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
High-capacity LiBH_(4)is a promising solid hydrogen storage material.However,the large electron cloud density between the B-H bonds in LiBH_(4)induces high dehydrogenation temperatures and sluggish dehydrogenation kin...High-capacity LiBH_(4)is a promising solid hydrogen storage material.However,the large electron cloud density between the B-H bonds in LiBH_(4)induces high dehydrogenation temperatures and sluggish dehydrogenation kinetics.To solve the above problems,it is proposed to enhance the hydrogen storage properties of LiBH_(4)through the synergistic effect of Brønsted and Lewis acid in Hβzeolite.Composite hydrogen storage systems with different mass ratios were prepared by simple ball-milling.At a LiBH_(4)-to-Hβmass ratio of 6:4,the 6LiBH_(4)-4Hβsystem released hydrogen at 190℃and achieved a hydrogen release capacity of 7.0 wt%H_(2)upon heating to 400℃.More importantly,the hydrogen release capacity of the system reached 6.02 wt%at 350℃under isothermal conditions after 100 min and 7.2 wt%at 400℃under isothermal conditions after 80 min,whereas the pristine LiBH_(4)only achieved 2.2 wt%.The improvement in hydrogen storage performance of the system was mainly attributed to two factors:(i)Lewis acid sites with acceptable electrons in the Hβweaken the electron density of B-H bonds in LiBH_(4),and(ii)the H+proton from the Brønsted acid sites and H−of LiBH_(4)undergo a H^(+)+H^(−)=H_(2)reaction.Theoretical calculations revealed that the Lewis and Brønsted acid sites in the Hβzeolite are conducive to the weakening of B-H bonds and that storage charge transfer occurs near the Lewis acid sites.The present work provides new insights into improving the hydrogen storage performance of LiBH_(4)by weakening the B-H bonds in the LiBH_(4).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
目的:了解P-选择素及其配体sLeA、sLeX在食管癌组织及区域淋巴结中的表达,探讨其与食管癌侵袭转移的关系。方法:应用组织芯片技术结合免疫组化检测食管鳞癌86例及其淋巴结P-选择素和sialy lewis A(sLeA)、sialylewis X(sLe X)的表达情况...目的:了解P-选择素及其配体sLeA、sLeX在食管癌组织及区域淋巴结中的表达,探讨其与食管癌侵袭转移的关系。方法:应用组织芯片技术结合免疫组化检测食管鳞癌86例及其淋巴结P-选择素和sialy lewis A(sLeA)、sialylewis X(sLe X)的表达情况,并与16例正常食管鳞状上皮对照。结果:P-选择素在食管癌组织、正常食管鳞状上皮表达率分别为59.3%、12.5%(P<0.05),在转移淋巴结、非转移淋巴结中表达率分别为92.9%、31.3%(P<0.05)。sLeA在食管癌组织,正常食管组织中表达率分别为77.9%、6.25%(P<0.05),在转移淋巴结和非转移淋巴结中表达率分别为97.6%、20.3%(P<0.05)。sLe X食管癌组织、正常食管组织中表达率分别为15.1%、6.25%(P>0.05)。P-选择素和配体sLeA过度表达与食管鳞癌病理分级,TNM分期及淋巴结转移成显著相关性;而配体sLeX在食管癌组织中无过度表达。结论:P-选择素和配体sLeA在食管鳞癌组织、转移淋巴结中表达率明显升高,其与食管癌的侵袭转移有一定关系;配体sLeX与食管癌侵袭转移无关。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
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supported by the National Natural Science Foundation of China(No.52201274)the Project of Education Department of Shanxi Province(No.22JK0419).
文摘High-capacity LiBH_(4)is a promising solid hydrogen storage material.However,the large electron cloud density between the B-H bonds in LiBH_(4)induces high dehydrogenation temperatures and sluggish dehydrogenation kinetics.To solve the above problems,it is proposed to enhance the hydrogen storage properties of LiBH_(4)through the synergistic effect of Brønsted and Lewis acid in Hβzeolite.Composite hydrogen storage systems with different mass ratios were prepared by simple ball-milling.At a LiBH_(4)-to-Hβmass ratio of 6:4,the 6LiBH_(4)-4Hβsystem released hydrogen at 190℃and achieved a hydrogen release capacity of 7.0 wt%H_(2)upon heating to 400℃.More importantly,the hydrogen release capacity of the system reached 6.02 wt%at 350℃under isothermal conditions after 100 min and 7.2 wt%at 400℃under isothermal conditions after 80 min,whereas the pristine LiBH_(4)only achieved 2.2 wt%.The improvement in hydrogen storage performance of the system was mainly attributed to two factors:(i)Lewis acid sites with acceptable electrons in the Hβweaken the electron density of B-H bonds in LiBH_(4),and(ii)the H+proton from the Brønsted acid sites and H−of LiBH_(4)undergo a H^(+)+H^(−)=H_(2)reaction.Theoretical calculations revealed that the Lewis and Brønsted acid sites in the Hβzeolite are conducive to the weakening of B-H bonds and that storage charge transfer occurs near the Lewis acid sites.The present work provides new insights into improving the hydrogen storage performance of LiBH_(4)by weakening the B-H bonds in the LiBH_(4).
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.
