanoparticle catalysts, have been widely used in organic transformations as powerful and green catalysts. The concept of employing two distinct catalysts in one reaction system, such as in cooperative and synergistic catalysis, is a powerful strategy in homogeneous catalysis. However, the adaption of such a strategy to metal nanoparticle catalysis is still under development. Recently, we have found that cooperative catalytic systems of gold/palladium bimetallic nanoparticles and Lewis acid can be used for the N‐alkylation of primary amides through hydrogen autotransfer reaction between amide and alcohol. Herein, the results of a detailed investigation into the effects of Lewis acids on this hydrogen autotransfer reac‐tion are reported. It was found that the choice of Lewis acid affected not only the reaction pathway leading to the desired product, but also other reaction pathways that produced several intermedi‐ates and by‐products. Weak Lewis acids, such as alkaline‐earth metal triflates, were found to be optimal for the desired N‐alkylation of amides.展开更多
For efficient removal of thiophenic sulfur （S-） compounds from oils, a novel method is proposed here, i.e. one-pot alkylation desulfurization （OADS）, in which oil insoluble chlorinated polymer such as polyvinyl ch...For efficient removal of thiophenic sulfur （S-） compounds from oils, a novel method is proposed here, i.e. one-pot alkylation desulfurization （OADS）, in which oil insoluble chlorinated polymer such as polyvinyl chlo- ride （PVC） is used as the alkylating regent with Lewis acid as catalyst. The aromatic S-compounds are grafted to the polymer through Friedel-Crafts reaction and removed facilely along with the polymer. The OADS mechanism is identified by scanning electron microscope and analyzer with surface area and pore size of the polymer. The influ- ence of some factors on the OADS is studied, e.g. the type and amount of chlorinated polymers and Lewis acids. It is nroved that thionhene and benzothioDhene can be removed efficiently from oil by PVC＋AlCl3 mixture even in the presence of 25% （by mass） of benzene due to the synergetic effects of the adsorptive desulfurization of AlCl3 and the alkylation desulfurization of PVC.展开更多
We report the Lewis acid catalysis of aryldiazonium salts,and their Lewis acidity applications in photogeneration of aryl radicals under additive-,photocatalyst-and transition metal-free conditions.In this visible lig...We report the Lewis acid catalysis of aryldiazonium salts,and their Lewis acidity applications in photogeneration of aryl radicals under additive-,photocatalyst-and transition metal-free conditions.In this visible light-mediated transformation,the Lewis acidic character of aryldiazonium salts enables access to the photoactive charge transfer complex with dichalcogenides.The usefulness and versatility of this new protocol are demonstrated through the chalcogenation of a variety of aryldiazonium salts.展开更多
Chloro(5,10,15,20-tetraphenyl-porphyrinato)-aluminum/tetraethylammonium bromide(Et4NBr)in combination with bulky Lewis acid was used for the copolymerization of CO_2 and cyclohexene oxide(CHO).Bulky Lewis acid having ...Chloro(5,10,15,20-tetraphenyl-porphyrinato)-aluminum/tetraethylammonium bromide(Et4NBr)in combination with bulky Lewis acid was used for the copolymerization of CO_2 and cyclohexene oxide(CHO).Bulky Lewis acid having substituents at the ortho positions of the phenolate ligands,like methylaluminum bis(2,6-di-tert-butyl-4-methylphenolate), significantly shortened the induction period and raised the catalytic activity,the corresponding turnover frequency reached 44.9 h^(-1)in 9 h,which was 23.8% higher than th...展开更多
Herein,a new mechanism involving Lewis acid-oxygen vacancy interfacial synergistic catalysis fo r aniline N,N-diethylation with ethanol was proposed,and the SO4^2-/Ce0.84Zr0.16O2-WO3-ZrO2 catalyst(SCWZ)with both Lewis...Herein,a new mechanism involving Lewis acid-oxygen vacancy interfacial synergistic catalysis fo r aniline N,N-diethylation with ethanol was proposed,and the SO4^2-/Ce0.84Zr0.16O2-WO3-ZrO2 catalyst(SCWZ)with both Lewis acid sites and oxygen vacancies was synthesized by the hydrothermal method,which shows better catalytic activity than the reported solid acidic catalysts.Besides,the SO4^2-/ZrO2(SZ)and SO4^2-/WO3-ZrO2(SWZ)catalysts were also prepared and compared with SCWZ to investigate the synergistic effect of each component.The SO4^2-and WO3 mainly generate Lewis acid by bonding with ZrO2,which is beneficial for the fracture of the N-H bond in aniline.The Ce0.84Zr0.16O2 solid solution mainly plays a vital role in generating the oxygen vacancies as the interface active species,which can participate in stripping-OH from ethanol,then the carbocation will also be released,which only needs1.3805 kcal/mol energy,calculated by density functional theory(DFT),to be input.In comparison,the traditional reaction mechanism needs the Br■nsted acidic sites to promote the protonation of ethanol,then dehydration and subsequent formation of carbocation followed,and 108.6846 kcal/mol energy needs to be input,which is far higher than that of the new mechanism.The apparent activation energy(Ea)over SCWZ was measured by experiment to be 34.09 kJ/mol,which is much lower than that of SWZ(47.10 kJ/mol)and SZ(54.37 kJ/mol),illustrating comparatively preferable kinetics for SCWZ than that of SWZ and SZ.Besides,the conversion of aniline and selectivity to N,N-diethylaniline over SCWZ reach almost 100%and 73%,respectively,The SCWZ can be renewed for 4 times without rapid deactivation,and the longevity of SCWZ is longer than that of SWZ and SZ,as the loaded SO4^2-and tetragonal ZrO2 are stabilized by Ce0.84Zr0.16O2 and WO3,respectively.展开更多
Lewis acidic guanidinium ionic liquid（LAGIL） 2c was used as a novel, efficient and recyclable catalyst for aminolysis of epoxides under solvent-free and room temperature conditions, giving the corresponding β-amino...Lewis acidic guanidinium ionic liquid（LAGIL） 2c was used as a novel, efficient and recyclable catalyst for aminolysis of epoxides under solvent-free and room temperature conditions, giving the corresponding β-amino alcohols with moderate to excellent regioselectivity（up to 91：9） in high yields（up to 97%）. In addition, LAGIL 2c was recycled three times without any loss of catalytic activity and selectivity to the product.展开更多
基金Fundamental Research Foundation of CAF (CAFYBB2022QB001)National Nature Science Foundation of China for Excellent Young Scientists Fund (32222058)。
文摘The high-efficiency conversion of biomass resources to biofuels has attracted widespread attention, and the active sites and synergistic effect of catalysts significantly impact their surface arrangement and electronic structure. Here, a nickel-based transition metal carbide catalyst(Ni/TMC) with high Lewis acidity was prepared by self-assembly of transition metal carbide(TMC) and nickel, which exhibited excellent performance on synergistic hydrogenation and hydrogenolysis of 5-hydroxymethylfurfural(HMF) into liquid biofuel 2,5-dimethylfuran(DMF).Notably, Ni/WC with the highest Lewis acidity(4728.3 μmol g^(-1)) can achieve 100% conversion of HMF to 97.6% yield of DMF, with a turnover frequency of up to 46.5 h^(-1). The characterization results demonstrate that the rich Lewis acid sites yielded by the synergistic effect between Ni species and TMC are beneficial for the C=O hydrogenation and C–O cleavage, thereby accelerating the process of hydrodeoxygenation(HDO). Besides, a kinetic model for the HDO of HMF to DMF process has been established based on the experimental results, which elucidated a significant correlation between the measured and the predicted data(R^(2)> 0.97). Corresponding to the adsorption configuration of Ni/WC and substrate determined by in-situ FTIR characterization, this study provides a novel insight into the selective conversion of HMF process for functional biofuel and bio-chemicals.
基金financial support from the National Natural Science Foundation of China(52372173,52072034)。
文摘Direct electrolysis of seawater offers a transformative technology for sustainable hydrogen production,circumventing the constraint of freshwater scarcity.However,the serious electrode corrosion and competitive chloride oxidation reactions make oxygen evolution reaction(OER)in seawater extremely challenging.Herein,the low-cost and scalable CoFe layered double hydroxides with Cl^(-)intercalation and decorated with Ce(OH)_(3)(named as CoFe-Cl^(-)/Ce(OH)_(3))catalyst is synthesized via rapid electrodeposition under ambient conditions,which is quickly reconstructed into a CeO_(2)decorated and Cl^(-)intercalated CoFeOOH(CoFeOOH-Cl^(-)/CeO_(2))during OER.Theoretical investigation reveals that Cl^(-)intercalation weakens the adsorption ability of Cl^(-)on Co/Fe atoms and hinders unfavorable coupling with chloride,thereby preventing the chlorine corrosion process and enhancing catalytic stability and activity.The CeO_(2)with hard Lewis acidity preferentially binds to OH-with harder Lewis base to ensure the OH-rich microenvironment around catalyst even under high current operating conditions,thus further enhancing stability and improving OER activity.The functionalized CoFe-Cl^(-)/Ce(OH)_(3)delivers 1000 mA cm^(-2)current density at only 329 mV overpotential with excellent stability for 1000 h under alkaline seawater.Electrochemical experiments elucidate the OER catalytic mechanism in which CeO_(2)serves as a co-catalyst for enriching OH-and CoFeOOH-Cl^(-)is the active species.Our work is a substantial step towards achieving massive and sustainable production of hydrogen fuel from immense seawater.
基金supported by the Highstar Corporation HSD20210118Taihu Electric Corporation 0001。
文摘Since the discovery in 2011,MXenes have become the rising star in the field of two-dimensional materials.Benefiting from the metallic-level conductivity,large and adjustable gallery spacing,low ion diffusion barrier,rich surface chemistry,superior mechanical strength,MXenes exhibit great application prospects in energy storage and conversion,sensors,optoelectronics,electromagnetic interference shielding and biomedicine.Nevertheless,two issues seriously deteriorate the further development of MXenes.One is the high experimental risk of common preparation methods such as HF etching,and the other is the difficulty in obtaining MXenes with controllable surface groups.Recently,Lewis acidic etching,as a brand-new preparation strategy for MXenes,has attracted intensive attention due to its high safety and the ability to endow MXenes with uniform terminations.However,a comprehensive review of Lewis acidic etching method has not been reported yet.Herein,we first introduce the Lewis acidic etching from the following four aspects:etching mechanism,terminations regulation,in-situ formed metals and delamination of multi-layered MXenes.Further,the applications of MXenes and MXene-based hybrids obtained by Lewis acidic etching route in energy storage and conversion,sensors and microwave absorption are carefully summarized.Finally,some challenges and opportunities of Lewis acidic etching strategy are also presented.
基金financial support of the National Natural Science Foundation of China (Grant No. 21263016, 21363015, 51662029, 21863006)the Youth Science Foundation of Jiangxi Province (Grant No. 20192BAB216001)the Key Laboratory of Jiangxi Province for Environment and Energy Catalysis (20181BCD40004)。
文摘Carbon materials have shown remarkable usefulness in facilitating the performance of insulating sulfur cathode for lithium–sulfur batteries owing to their excellent conductivity and porous structure. However,the anxiety is the poor affinity toward polar polysulfides due to the intrinsic nonpolar surface of carbon.Herein, we report a direct pyrolysis of the mixture urea and boric acid to synthesize B/N–codoped hierarchically porous carbon nanosheets(B–N–CSs) as efficient sulfur host for lithium–sulfur battery. The graphene–like B–N–CSs provides high specific surface area and porous structure with abundant micropores(1.1 nm) and low–range mesopores(2.3 nm), thereby constraining the sulfur active materials within the pores. More importantly, the codoped B/N elements can further enhance the polysulfide confinement through strong Li–N and B–S interaction based on the Lewis acid–base theory. These structural superiorities significantly suppress the shuttle effect by both physical confinement and chemical interaction, and promote the redox kinetics of polysulfide conversion. When evaluated as the cathode host, the S/B–N–CSs composite displays the excellent performance with a high reversible capacity up to 772 m A h g–1 at 0.5 C and a low fading rate of ^0.09% per cycle averaged upon 500 cycles. In particular, remarkable stability with a high capacity retention of 87.1% can be realized when augmenting the sulfur loading in the cathode up to 4.6 mg cm^(-2).
基金supported by the National Key R&D Program of China (No. 2016YFE0112800)the European Union’s Horizon 2020 research and innovation programme (No. 690142)+1 种基金the project Agro Cycle (Sustainable techno-economic solutions for the agricultural value chain)the National Natural Science Foundation of China (No. 31671572)
文摘An experimental investigation was conducted to understand the roles of the Br？nsted acid H2SO4 and Lewis acid Al2（SO4）3 in methyl levulinate（ML） production from biomass carbohydrates, including glucose,fructose and cellulose. The product distributions with different catalysts revealed that the Lewis acid was responsible for the isomerization of methyl glucoside（MG）, producing a significant amount of the subsequent product 5-methoxymethylfurfural（MMF）, while the Br？nsted acid facilitated the production of ML from MMF. Al2（SO4）3 was efficient for monosaccharide conversion but not for cellulose. Using ball-milled cellulose with Al2（SO4）3 resulted in a desired ML yield within a reasonable reaction time. The significant catalysis performances of two types of acids will guide the design of efficient catalytic processes for the selective conversion of biomass into levulinate esters.
基金the grant from the National Natural Science Foundation of China （Key Program 20533010）.
文摘Novel Lewis acidic ionic liquids containing thionyl cations and chloroaluminate anions were obtained by one-pot synthesis for the first time. Their acidities were determined by acetonitrile probe on IR spectrography. The ionic liquids were used as catalyst for Friedel-Crafts alkylation of benzene and 1-dodecene. The turnovers of l-dodecene were higher than 99%. Monoalkylbenzene selectivity was 98%, while the 2-substituent product selectivity was 45%.
文摘The self-aldol condensation of aldehydes was investigated with rare-earth cations stabilized by[Si]Beta zeolites in parallel with bulk rare-earth metal oxides.Good catalytic performance was achieved with all Lewis acidic rare-earth cations stabilized by zeolites and yttrium appeared to be the best metal choice.According to the results of several complementary techniques,i.e.,temperature-programmed surface reactions,in situ diffuse reflectance infrared Fourier transform spectroscopy,ultraviolet-visible diffuse reflectance spectroscopy,the reaction pathway and mechanism of the aldehyde self-aldol condensation over Y/Beta catalyst were studied in more detail.Density functional theory calculations revealed that aldol dehydration was the rate-limiting step.The hydroxyl group at the open yttrium site played an important role in stabilizing the transition state of the aldol dimer reducing the energy barrier for its hydration.Lewis acidic Y(OSi)(OH)2 stabilized by zeolites in open configurations were identified as the preferred active sites for the self-aldol condensation of aldehydes.
基金supported by National Natural Science Foundation of China(Nos.51988102,22271275,22201280,22101277)Special Project of High-tech Industrialization of Cooperation between Jilin Province and Chinese Academy of Sciences(No.2022SYHz0004)Changchun Science and Technology Development Plan Funding Project(No.21ZY10).
文摘Ring-opening copolymerization of CO_(2) and epoxides is a promising way to manufacture high value-added materials.Despite a variety of catalyst systems have been reported,the reaction is still limited by low activity and polymer selectivity.Herein,a strategy of polymerization-enhanced Lewis acidity is reported to construct a series of highly efficient polymeric aluminum porphyrin catalysts(PAPCs).The characterization of the coordination equilibrium constant(K_(eq))showed significantly enhanced Lewis acidity of PAPC(K_(eg)=18.2 L/mol)compared to the monomeric counterpart(K_(eq)=6.4 L/mol),accompanied with increased turnover frequency(TOF)from 136 h^(-1) to 5500 h^(-1).Through detailed regulation of Lewis acidity,the highly Lewis acidic PAPC-OTs displayed a record high TOF of 30,200 h^(-1) with polymer selectivity of up to 99%.
基金supported by the National Natural Science Foundation of China (21973013 and 21673040 to S.L, and 21962007 to S.Z)the Natural Science Foundation of Fujian Province of China (2020J02025 to S.L)+2 种基金the Natural Science Foundation of Jiangxi Province (2020BABL203009 to S.Z)the Foundation of Jiangxi Educational Committee (GJJ190697 to S.Z)the Qishan Scholarship Program of Fuzhou University (XRC-17055 to S.L)。
文摘CeO_(2)-based catalysts are emerging as novel candidates for catalyzing nitrogen reduction reaction(NRR).However, despite the increasing amount of experimental and theoretical research, the design of more efficient ceria catalysts for NRR remains a challenge due to the poor knowledge of the catalytic mechanism, particularly the nature of the active sites and how they catalyze NRR. Here, using first-principle calculations, we investigated the NRR catalysis process involving adjacent Ce Lewis acid clusters formed on(111),(110), and(100) facets of CeO_(2) as active sites. Our results revealed that the assembled structures of the Ce Lewis acid as active centers after the oxygen vacancies(Ovs) were opened. The exposed Ce sites on CeO_(2)(111), CeO_(2)(110), and CeO_(2)(100) can cause N_(2) to be adsorbed in a ‘‘lying-down" manner, which facilitates the N2 activation and thus leads to much higher NRR activity. Furthermore, from the perspective of electronic structure, we establish two useful descriptors for assessing the NRR activity on ceria with Ovs:The N–N bond strength of the adsorbed N_(2) and the adsorption energy of the *N_(2)H intermediate. This work thus provides direct guidance for the design of more-effective oxide catalysts without the use of scarce metals.
文摘The azides were reduced to the corresponding amines by two new metal/Lewis acid systems in water or in aqueous EtOH in yields ranging from 80%-95%. The reaction rates were faster in water than in aqueous EtOH in most cases. All 16 azides with different functional groups were well reduced to the corresponding amines in excellent yields and reaction rates.
基金the National Science Foundation for Excellent Young Scholars of China(21922815)the Key Research and Development(R&D)Projects of Shanxi Province(201903D121007)+3 种基金the Natural Science Foundations of Shanxi Province(201801D221156)the DNL Cooperation Fund of CAS(DNL180308)the Science and Technology Service Network Initiative of CAS(KFJ-STS-ZDTP-068)the Youth Innovation Promotion Association of CAS。
文摘The incorporation of boron into carbon material can significantly enhance its capacity performances.However,the origin of the promotion effect of boron doping on electrochemical performances is still unclear,in part due to the inadequate exposure of boron configurations resulting from the complexity of traditional carbon materials.To overcome this issue,herein,a series of boron-doped graphene with highly-exposed boron configurations are prepared by tuning annealing temperature.Then the correlation between boron configurations and the electrochemical performances is investigated.The combination of density-functional theory(DFT)computation and NH3-TPD/Py-FTIR indicates that the BCO_(2)configuration formed on the surface of graphene is easier to accept lone-pair electrons than BC_(2)O and BC_(3)configurations due to the stronger Lewis acidity.Such an electronic structure can effectively reduce the number of unstable electron donors and stabilize the electrochemical interface,which is proved by NMR,and critical for improving the electrochemical performances.Further experiments confirm that the optimized BG800 with the largest amount of BCO_(2)configuration presents ultralow leak current,improved cyclic stability,and better rate performance in SBPBF4/PC.This work would provide an insight into the design of high-performance boron-doped carbon materials towards energy storage.
基金A Project Funded by Jiangsu Natural Science Foundation of China(No.BK2011369)
文摘Lewis acidic ionic liquids were used to catalyze the reaction of epoxypropane with POCl3. Considering the lower cost and catalytic activities, we concluded that [Et3NH]Cl/AlCl3 was the most attractive ionic liquid from an economical point of view. But it would be easily inactivated because of sensitive to water and air. Moreover, it could not be reused easily because of difficulty recovery in the reaction. However, supporting [Et3NH]Cl/AlCl3 catalyst could resolve above problems. Supporting [Et3NH]Cl/ AlCl3 catalyst could be separated by filter easily and reused 5 times in 98% yield. Furthermore, the catalyst was applicable to other epoxy ether cleaving reactions.
基金Financial supports from MOST of China(973 program,No. 2011CB808600)National Natural Science Foundation of China(Nos.21072091 and 21372195)the Low Carbon Fatty Amine Engineering Research Center of Zhejiang Province(No. 2012E10033)
文摘A substitution reaction of amines with alcohols for N-alkylated amines has been developed using inexpensive AlCl3without any ligand or additive.Either aromatic or aliphatic amines and primary or secondary alcohols perform the AlCl3-mediated reaction smoothly to afford various N-alkylated amines in satisfactory yields.
文摘Treatment of steroidal sapogenin diosgenin 1 with Lewis acid ethereal trifluoroborane in acetic anhydride at room temperature afforded a new type of pseudosapugenin 23, 26-diacetyl-△22(23)- pseudo-sapogenin 3 and its C-20 isomer 4 in 54% and 19% yield respectively.The possible mechanism was also suggested.
基金partially supported by a Grant-in-Aid for Science Research from the Japan Society for the Promotion of Science(JSPS)the Global COE Program,the University of Tokyo,the Japan Science and Technology Agency(JST)the Ministry of Education,Culture,Sports,Science and Tech-nology(MEXT,Japan)
文摘Metal nanoparticle catalysts, especially gold and its bimetallic nanoparticle catalysts, have been widely used in organic transformations as powerful and green catalysts. The concept of employing two distinct catalysts in one reaction system, such as in cooperative and synergistic catalysis, is a powerful strategy in homogeneous catalysis. However, the adaption of such a strategy to metal nanoparticle catalysis is still under development. Recently, we have found that cooperative catalytic systems of gold/palladium bimetallic nanoparticles and Lewis acid can be used for the N‐alkylation of primary amides through hydrogen autotransfer reaction between amide and alcohol. Herein, the results of a detailed investigation into the effects of Lewis acids on this hydrogen autotransfer reac‐tion are reported. It was found that the choice of Lewis acid affected not only the reaction pathway leading to the desired product, but also other reaction pathways that produced several intermedi‐ates and by‐products. Weak Lewis acids, such as alkaline‐earth metal triflates, were found to be optimal for the desired N‐alkylation of amides.
基金Supported by the National Natural Science Foundation of China(21376011)the Fundamental Research Foundation of Sinopec(X505015)
文摘For efficient removal of thiophenic sulfur （S-） compounds from oils, a novel method is proposed here, i.e. one-pot alkylation desulfurization （OADS）, in which oil insoluble chlorinated polymer such as polyvinyl chlo- ride （PVC） is used as the alkylating regent with Lewis acid as catalyst. The aromatic S-compounds are grafted to the polymer through Friedel-Crafts reaction and removed facilely along with the polymer. The OADS mechanism is identified by scanning electron microscope and analyzer with surface area and pore size of the polymer. The influ- ence of some factors on the OADS is studied, e.g. the type and amount of chlorinated polymers and Lewis acids. It is nroved that thionhene and benzothioDhene can be removed efficiently from oil by PVC＋AlCl3 mixture even in the presence of 25% （by mass） of benzene due to the synergetic effects of the adsorptive desulfurization of AlCl3 and the alkylation desulfurization of PVC.
基金financial support from the National Natural Science Foundation of China(Nos.22001248 and 22173103)the Fundamental Research Funds for the Central Universities and the University of the Chinese Academy of Sciences。
文摘We report the Lewis acid catalysis of aryldiazonium salts,and their Lewis acidity applications in photogeneration of aryl radicals under additive-,photocatalyst-and transition metal-free conditions.In this visible light-mediated transformation,the Lewis acidic character of aryldiazonium salts enables access to the photoactive charge transfer complex with dichalcogenides.The usefulness and versatility of this new protocol are demonstrated through the chalcogenation of a variety of aryldiazonium salts.
基金The work was financially supported by the National Natural Science Foundation of China(No.20634040).
文摘Chloro(5,10,15,20-tetraphenyl-porphyrinato)-aluminum/tetraethylammonium bromide(Et4NBr)in combination with bulky Lewis acid was used for the copolymerization of CO_2 and cyclohexene oxide(CHO).Bulky Lewis acid having substituents at the ortho positions of the phenolate ligands,like methylaluminum bis(2,6-di-tert-butyl-4-methylphenolate), significantly shortened the induction period and raised the catalytic activity,the corresponding turnover frequency reached 44.9 h^(-1)in 9 h,which was 23.8% higher than th...
基金Project supported by China Petroleum&Chemical Corporation (J418013-3)。
文摘Herein,a new mechanism involving Lewis acid-oxygen vacancy interfacial synergistic catalysis fo r aniline N,N-diethylation with ethanol was proposed,and the SO4^2-/Ce0.84Zr0.16O2-WO3-ZrO2 catalyst(SCWZ)with both Lewis acid sites and oxygen vacancies was synthesized by the hydrothermal method,which shows better catalytic activity than the reported solid acidic catalysts.Besides,the SO4^2-/ZrO2(SZ)and SO4^2-/WO3-ZrO2(SWZ)catalysts were also prepared and compared with SCWZ to investigate the synergistic effect of each component.The SO4^2-and WO3 mainly generate Lewis acid by bonding with ZrO2,which is beneficial for the fracture of the N-H bond in aniline.The Ce0.84Zr0.16O2 solid solution mainly plays a vital role in generating the oxygen vacancies as the interface active species,which can participate in stripping-OH from ethanol,then the carbocation will also be released,which only needs1.3805 kcal/mol energy,calculated by density functional theory(DFT),to be input.In comparison,the traditional reaction mechanism needs the Br■nsted acidic sites to promote the protonation of ethanol,then dehydration and subsequent formation of carbocation followed,and 108.6846 kcal/mol energy needs to be input,which is far higher than that of the new mechanism.The apparent activation energy(Ea)over SCWZ was measured by experiment to be 34.09 kJ/mol,which is much lower than that of SWZ(47.10 kJ/mol)and SZ(54.37 kJ/mol),illustrating comparatively preferable kinetics for SCWZ than that of SWZ and SZ.Besides,the conversion of aniline and selectivity to N,N-diethylaniline over SCWZ reach almost 100%and 73%,respectively,The SCWZ can be renewed for 4 times without rapid deactivation,and the longevity of SCWZ is longer than that of SWZ and SZ,as the loaded SO4^2-and tetragonal ZrO2 are stabilized by Ce0.84Zr0.16O2 and WO3,respectively.
文摘Lewis acidic guanidinium ionic liquid（LAGIL） 2c was used as a novel, efficient and recyclable catalyst for aminolysis of epoxides under solvent-free and room temperature conditions, giving the corresponding β-amino alcohols with moderate to excellent regioselectivity（up to 91：9） in high yields（up to 97%）. In addition, LAGIL 2c was recycled three times without any loss of catalytic activity and selectivity to the product.
