A composite metal-organic frameworks(MOFs)structure,designated as Co-hmta@La-salen,was synthesized through coordination interactions between a one-dimensional lanthanum MOFs(La-salen)with high density of uncoordinated...A composite metal-organic frameworks(MOFs)structure,designated as Co-hmta@La-salen,was synthesized through coordination interactions between a one-dimensional lanthanum MOFs(La-salen)with high density of uncoordinated imine(-CH=N-)groups and a cobalt-based MOFs(Co-hmta)structure prepared using hydrogen bonding stacking with hexamethylenetetramine(hmta)as the organic ligand.Subsequently,the Co-hmta@La-salen composite was chosen as a template for the pyrolysis process to synthesize a La(OH)_(3)supported metallic Co catalyst incorporating carbon-nitrogen(Co/La(OH)_(3)-CNhmta)catalyst.The catalytic results show that Co/La(OH)_(3)-CN-hmta(54%and 46%selectivity for aniline and N-phenylbenzylamine,respectively)displays superior cascade performance compared to classic Co/La(OH)_(3)-CN-nit catalyst(69%and 31%selectivity for aniline and N-phenylbenzylamine,respectively).Moreover,the kinetic test results indicate that N-alkylation is the rate-limiting step of the overall cascade reaction.The Co/La(OH)_(3)-CN-hmta catalyst can be separated from the reaction system using a magnet,and it also exhibits good cyclic stability.All of these suggest that the“MOFs plus MOFs via coordination”templating method can be employed as an efficient strategy for the preparation of supported catalysts.展开更多
The thermal decomposition characteristic of ammonium perchlorate(AP)represents a critical factor in determining the performance of solid propellants,which has aroused significant interest on the structure and performa...The thermal decomposition characteristic of ammonium perchlorate(AP)represents a critical factor in determining the performance of solid propellants,which has aroused significant interest on the structure and performance improvement of kinds of catalysts.In this study,bimetallic metal-organic frameworks(MOFs),such as CuCo-BTC(BTC=1,3,5-Benzenetricarboxylic acid,H_(3)BTC),CuNi-BTC,and CoNi-BTC,were synthesized by solvothermal(ST)and spray-drying(SD)methods,and then calcined at 400℃for 2 h to form metal oxides.The catalysts as well as their catalytic effects for AP decomposition were characterized by FTIR,XRD,SEM,XPS,TG,DSC,TG-IR,EIS,CV,and LSV.It was found that the rapid coordination of metal ions with ligands during spray drying may lead to catalytic structural defects,promoting the exposure of reactive active sites and increasing the catalytic active region.The results showed that the addition of 2 wt%binary transition metal oxides(BTMOs)as catalysts significantly reduced the high-temperature decomposition(HTD)temperature of AP and enhanced its heat release.Of particular significance is the observation that SD-CoNiO_(x),prepared by spray-drying,reduced the decomposition temperature of AP from 413.26℃(pure AP)to 306℃and enhanced the heat release from 256.79 J/g(pure AP)to 1496.82 J/g,while concomitantly reducing the activation energy by 42%.By analysing the gaseous products during the decomposition of AP+SD-CoNiO_(x)and AP+ST-CoNiO_(x),it was found that SD-CoNiO_(x)could significantly increase the content of high-valent nitrogen oxides during the AP decomposition reaction,which indicates that the BTMOs prepared by spray-drying in the reaction system are more conducive to accelerating the electron transfer in the thermal decomposition process of AP,and can provide a high concentration of reactive oxygen species that oxidize AP to high-valent nitrogen oxide-containing compounds.The present study shows that the structure selectivity of the spray-drying technique influences surfactant molecular arrangement on catalyst surfaces,resulting in their ability to promote higher electron transfer during the catalytic process.Therefore,BTMOs prepared by spray drying method have higher potential for application.展开更多
Porous structures o er highly accessible surfaces and rich pores, which facilitate the exposure of numerous active sites for photocatalytic reactions, leading to excellent performances. Recently, metal–organic framew...Porous structures o er highly accessible surfaces and rich pores, which facilitate the exposure of numerous active sites for photocatalytic reactions, leading to excellent performances. Recently, metal–organic frameworks(MOFs) have been considered ideal precursors for well-designed semiconductors with porous structures and/or heterostructures, which have shown enhanced photocatalytic activities. In this review, we summarize the recent development of porous structures, such as metal oxides and metal sulfides, and their heterostructures, derived from MOF-based materials as catalysts for various light-driven energy-/environment-related reactions, including water splitting, CO_2 reduction, organic redox reaction, and pollution degradation. A summary and outlook section is also included.展开更多
At present, the problem of electromagnetic wave(EMW) pollution is critical, and the design of highperformance absorbers is of great significance. Based on the synergy between dielectric and magnetic losses, and betwee...At present, the problem of electromagnetic wave(EMW) pollution is critical, and the design of highperformance absorbers is of great significance. Based on the synergy between dielectric and magnetic losses, and between multicomponents in heterostructures, the development of light-weight absorbers with a strong absorption capability and multiple scattering is a promising strategy to achieve highperformance absorbers. In this work, CoFe-MOF precursors with a bouquet-like structure were prepared via the hydrothermal method, and Co_(7)Fe_(3)/C and Co_(9)S_(8)/FeCoS_(2)/C composites were obtained through a carbonization and sulfuration treatment during the high-temperature pyrolysis process, respectively. The experimental and theoretical results show that the Co_(9)S_(8)/FeCoS_(2)/C composite has a better EMW absorption performance, and its optimal reflection loss(RL) value is-53.9 d B at a low filler loading of 20 wt.%,which is due to the S doping that enhances the interface polarization relaxation process and improves the impedance matching characteristics. Moreover, the Co_(9)S_(8)/FeCoS_(2)/C composite can be as candidates of high-efficiency absorbers in extreme application environments.展开更多
Nitrogen-doped carbon materials as promising oxygen reduction reaction(ORR) electrocatalysts attract great interest in fuel cells and metal-air batteries because of their relatively high activity, high surface area, h...Nitrogen-doped carbon materials as promising oxygen reduction reaction(ORR) electrocatalysts attract great interest in fuel cells and metal-air batteries because of their relatively high activity, high surface area, high conductivity and low cost. To maximize their catalytic efficiency, rational design of efficient electrocatalysts with rich exposed active sites is highly desired. Besides, due to the complexity of nitrogen species, the identification of active nitrogen sites for ORR remains challenging. Herein, we develop a facile and scalable template method to construct high-concentration nitrogen-doped carbon hollow frameworks(NC), and reveal the effect of different nitrogen species on theirORRactivity on basis of experimental analysis and theoretical calculations. The formation mechanism is clearly revealed, including low-pressure vapor superassembly of thin zeolitic imidazolate framework(ZIF-8) shell on ZnO templates,in situ carbonization and template removal. The obtained NC-800 displays better ORR activity compared with other NC-700 and NC-900 samples. Our results indicate that the superior ORR activity of NC-800 is mainly attributed to its content balance of three nitrogen species. The graphitic N and pyrrolic N sites are responsible for lowering the working function, while the pyridinic N and pyrrolic N sites as possible active sites are beneficial for increasing the density of states.展开更多
Broadband electromagnetic(EM)wave absorption materials play an important role in military stealth and health protection.Herein,metal–organic frameworks(MOFs)-derived magnetic-carbon CoNiM@C(M=Cu,Zn,Fe,Mn)microspheres...Broadband electromagnetic(EM)wave absorption materials play an important role in military stealth and health protection.Herein,metal–organic frameworks(MOFs)-derived magnetic-carbon CoNiM@C(M=Cu,Zn,Fe,Mn)microspheres are fabricated,which exhibit flower-like nano–microstructure with tunable EM response capacity.Based on the MOFs-derived CoNi@C microsphere,the adjacent third element is introduced into magnetic CoNi alloy to enhance EM wave absorption performance.In term of broadband absorption,the order of efficient absorption bandwidth(EAB)value is Mn>Fe=Zn>Cu in the CoNiM@C microspheres.Therefore,MOFs-derived flower-like CoNiMn@C microspheres hold outstanding broadband absorption and the EAB can reach up to 5.8 GHz(covering 12.2–18 GHz at 2.0 mm thickness).Besides,off-axis electron holography and computational simulations are applied to elucidate the inherent dielectric dissipation and magnetic loss.Rich heterointerfaces in CoNiMn@C promote the aggregation of the negative/positive charges at the contacting region,forming interfacial polarization.The graphitized carbon layer catalyzed by the magnetic CoNiMn core offered the electron mobility path,boosting the conductive loss.Equally importantly,magnetic coupling is observed in the CoNiMn@C to strengthen the magnetic responding behaviors.This study provides a new guide to build broadband EM absorption by regulating the ternary magnetic alloy.展开更多
Lithium-selenium batteries,as an advanced rechargeable battery system,have attracted wide attention.However,its application is hurdled by the ambiguous underlying mechanism such as the unclear active phase and the key...Lithium-selenium batteries,as an advanced rechargeable battery system,have attracted wide attention.However,its application is hurdled by the ambiguous underlying mechanism such as the unclear active phase and the key role of the host materials.Herein,a three-dimensional(3D) functional matrix derived from the Co/Znmetal organic framework is synthesized to unravel the questions raised.It reveals that the strong interaction and voids in the 3D matrix serve to anchor the amorphous Se with high electrochemical properties.The obtained 3DC/Se exhibits 544.2 and 273.2 mAh·g^(-1) t current densities of 0.1C and 2.0C,respectively,with a diffusion-controlled mechanism.The excessive amount of Se beyond the loading capacity of the matrix leads to the formation of trigonal phase Se,which shows an unsatisfying electrochemical property.展开更多
The construction of CoeMn mixed-metal oxide catalysts derived from bimetallic metaleorganic frameworks(MOFs)has great significance for catalytic destruction of toluene.Hence,a series of Co_(a)Mn_(b)O_(x)-MOFs with dif...The construction of CoeMn mixed-metal oxide catalysts derived from bimetallic metaleorganic frameworks(MOFs)has great significance for catalytic destruction of toluene.Hence,a series of Co_(a)Mn_(b)O_(x)-MOFs with different physicochemical properties were successfully synthesized via pyrolysis of CoeMn bimetallic MOFs.Attributing to the higher specific surface area,more active sites(Co^(3+)and Mn^(3+)),stronger reducibility,and abundant defect sites,the as-prepared Co_(1)Mn_(1)O_(x)-MOFs displayed an optimal catalytic performance,especially the excellent water vapor resistance.The result of the in situ diffuse reflectance infrared Fourier transform spectroscopy demonstrated that toluene can be degraded at relatively low temperatures(<100℃).Benzyl alcohol,benzaldehyde,benzoic acid,and maleic anhydride were the main intermediate products in toluene degradation process.This work reveals the value of bimetallic MOFs derived Co-Mn oxides for toluene oxidation and presents a novel avenue for designing mixed-metal oxide catalysts with potential applications in volatile organic compounds(VOCs)catalytic oxidation.展开更多
Silicon is recognized as the most advantageous next-generation anode material for LIBs in terms of its extremely high theoretical capacity and appropriate operating voltage.However,the application of Si anode is limit...Silicon is recognized as the most advantageous next-generation anode material for LIBs in terms of its extremely high theoretical capacity and appropriate operating voltage.However,the application of Si anode is limited by huge volume expansion emerging with cycling,which in turn induces the collapse of the electrode structure,resulting in rapid capacity decay.Here,we report a strategy using self-swelling artificial laponite to prepare a laponite/MXene/CNT composite framework with both rigidity and flexibility,which can excellently address these challenges of Si anode.The self-swelling artificial laponite participates in the construction of hierarchical and porous structures,providing sufficient buffer space to mitigate the volume expansion of the LixSi alloying reaction.Meanwhile,tough and tightly cross-linked silicate nanosheets can improve the mechanical strength of the framework for strong structural stability.More importantly,the negative charge between the layers of artificial laponite can effectively promote fast Li-ion transport in the electrode.This free-standing silicon anode enables the preparation of high areal capacity electrodes to further enhance the energy density of LIBs and a higher reversible capacity of 2381.8 mAh/g at 0.1 C after 50 cycles with an initial coulombic of 85.6%.This work provides a simple and practical fabrication strategy for developing high-performance Si-based batteries,which can speed up their commercialization.展开更多
基金Project supported by the Natural Science Foundation of Jiangsu Province (BK20210066)Natural Science Foundation of Heilongjiang Province (ZD2022E007).
文摘A composite metal-organic frameworks(MOFs)structure,designated as Co-hmta@La-salen,was synthesized through coordination interactions between a one-dimensional lanthanum MOFs(La-salen)with high density of uncoordinated imine(-CH=N-)groups and a cobalt-based MOFs(Co-hmta)structure prepared using hydrogen bonding stacking with hexamethylenetetramine(hmta)as the organic ligand.Subsequently,the Co-hmta@La-salen composite was chosen as a template for the pyrolysis process to synthesize a La(OH)_(3)supported metallic Co catalyst incorporating carbon-nitrogen(Co/La(OH)_(3)-CNhmta)catalyst.The catalytic results show that Co/La(OH)_(3)-CN-hmta(54%and 46%selectivity for aniline and N-phenylbenzylamine,respectively)displays superior cascade performance compared to classic Co/La(OH)_(3)-CN-nit catalyst(69%and 31%selectivity for aniline and N-phenylbenzylamine,respectively).Moreover,the kinetic test results indicate that N-alkylation is the rate-limiting step of the overall cascade reaction.The Co/La(OH)_(3)-CN-hmta catalyst can be separated from the reaction system using a magnet,and it also exhibits good cyclic stability.All of these suggest that the“MOFs plus MOFs via coordination”templating method can be employed as an efficient strategy for the preparation of supported catalysts.
基金supported by the National Natural ScienceFoundation of China(Grant No.52203332)。
文摘The thermal decomposition characteristic of ammonium perchlorate(AP)represents a critical factor in determining the performance of solid propellants,which has aroused significant interest on the structure and performance improvement of kinds of catalysts.In this study,bimetallic metal-organic frameworks(MOFs),such as CuCo-BTC(BTC=1,3,5-Benzenetricarboxylic acid,H_(3)BTC),CuNi-BTC,and CoNi-BTC,were synthesized by solvothermal(ST)and spray-drying(SD)methods,and then calcined at 400℃for 2 h to form metal oxides.The catalysts as well as their catalytic effects for AP decomposition were characterized by FTIR,XRD,SEM,XPS,TG,DSC,TG-IR,EIS,CV,and LSV.It was found that the rapid coordination of metal ions with ligands during spray drying may lead to catalytic structural defects,promoting the exposure of reactive active sites and increasing the catalytic active region.The results showed that the addition of 2 wt%binary transition metal oxides(BTMOs)as catalysts significantly reduced the high-temperature decomposition(HTD)temperature of AP and enhanced its heat release.Of particular significance is the observation that SD-CoNiO_(x),prepared by spray-drying,reduced the decomposition temperature of AP from 413.26℃(pure AP)to 306℃and enhanced the heat release from 256.79 J/g(pure AP)to 1496.82 J/g,while concomitantly reducing the activation energy by 42%.By analysing the gaseous products during the decomposition of AP+SD-CoNiO_(x)and AP+ST-CoNiO_(x),it was found that SD-CoNiO_(x)could significantly increase the content of high-valent nitrogen oxides during the AP decomposition reaction,which indicates that the BTMOs prepared by spray-drying in the reaction system are more conducive to accelerating the electron transfer in the thermal decomposition process of AP,and can provide a high concentration of reactive oxygen species that oxidize AP to high-valent nitrogen oxide-containing compounds.The present study shows that the structure selectivity of the spray-drying technique influences surfactant molecular arrangement on catalyst surfaces,resulting in their ability to promote higher electron transfer during the catalytic process.Therefore,BTMOs prepared by spray drying method have higher potential for application.
基金supported by the National Natural Science Foundation of China (Grant Nos. 21671085, 21701063)the Jiangsu Province Science Foundation for Youths (BK20150237)+1 种基金the Natural Science Foundation of Jiangsu Province (BK20161160)the Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘Porous structures o er highly accessible surfaces and rich pores, which facilitate the exposure of numerous active sites for photocatalytic reactions, leading to excellent performances. Recently, metal–organic frameworks(MOFs) have been considered ideal precursors for well-designed semiconductors with porous structures and/or heterostructures, which have shown enhanced photocatalytic activities. In this review, we summarize the recent development of porous structures, such as metal oxides and metal sulfides, and their heterostructures, derived from MOF-based materials as catalysts for various light-driven energy-/environment-related reactions, including water splitting, CO_2 reduction, organic redox reaction, and pollution degradation. A summary and outlook section is also included.
基金financially supported from the National Natural Science Foundation of China (Nos. 61701386 and 21975196)the Young Star Project of Science and Technology of Shaanxi Province(No. 2019KJXX-033)the Youth Innovation Team of Shaanxi Universities:Metal corrosion protection and surface engineering technology。
文摘At present, the problem of electromagnetic wave(EMW) pollution is critical, and the design of highperformance absorbers is of great significance. Based on the synergy between dielectric and magnetic losses, and between multicomponents in heterostructures, the development of light-weight absorbers with a strong absorption capability and multiple scattering is a promising strategy to achieve highperformance absorbers. In this work, CoFe-MOF precursors with a bouquet-like structure were prepared via the hydrothermal method, and Co_(7)Fe_(3)/C and Co_(9)S_(8)/FeCoS_(2)/C composites were obtained through a carbonization and sulfuration treatment during the high-temperature pyrolysis process, respectively. The experimental and theoretical results show that the Co_(9)S_(8)/FeCoS_(2)/C composite has a better EMW absorption performance, and its optimal reflection loss(RL) value is-53.9 d B at a low filler loading of 20 wt.%,which is due to the S doping that enhances the interface polarization relaxation process and improves the impedance matching characteristics. Moreover, the Co_(9)S_(8)/FeCoS_(2)/C composite can be as candidates of high-efficiency absorbers in extreme application environments.
基金supported by the National Natural Science Foundation of China (51832004 and 51521001)the National Key Research and Development Program of China (2016YFA0202603)+2 种基金the Natural Science Foundation of Hubei Province (2019CFA001)the Programme of Introducing Talents of Discipline to Universities (B17034)the Yellow Crane Talent (Science & Technology) Program of Wuhan City。
文摘Nitrogen-doped carbon materials as promising oxygen reduction reaction(ORR) electrocatalysts attract great interest in fuel cells and metal-air batteries because of their relatively high activity, high surface area, high conductivity and low cost. To maximize their catalytic efficiency, rational design of efficient electrocatalysts with rich exposed active sites is highly desired. Besides, due to the complexity of nitrogen species, the identification of active nitrogen sites for ORR remains challenging. Herein, we develop a facile and scalable template method to construct high-concentration nitrogen-doped carbon hollow frameworks(NC), and reveal the effect of different nitrogen species on theirORRactivity on basis of experimental analysis and theoretical calculations. The formation mechanism is clearly revealed, including low-pressure vapor superassembly of thin zeolitic imidazolate framework(ZIF-8) shell on ZnO templates,in situ carbonization and template removal. The obtained NC-800 displays better ORR activity compared with other NC-700 and NC-900 samples. Our results indicate that the superior ORR activity of NC-800 is mainly attributed to its content balance of three nitrogen species. The graphitic N and pyrrolic N sites are responsible for lowering the working function, while the pyridinic N and pyrrolic N sites as possible active sites are beneficial for increasing the density of states.
基金supported by the National Natural Science Foundation of China(52231007,12327804,T2321003,22088101)this work was supported in part by the National Key Research Program of China under Grant 2021YFA1200600,and Shanghai Sailing Program(22YF1447800).
文摘Broadband electromagnetic(EM)wave absorption materials play an important role in military stealth and health protection.Herein,metal–organic frameworks(MOFs)-derived magnetic-carbon CoNiM@C(M=Cu,Zn,Fe,Mn)microspheres are fabricated,which exhibit flower-like nano–microstructure with tunable EM response capacity.Based on the MOFs-derived CoNi@C microsphere,the adjacent third element is introduced into magnetic CoNi alloy to enhance EM wave absorption performance.In term of broadband absorption,the order of efficient absorption bandwidth(EAB)value is Mn>Fe=Zn>Cu in the CoNiM@C microspheres.Therefore,MOFs-derived flower-like CoNiMn@C microspheres hold outstanding broadband absorption and the EAB can reach up to 5.8 GHz(covering 12.2–18 GHz at 2.0 mm thickness).Besides,off-axis electron holography and computational simulations are applied to elucidate the inherent dielectric dissipation and magnetic loss.Rich heterointerfaces in CoNiMn@C promote the aggregation of the negative/positive charges at the contacting region,forming interfacial polarization.The graphitized carbon layer catalyzed by the magnetic CoNiMn core offered the electron mobility path,boosting the conductive loss.Equally importantly,magnetic coupling is observed in the CoNiMn@C to strengthen the magnetic responding behaviors.This study provides a new guide to build broadband EM absorption by regulating the ternary magnetic alloy.
基金financially supported by the National Natural Science Foundation of China (Nos.51901189 and 51802265)Shaanxi Provincial Key R&D Program (No.2021KWZ17)+1 种基金China Postdoctoral Science Foundation Grant (No. 2020M683552)the Natural Science Foundation of Chongqing (No.cstc2020jcyj-msxmX0859)。
文摘Lithium-selenium batteries,as an advanced rechargeable battery system,have attracted wide attention.However,its application is hurdled by the ambiguous underlying mechanism such as the unclear active phase and the key role of the host materials.Herein,a three-dimensional(3D) functional matrix derived from the Co/Znmetal organic framework is synthesized to unravel the questions raised.It reveals that the strong interaction and voids in the 3D matrix serve to anchor the amorphous Se with high electrochemical properties.The obtained 3DC/Se exhibits 544.2 and 273.2 mAh·g^(-1) t current densities of 0.1C and 2.0C,respectively,with a diffusion-controlled mechanism.The excessive amount of Se beyond the loading capacity of the matrix leads to the formation of trigonal phase Se,which shows an unsatisfying electrochemical property.
基金financial support of the National Natural Science Foundation of China(22408252,22078215)Natural Science Foundation for Youths of Shanxi Province(202103021223347)+1 种基金Taiyuan Institute of Technology Talent Introduction Research funding Project(2022KJ010)Shanxi Province Science and Technology Major Special Plan“Reveal The List and Take Charge”Project(202201090301014).
文摘The construction of CoeMn mixed-metal oxide catalysts derived from bimetallic metaleorganic frameworks(MOFs)has great significance for catalytic destruction of toluene.Hence,a series of Co_(a)Mn_(b)O_(x)-MOFs with different physicochemical properties were successfully synthesized via pyrolysis of CoeMn bimetallic MOFs.Attributing to the higher specific surface area,more active sites(Co^(3+)and Mn^(3+)),stronger reducibility,and abundant defect sites,the as-prepared Co_(1)Mn_(1)O_(x)-MOFs displayed an optimal catalytic performance,especially the excellent water vapor resistance.The result of the in situ diffuse reflectance infrared Fourier transform spectroscopy demonstrated that toluene can be degraded at relatively low temperatures(<100℃).Benzyl alcohol,benzaldehyde,benzoic acid,and maleic anhydride were the main intermediate products in toluene degradation process.This work reveals the value of bimetallic MOFs derived Co-Mn oxides for toluene oxidation and presents a novel avenue for designing mixed-metal oxide catalysts with potential applications in volatile organic compounds(VOCs)catalytic oxidation.
基金supported by the National Natural Science Foundation of China(No.51871113)Natural Science Foundation of Jiangsu Province(No.BK20200047).
文摘Silicon is recognized as the most advantageous next-generation anode material for LIBs in terms of its extremely high theoretical capacity and appropriate operating voltage.However,the application of Si anode is limited by huge volume expansion emerging with cycling,which in turn induces the collapse of the electrode structure,resulting in rapid capacity decay.Here,we report a strategy using self-swelling artificial laponite to prepare a laponite/MXene/CNT composite framework with both rigidity and flexibility,which can excellently address these challenges of Si anode.The self-swelling artificial laponite participates in the construction of hierarchical and porous structures,providing sufficient buffer space to mitigate the volume expansion of the LixSi alloying reaction.Meanwhile,tough and tightly cross-linked silicate nanosheets can improve the mechanical strength of the framework for strong structural stability.More importantly,the negative charge between the layers of artificial laponite can effectively promote fast Li-ion transport in the electrode.This free-standing silicon anode enables the preparation of high areal capacity electrodes to further enhance the energy density of LIBs and a higher reversible capacity of 2381.8 mAh/g at 0.1 C after 50 cycles with an initial coulombic of 85.6%.This work provides a simple and practical fabrication strategy for developing high-performance Si-based batteries,which can speed up their commercialization.
