The magnetic perovskite-supported palladium catalysts Pd/Lal_xPbxMnO3 （x = 0.2-0.7） were prepared and used for the oxidative carbonylation of phenol to diphenyl carbonate. The synthesized catalysts were characterize...The magnetic perovskite-supported palladium catalysts Pd/Lal_xPbxMnO3 （x = 0.2-0.7） were prepared and used for the oxidative carbonylation of phenol to diphenyl carbonate. The synthesized catalysts were characterized by the X-ray diffraction （XRD）, surface area measurement BET, vibration sample magnetometer （VSM） and tem- perature-programmed reduction （TPR）. The experimental results demonstrated that the magnetic Pd/La1-xPbxMnO3 （x = 0.4-0.5） obtain relative better catalytic activity. It can be explained by higher concentration of oxygen vacan- cies, larger amount and better mobility of lattice oxygen of their support. Furthermore, these samples possess suffi- cient saturated magnetization. Thus, Pd/La1-xPbxMnO3 （x = 0.4-0.5） may be suitable for operation in the magneti- cally stabilized bed reactor.展开更多
In the era of serious greenhouse gas emission and energy shortage,it is necessary to use solid waste to prepare new renewable materials.In this work,the potential application of reed straw and electric furnace dust wa...In the era of serious greenhouse gas emission and energy shortage,it is necessary to use solid waste to prepare new renewable materials.In this work,the potential application of reed straw and electric furnace dust was explored.Firstly,magnetic carbon carrier(EFD&C)was prepared by high temperature calcination,and then magnetic carbon catalyst(SM@EFD&C)was prepared by activation of sodium methoxide.The catalyst was used to prepare biodiesel by transesterification reaction to test its activity and stability.Reed biochar,EFD&C and SM@EFD&C were detected by Diffraction of X-rays(XRD),Fourier transform infrared(FT-IR),Inductively coupled plasma(ICP),Scanning electron microscope(SEM),Transmission electron microscope(TEM),Brunauer-Emmett-Teller(BET),Vibrating sample magnetometer(VSM),Temperature programmed desorption of CO_(2)(CO_(2)-TPD)and Thermogravimetric analysis(TG-DTG).The results showed that SM@EFD&C catalyst had some characteristics including porous structure,easy adsorption and better magnetism.Under the reaction conditions of 65℃for 2 h with 6 wt%catalyst and methanol/oil molar ratio of 15:1,the biodiesel yields from reed biochar and EFD&C were only 4.88 wt%and 0.03 wt%,respectively,while the yield from SM@EFD&C catalyst reached 93.14 wt%(89.84 wt%after 7 cycles)under the same conditions,which proved that it had good catalytic activity and stability when used in biodiesel production.This study is of great significance of carbon dioxide emission reduction and environmental protection.展开更多
An efficient route for the synthesis of 5-substituted 1H-tetrazole via[2＋3]cycloaddition of nitriles and sodium azide is reported usingγ-Fe2O3 nanoparticles as a magnetic separable catalyst.Under optimized condition...An efficient route for the synthesis of 5-substituted 1H-tetrazole via[2＋3]cycloaddition of nitriles and sodium azide is reported usingγ-Fe2O3 nanoparticles as a magnetic separable catalyst.Under optimized conditions,the moderate to good yields（71-95%） can be obtained.The catalyst can be easily separated by a magnet and reused for several circles.展开更多
A novel magnetically recoverable thioporphyrazine catalyst（CoPz（S-Bu）8/SiO2@Fe3O4） was prepared by immobilization of the cobalt octkis（butylthio） porphyrazine complex（CoPz（S-Bu）8） on silica-coated magnetic n...A novel magnetically recoverable thioporphyrazine catalyst（CoPz（S-Bu）8/SiO2@Fe3O4） was prepared by immobilization of the cobalt octkis（butylthio） porphyrazine complex（CoPz（S-Bu）8） on silica-coated magnetic nanospheres（SiO2@Fe3O4）. The composite CoPz（S-Bu）8/SiO2@Fe3O4appeared to be an active catalyst in the oxidation of benzyl alcohol in aqueous solution using hydrogen peroxide（H2O2） as oxidant under Xe-lamp irradiation,with 36.4% conversion of benzyl alcohol, about 99% selectivity for benzoic acid and turnover number（TON） of 61.7 at ambient temperature. The biomimetic catalyst CoPz（S-Bu）8was supported on the magnetic carrier SiO2@Fe3O4 so as to suspend it in aqueous solution to react with substrates, utilizing its lipophilicity. Meanwhile the CoPz（S-Bu）8can use its unique advantages to control the selectivity of photocatalytic oxidation without the substrate being subjected to deep oxidation. The influence of various reaction parameters on the conversion rate of benzyl alcohol and selectivity of benzoic acid was investigated in detail. Moreover, photocatalytic oxidation of substituted benzyl alcohols was obtained with high conversion and excellent selectivity, specifically conversion close to 70%, selectivity close to 100% and TON of 113.6 for para-position electron-donating groups. The selectivity and eco-friendliness of the biomimetic photocatalyst give it great potential for practical applications.展开更多
Owing to outstanding hydrophilicity and ionic interaction,layered double hydroxides(LDHs)have emerged as a promising carrier for high performance catalysts.However,the synthesis of new specialized catalytic LDHs for d...Owing to outstanding hydrophilicity and ionic interaction,layered double hydroxides(LDHs)have emerged as a promising carrier for high performance catalysts.However,the synthesis of new specialized catalytic LDHs for degradation of antibiotics still faces some challenges.In this study,a CoFe_(2)O_(4)/MgAl-LDH composite catalyst was synthesized using a hydrothermal coprecipitation method.Comprehensive characterization reveals that the surface of MgAl-LDH is covered with nanometer CoFe_(2)O_(4) particles.The specific surface area of CoFe_(2)O_(4)/MgAl-LDH is 82.84 m^(2)·g^(-)1,which is 2.34 times that of CoFe_(2)O_(4).CoFe_(2)O_(4)/MgAl-LDH has a saturation magnetic strength of 22.24 A·m^(2)·kg^(-1) facilitating efficient solid-liquid separation.The composite catalyst was employed to activate peroxymonosulfate(PMS)for the efficient degradation of tetracycline hydrochloride(TCH).It is found that the catalytic performance of CoFe_(2)O_(4)/MgAl-LDH significantly exceeds that of CoFe_(2)O_(4).The maximum TCH removal reaches 98.2%under the optimal conditions([TCH]=25 mg/L,[PMS]=1.5 mmol/L,CoFe_(2)O_(4)/MgAl-LDH=0.20 g/L,pH 7,and T=25℃).Coexisting ions in the solution,such as SO_(4)^(2-),Cl-,H_(2)PO_(4)^(-),and CO_(3)^(2-),have a negligible effect on catalytic performance.Cyclic tests demonstrate that the catalytic performance of CoFe_(2)O_(4)/MgAl-LDH remains 67.2%after five cycles.Mechanism investigations suggest that O_(2)^(•-)and ^(1)O_(2) produced by CoFe_(2)O_(4)/MgAl-LDH play a critical role in the catalytic degradation.展开更多
The bimetallic nanoparticles compositing of Ni-rich core and Cu-rich shell(Ni/Cu NPs)were successfully synthesized by a liquid-phase thermal decomposition method.The content of copper and nickel in Ni/Cu NPs was contr...The bimetallic nanoparticles compositing of Ni-rich core and Cu-rich shell(Ni/Cu NPs)were successfully synthesized by a liquid-phase thermal decomposition method.The content of copper and nickel in Ni/Cu NPs was controllable by adjusting the ratio of two metal precursors,copper formate(Cuf)and nickel acetate tetrahydrate(Ni(OAc)_(2)·4H_(2)O).Ni/Cu NPs were further anchored on graphene oxide(GO)to prepare a magnetic composite catalyst,called Ni/Cu-GO.The dispersibility of Ni/Cu NPs in solution was enhanced by GO anchoring to prevent the sintering and aggregation during the reaction process,thereby ensuring the catalytic and cycling performance of the catalyst.The catalytic transfer hydrogenation(CTH)reaction of nitroaromatics was investigated when ammonia borane was used as the hydrogen source.Cu dominated the main catalytic role in the reaction,while Ni played a synergistic role of catalysis and providing magnetic properties for separation.The Ni_(7)/Cu_(3)-GO catalyst exhibited the best catalytic performance with the conversion and yield of 99%and 96%,respectively,when 2-methyl-5-nitrophenol was used as the substrate.The Ni_(7)/Cu_(3)-GO catalyst also exhibited excellent cyclic catalytic performance with the 5-amino-2-methylphenol yield of above 90%after six cycles.In addition,the Ni_(7)/Cu_(3)-GO catalyst could be quickly recycled by magnetic separation.Moreover,the Ni_(7)/Cu_(3)-GO catalyst showed good catalytic performance for halogen-containing nitroaromatics without dehalogenation.展开更多
The base-free aerobic oxidation of 5-hydroxymethylfurfural(HMF) to 2,5-furandicarboxylic acid(FDCA)in water is recognized as an important and sustainable upgrading process for cellulosic carbohydrates.However,selectiv...The base-free aerobic oxidation of 5-hydroxymethylfurfural(HMF) to 2,5-furandicarboxylic acid(FDCA)in water is recognized as an important and sustainable upgrading process for cellulosic carbohydrates.However,selectivity control still remains a challenge.Here,we disclose that the unique synergy in magnetic Ni_(x)Co_(1)O_(y)(x=1,3 and 5) bimetallic oxides can induce reactive oxygen defects and simultaneously stabilize small-sized metallic Au nanoparticles in the Au/Ni_(x)Co_(1)O_(y)catalysts.Such catalytic features render effective adsorption and activation of O_(2),OH and C=O groups,realizing selective oxidation of HMF to FDCA.On a series of magnetic Au/Ni_(x)Co_(1)O_(y)catalysts with almost identical Au loadings(ca.0.5 wt%) and particle sizes(ca.2.7 nm),the variable Ni/Co molar ratios give rise to the tunable electron density of Au sites and synergistic effect between NiO and CoO_(y).The initial conversion rates of HMF and its derived intermediates(i.e., DFF,HMFCA and FFCA) show a volcano-like dependence on the number of oxygen defects(i.e.,O_(2)^(-)and O^(-)) and electron-rich Au0sites.The optimum Au/Ni3Co1Oycatalyst exhibits a highest productivity of FDCA(12.5 mmol_(FDCA)mol_(Au)^(-1)h^(-1)) among all the Au catalysts in the literature and achieves> 99% yield of FDCA at 120℃ and 10 bar of O_(2).In addition,this catalyst can be easily recovered by a magnet and show superior stability and reusability during six consecutive cycling tests.This work may shed a light on Au catalysis for the base-free oxidation of biomass compounds by smartly using the synergy in bimetallic oxide carriers.展开更多
separation is an attractive alternative to filtration or centrifugation for separating solid catalysts from a liquid phase, Here, core-shell Fe3O4@UiO-66-NH2 nanohybrids with well-defined structures were constructed b...separation is an attractive alternative to filtration or centrifugation for separating solid catalysts from a liquid phase, Here, core-shell Fe3O4@UiO-66-NH2 nanohybrids with well-defined structures were constructed by dispersing magnets in a dimethylformamide （DMF） solution con- taining two metal-organic framework （MOF） precursors, namely ZrCI4 and 2-aminobenzenetricar- boxylic acid. This method is simpler and more efficient than previously reported step-by-step method in which magnets were consecutively dispersed in DMF solutions each containing one MOF precursor, and the obtained Fe304@UiO-66-NH2 with three assembly cycles has a higher degree of crystallinity and porosiW. The core-shell Fe3O4@UiO-66-NH2 is highly active and selective in Knoevenagel condensations because of the bifunctionality of UiO-66-NH2 and better mass transfer in the nano-sized shells. It also has good recycling stability, and can be recovered magnetically and reused at least four times without significant loss of catalytic activity and framework integrity. The effects of substitution on the reactivity of benzaldehyde and of substrate size were also investigated.展开更多
The effects of cation ordering and surface compensating anions on the magnetic structure and catalytic properties of unilamellar Ni-Fe hydroxide nanosheets are studied by using the density functional theory （DFT） pl...The effects of cation ordering and surface compensating anions on the magnetic structure and catalytic properties of unilamellar Ni-Fe hydroxide nanosheets are studied by using the density functional theory （DFT） plus U method. Fe-segregation in the nanosheets yields magnetic domains with different spin alignments, while the surface compensating anions affect the local moments and valence states of the Fe atoms. The two conditions do not radically change the super-exchange nature of interactions between the paramagnetic metal centers, hut facilitate the formation of various magnetic superlattices in the nanosheets. The calculated free energy change of the intermediates shows that the most stable magnetic structure of Ni-Fe hydrox- ide nanosheets exhibits superior catalytic activity towards oxygen reduction/evolution reactions, which is indicative of magnetic catalyst. This is due to the cycle transition between Fe2＋ and Fe~~ ions in the reactions, which determines the sequence of cleavage of the O-H bond and the release of the OH group, controlling the rate-limiting steps of the reaction. The relationship of magnetism and catalytic activity of Ni-Fe hydroxide nanosheets is established by the valence state change of the Fe ions, which will be helpful to open the way for the design of hydroxide/layered double hydroxides （LDHs）-based magnetic catalysts.展开更多
Abstract Heterogeneous catalysts with convenient recyclability and reusability are vitally important to reduce the cost of catalysts as well as to avoid complex separation and recovery operations. In this regard, magn...Abstract Heterogeneous catalysts with convenient recyclability and reusability are vitally important to reduce the cost of catalysts as well as to avoid complex separation and recovery operations. In this regard, magnetic MIL-100 （Fe）@SiO2@Fe3O4 microspheres with a novel core-shell structure were fabricated by the in-situ self-assembly of a metal-organic MIL- 100（Fe） framework around pre-synthesized magnetic SiO2@Fe3O4 particles under relatively mild and environmentally benign conditions. The catalytic activity of the MIL-100（Fe）@SiO2@Fe3O4 catalyst was tested for the liquid-phase acetalization of benzaldehyde and glycol. The MIL-100（Fe）@SiO2@Fe3O4 catalyst has a significant amount of accessible Lewis acid sites and therefore exhibited good acetalization catalytic activity. Moreover, due to its superparamagnetism properties, the heterogeneous MIL-100（Fe）@SiO2@Fe3O4 catalyst can be easily isolated from the reaction system within a few seconds by simply using an external magnet. The catalyst could then be reused at least eight times without significant loss in catalytic efficiency.展开更多
A straightforward and general method has been developed for the synthesis of C5-unsubstitiuted 1,4-dihydropyridines by a reaction using dimedone, acetophenone, aromatic aldehydes, and ammonium acetate in the presence ...A straightforward and general method has been developed for the synthesis of C5-unsubstitiuted 1,4-dihydropyridines by a reaction using dimedone, acetophenone, aromatic aldehydes, and ammonium acetate in the presence of a catalytic amount of Co nanoparticles as a heterogeneous and eco-friendly catalyst with high catalytic activity at room temperature under solvent-free conditions. This catalyst is easily separated by magnetic devices and can be reused without any apparent loss of activity for the reaction. In addition, it is very interesting that when using Co nanoparticles as a catalyst, spatially-hindered aldehydes such as 2-methoxy-, 2-fluoro-, and 2-chloro-aldehydes are suitable for this reaction.展开更多
Highly active and stable magnetic copper catalysts were successfully achieved by magnetic induced Stober method and subsequent hydrothermal reaction with copper ions in alkaline condition.The high content of Cu2+as we...Highly active and stable magnetic copper catalysts were successfully achieved by magnetic induced Stober method and subsequent hydrothermal reaction with copper ions in alkaline condition.The high content of Cu2+as well as the unique structures of hierarchical copper silicate in the as-prepared catalysts endowed their outstanding catalytic performance.Efficient decarboxylative A3-coupling of a-keto acid,amine and alkyne was realized with the low Fe3 O4@CuSiO3 loading.A range of propargylamines were produced in good to excellent yields under solvent-free condition.Moreover,the catalyst can be easily separated from the final organic product with an external magnet.Also,this kind of catalyst could be recycled up to six times while maintaining its activity.展开更多
In recent years,persulfate(PS)-based advanced oxidation processes(AOPs)have become a hot research topic for degrading environmental pollutants due to their excellent oxidation capacity,selectivity,and stability.PS-AOP...In recent years,persulfate(PS)-based advanced oxidation processes(AOPs)have become a hot research topic for degrading environmental pollutants due to their excellent oxidation capacity,selectivity,and stability.PS-AOPs can generate sulfate radicals(SO^(·-)_(4))with strong oxidation ability,but single PS produces limited or no radicals.Therefore,activation of PS by energy input or catalyst dosing is used to improve its oxidation performance.However,the addition of disposable catalyst not only causes a waste of resources,but also may lead to secondary pollution.Therefore,magnetically separable catalysts for activating PS have received widespread attention due to their reusability.Although there are few literature reviews on the activation of PS by carbon-or iron-based magnetic materials,the mechanism analysis of the activation of PS by magnetic materials to degrade pollut-ants is not deep enough,and the discussion of material types is not comprehensive and detailed.Moreover,the discussion of magnetic materials in terms of recycling properties is lacking.Therefore,this review firstly sum-marizes and analyzes the mechanism of magnetically separable catalysts activating PS to degrade pollutants.Then,the research progress of zero-valent iron(ZVI,Fe^(0))-based,iron oxide-based,bimetallic oxide-based,and other magnetically separable catalyst is introduced,and the tailoring engineering approaches and reusability of magnetically separable catalysts are discussed.Finally,some possible material optimization suggestions are proposed in this paper.In conclusion,this review is expected to provide useful insights for improving the per-formance and reusability of magnetically separable materials activated PS in the future.展开更多
The electrocatalysis reactions involving oxygen,such as oxygen evolution reaction(OER)and oxygen reduction reaction(ORR),play a critical role in energy storage/conversion applications,e.g.,fuel cells,metal-air batteri...The electrocatalysis reactions involving oxygen,such as oxygen evolution reaction(OER)and oxygen reduction reaction(ORR),play a critical role in energy storage/conversion applications,e.g.,fuel cells,metal-air batteries,and electrochemical water splitting.The high kinetic energy barrier of the OER/ORR is highly associated with the spin state interconversion between singlet OH^(−)/H_(2)O and triplet O_(2),which is influenced by the spin state and magnetism of catalysts.This Review summarizes recent progress and advances in understanding spin/magnetism-related effects in oxygen electrocatalysis to develop spin theory.It is demonstrated that the spin states(low,intermediate,and high spin)of magnetic transition metal catalysts(TMCs)can directly affect the reaction barriers of OER/ORR by tailoring the bonding of oxygen intermediates with TMCs.Besides,the spin states of TMCs can build a spin-selective channel to filter the electron spins required for the single/triplet interconversion of O species during OER/ORR.In this Review,we introduced many approaches to modulating spin state,for instance,altering the crystal field,oxidation state of active-site ions,and the morphology of TMCs.What’s more,a magnetic field can drive the spin flip of magnetic ions to achieve the spin alignment(↑↑)(i.e.,facilitating spin polarization),which will strengthen the spin selectivity for accelerating the filtration and transfer of the spins with the same direction for the generation and conversion of triplet ↑O=O↑.Importantly,the origin of magnetic field enhancement on OER/ORR are deeply discussed,which provides a great vision for the magnetism-assisted catalysis.Finally,the challenges and perspectives for future development of spin/magnetism catalysis are presented.This Review is expected to highlight the significance of spin/magnetism theory in breaking the bottleneck of electrocatalysis field and promote the development of high-efficientcy electrocatalysts for practical applications.展开更多
基金Supported by the Key Program of National Natural Science Foundation of China(20936003)the Foundation for Innovation Research Groups of the Natural Science Foundation of Hubei Province(2008CDA009)
文摘The magnetic perovskite-supported palladium catalysts Pd/Lal_xPbxMnO3 （x = 0.2-0.7） were prepared and used for the oxidative carbonylation of phenol to diphenyl carbonate. The synthesized catalysts were characterized by the X-ray diffraction （XRD）, surface area measurement BET, vibration sample magnetometer （VSM） and tem- perature-programmed reduction （TPR）. The experimental results demonstrated that the magnetic Pd/La1-xPbxMnO3 （x = 0.4-0.5） obtain relative better catalytic activity. It can be explained by higher concentration of oxygen vacan- cies, larger amount and better mobility of lattice oxygen of their support. Furthermore, these samples possess suffi- cient saturated magnetization. Thus, Pd/La1-xPbxMnO3 （x = 0.4-0.5） may be suitable for operation in the magneti- cally stabilized bed reactor.
基金the financial support from National Natural Science Foundation of China(Nos:52004095,51704119,and 21878161)the Natural Science Foundation of Hebei Province(E2017209243)Department of Education of Hebei Province(BJ2019038).
文摘In the era of serious greenhouse gas emission and energy shortage,it is necessary to use solid waste to prepare new renewable materials.In this work,the potential application of reed straw and electric furnace dust was explored.Firstly,magnetic carbon carrier(EFD&C)was prepared by high temperature calcination,and then magnetic carbon catalyst(SM@EFD&C)was prepared by activation of sodium methoxide.The catalyst was used to prepare biodiesel by transesterification reaction to test its activity and stability.Reed biochar,EFD&C and SM@EFD&C were detected by Diffraction of X-rays(XRD),Fourier transform infrared(FT-IR),Inductively coupled plasma(ICP),Scanning electron microscope(SEM),Transmission electron microscope(TEM),Brunauer-Emmett-Teller(BET),Vibrating sample magnetometer(VSM),Temperature programmed desorption of CO_(2)(CO_(2)-TPD)and Thermogravimetric analysis(TG-DTG).The results showed that SM@EFD&C catalyst had some characteristics including porous structure,easy adsorption and better magnetism.Under the reaction conditions of 65℃for 2 h with 6 wt%catalyst and methanol/oil molar ratio of 15:1,the biodiesel yields from reed biochar and EFD&C were only 4.88 wt%and 0.03 wt%,respectively,while the yield from SM@EFD&C catalyst reached 93.14 wt%(89.84 wt%after 7 cycles)under the same conditions,which proved that it had good catalytic activity and stability when used in biodiesel production.This study is of great significance of carbon dioxide emission reduction and environmental protection.
基金the Jiangsu Province Foundation of Natural Science(No.BK2009678) for the financial support
文摘An efficient route for the synthesis of 5-substituted 1H-tetrazole via[2＋3]cycloaddition of nitriles and sodium azide is reported usingγ-Fe2O3 nanoparticles as a magnetic separable catalyst.Under optimized conditions,the moderate to good yields（71-95%） can be obtained.The catalyst can be easily separated by a magnet and reused for several circles.
基金supported by the National Natural Science Foundation of China (Nos. 21272281 and 20977115)Natural Science Foundation of Hubei Province (2014CFB919)+1 种基金"the Fundamental Research Funds for the Central Universities", South-Central University for Nationalities (CZY14003)the Science and Technology Plan Innovation Team of Wuhan City (2015070504020220)
文摘A novel magnetically recoverable thioporphyrazine catalyst（CoPz（S-Bu）8/SiO2@Fe3O4） was prepared by immobilization of the cobalt octkis（butylthio） porphyrazine complex（CoPz（S-Bu）8） on silica-coated magnetic nanospheres（SiO2@Fe3O4）. The composite CoPz（S-Bu）8/SiO2@Fe3O4appeared to be an active catalyst in the oxidation of benzyl alcohol in aqueous solution using hydrogen peroxide（H2O2） as oxidant under Xe-lamp irradiation,with 36.4% conversion of benzyl alcohol, about 99% selectivity for benzoic acid and turnover number（TON） of 61.7 at ambient temperature. The biomimetic catalyst CoPz（S-Bu）8was supported on the magnetic carrier SiO2@Fe3O4 so as to suspend it in aqueous solution to react with substrates, utilizing its lipophilicity. Meanwhile the CoPz（S-Bu）8can use its unique advantages to control the selectivity of photocatalytic oxidation without the substrate being subjected to deep oxidation. The influence of various reaction parameters on the conversion rate of benzyl alcohol and selectivity of benzoic acid was investigated in detail. Moreover, photocatalytic oxidation of substituted benzyl alcohols was obtained with high conversion and excellent selectivity, specifically conversion close to 70%, selectivity close to 100% and TON of 113.6 for para-position electron-donating groups. The selectivity and eco-friendliness of the biomimetic photocatalyst give it great potential for practical applications.
基金University Synergy Innovation Program of Anhui Province(GXXT-2022-083)Science and Technology Plan Project of Wuhu City,China(2023kx12)Anhui Provincial Department of Education New Era Education Project(2023xscx070)。
文摘Owing to outstanding hydrophilicity and ionic interaction,layered double hydroxides(LDHs)have emerged as a promising carrier for high performance catalysts.However,the synthesis of new specialized catalytic LDHs for degradation of antibiotics still faces some challenges.In this study,a CoFe_(2)O_(4)/MgAl-LDH composite catalyst was synthesized using a hydrothermal coprecipitation method.Comprehensive characterization reveals that the surface of MgAl-LDH is covered with nanometer CoFe_(2)O_(4) particles.The specific surface area of CoFe_(2)O_(4)/MgAl-LDH is 82.84 m^(2)·g^(-)1,which is 2.34 times that of CoFe_(2)O_(4).CoFe_(2)O_(4)/MgAl-LDH has a saturation magnetic strength of 22.24 A·m^(2)·kg^(-1) facilitating efficient solid-liquid separation.The composite catalyst was employed to activate peroxymonosulfate(PMS)for the efficient degradation of tetracycline hydrochloride(TCH).It is found that the catalytic performance of CoFe_(2)O_(4)/MgAl-LDH significantly exceeds that of CoFe_(2)O_(4).The maximum TCH removal reaches 98.2%under the optimal conditions([TCH]=25 mg/L,[PMS]=1.5 mmol/L,CoFe_(2)O_(4)/MgAl-LDH=0.20 g/L,pH 7,and T=25℃).Coexisting ions in the solution,such as SO_(4)^(2-),Cl-,H_(2)PO_(4)^(-),and CO_(3)^(2-),have a negligible effect on catalytic performance.Cyclic tests demonstrate that the catalytic performance of CoFe_(2)O_(4)/MgAl-LDH remains 67.2%after five cycles.Mechanism investigations suggest that O_(2)^(•-)and ^(1)O_(2) produced by CoFe_(2)O_(4)/MgAl-LDH play a critical role in the catalytic degradation.
基金supported by the National Natural Science Foundation of China(Grant No.21776161)。
文摘The bimetallic nanoparticles compositing of Ni-rich core and Cu-rich shell(Ni/Cu NPs)were successfully synthesized by a liquid-phase thermal decomposition method.The content of copper and nickel in Ni/Cu NPs was controllable by adjusting the ratio of two metal precursors,copper formate(Cuf)and nickel acetate tetrahydrate(Ni(OAc)_(2)·4H_(2)O).Ni/Cu NPs were further anchored on graphene oxide(GO)to prepare a magnetic composite catalyst,called Ni/Cu-GO.The dispersibility of Ni/Cu NPs in solution was enhanced by GO anchoring to prevent the sintering and aggregation during the reaction process,thereby ensuring the catalytic and cycling performance of the catalyst.The catalytic transfer hydrogenation(CTH)reaction of nitroaromatics was investigated when ammonia borane was used as the hydrogen source.Cu dominated the main catalytic role in the reaction,while Ni played a synergistic role of catalysis and providing magnetic properties for separation.The Ni_(7)/Cu_(3)-GO catalyst exhibited the best catalytic performance with the conversion and yield of 99%and 96%,respectively,when 2-methyl-5-nitrophenol was used as the substrate.The Ni_(7)/Cu_(3)-GO catalyst also exhibited excellent cyclic catalytic performance with the 5-amino-2-methylphenol yield of above 90%after six cycles.In addition,the Ni_(7)/Cu_(3)-GO catalyst could be quickly recycled by magnetic separation.Moreover,the Ni_(7)/Cu_(3)-GO catalyst showed good catalytic performance for halogen-containing nitroaromatics without dehalogenation.
基金supported by the National Natural Science Foundation of China(22272149,22062025,21763031)the Yunnan Fundamental Research Projects(202001AW070012,202101AT070171)+3 种基金the Yunnan University’s Research Innovation Fund for Graduate Students(KC-22221892)the Open Research Fund of School of Chemistry and Chemical Engineering of Henan Normal Universitythe Workstation of Academician Chen Jing of Yunnan Province(202105AF150012)the Free Exploration Fund for Academician(202205AA160007)。
文摘The base-free aerobic oxidation of 5-hydroxymethylfurfural(HMF) to 2,5-furandicarboxylic acid(FDCA)in water is recognized as an important and sustainable upgrading process for cellulosic carbohydrates.However,selectivity control still remains a challenge.Here,we disclose that the unique synergy in magnetic Ni_(x)Co_(1)O_(y)(x=1,3 and 5) bimetallic oxides can induce reactive oxygen defects and simultaneously stabilize small-sized metallic Au nanoparticles in the Au/Ni_(x)Co_(1)O_(y)catalysts.Such catalytic features render effective adsorption and activation of O_(2),OH and C=O groups,realizing selective oxidation of HMF to FDCA.On a series of magnetic Au/Ni_(x)Co_(1)O_(y)catalysts with almost identical Au loadings(ca.0.5 wt%) and particle sizes(ca.2.7 nm),the variable Ni/Co molar ratios give rise to the tunable electron density of Au sites and synergistic effect between NiO and CoO_(y).The initial conversion rates of HMF and its derived intermediates(i.e., DFF,HMFCA and FFCA) show a volcano-like dependence on the number of oxygen defects(i.e.,O_(2)^(-)and O^(-)) and electron-rich Au0sites.The optimum Au/Ni3Co1Oycatalyst exhibits a highest productivity of FDCA(12.5 mmol_(FDCA)mol_(Au)^(-1)h^(-1)) among all the Au catalysts in the literature and achieves> 99% yield of FDCA at 120℃ and 10 bar of O_(2).In addition,this catalyst can be easily recovered by a magnet and show superior stability and reusability during six consecutive cycling tests.This work may shed a light on Au catalysis for the base-free oxidation of biomass compounds by smartly using the synergy in bimetallic oxide carriers.
基金supported by the National Natural Science Foundation of China (21203017)Open Fund of State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences (N-11-3)+1 种基金Program for Liaoning Excellent Talents in University (LNET)the Funda-mental Research Funds for the Central Universities (DC201502020304)~~
文摘separation is an attractive alternative to filtration or centrifugation for separating solid catalysts from a liquid phase, Here, core-shell Fe3O4@UiO-66-NH2 nanohybrids with well-defined structures were constructed by dispersing magnets in a dimethylformamide （DMF） solution con- taining two metal-organic framework （MOF） precursors, namely ZrCI4 and 2-aminobenzenetricar- boxylic acid. This method is simpler and more efficient than previously reported step-by-step method in which magnets were consecutively dispersed in DMF solutions each containing one MOF precursor, and the obtained Fe304@UiO-66-NH2 with three assembly cycles has a higher degree of crystallinity and porosiW. The core-shell Fe3O4@UiO-66-NH2 is highly active and selective in Knoevenagel condensations because of the bifunctionality of UiO-66-NH2 and better mass transfer in the nano-sized shells. It also has good recycling stability, and can be recovered magnetically and reused at least four times without significant loss of catalytic activity and framework integrity. The effects of substitution on the reactivity of benzaldehyde and of substrate size were also investigated.
基金supported by the National Natural Science Foundation of China (21431003)the National Program on Key Basic Research Project (2014CB932101)the Fundamental Research Funds for the Central Universities (buctrc201514)
文摘The effects of cation ordering and surface compensating anions on the magnetic structure and catalytic properties of unilamellar Ni-Fe hydroxide nanosheets are studied by using the density functional theory （DFT） plus U method. Fe-segregation in the nanosheets yields magnetic domains with different spin alignments, while the surface compensating anions affect the local moments and valence states of the Fe atoms. The two conditions do not radically change the super-exchange nature of interactions between the paramagnetic metal centers, hut facilitate the formation of various magnetic superlattices in the nanosheets. The calculated free energy change of the intermediates shows that the most stable magnetic structure of Ni-Fe hydrox- ide nanosheets exhibits superior catalytic activity towards oxygen reduction/evolution reactions, which is indicative of magnetic catalyst. This is due to the cycle transition between Fe2＋ and Fe~~ ions in the reactions, which determines the sequence of cleavage of the O-H bond and the release of the OH group, controlling the rate-limiting steps of the reaction. The relationship of magnetism and catalytic activity of Ni-Fe hydroxide nanosheets is established by the valence state change of the Fe ions, which will be helpful to open the way for the design of hydroxide/layered double hydroxides （LDHs）-based magnetic catalysts.
基金Acknowledgements This work was supported by the National Natural Science Foundation of China （Grant No. 21576243） and the Public Project of Zhejiang Province of China （2016C37057）.
文摘Abstract Heterogeneous catalysts with convenient recyclability and reusability are vitally important to reduce the cost of catalysts as well as to avoid complex separation and recovery operations. In this regard, magnetic MIL-100 （Fe）@SiO2@Fe3O4 microspheres with a novel core-shell structure were fabricated by the in-situ self-assembly of a metal-organic MIL- 100（Fe） framework around pre-synthesized magnetic SiO2@Fe3O4 particles under relatively mild and environmentally benign conditions. The catalytic activity of the MIL-100（Fe）@SiO2@Fe3O4 catalyst was tested for the liquid-phase acetalization of benzaldehyde and glycol. The MIL-100（Fe）@SiO2@Fe3O4 catalyst has a significant amount of accessible Lewis acid sites and therefore exhibited good acetalization catalytic activity. Moreover, due to its superparamagnetism properties, the heterogeneous MIL-100（Fe）@SiO2@Fe3O4 catalyst can be easily isolated from the reaction system within a few seconds by simply using an external magnet. The catalyst could then be reused at least eight times without significant loss in catalytic efficiency.
基金supported by the University Grants Commission, University of Kashan
文摘A straightforward and general method has been developed for the synthesis of C5-unsubstitiuted 1,4-dihydropyridines by a reaction using dimedone, acetophenone, aromatic aldehydes, and ammonium acetate in the presence of a catalytic amount of Co nanoparticles as a heterogeneous and eco-friendly catalyst with high catalytic activity at room temperature under solvent-free conditions. This catalyst is easily separated by magnetic devices and can be reused without any apparent loss of activity for the reaction. In addition, it is very interesting that when using Co nanoparticles as a catalyst, spatially-hindered aldehydes such as 2-methoxy-, 2-fluoro-, and 2-chloro-aldehydes are suitable for this reaction.
基金supported by the National Natural Science Foundation of China(Nos.21601121,21305086)the Natural Science Foundation of Shanghai(No.18ZR1416400)+1 种基金support of the Shanghai University of Engineering Science(Nos.201810856017,A1-0601-19-01017)the Opening Project of Shanghai Key Laboratory of Chemical Biology for financial support。
文摘Highly active and stable magnetic copper catalysts were successfully achieved by magnetic induced Stober method and subsequent hydrothermal reaction with copper ions in alkaline condition.The high content of Cu2+as well as the unique structures of hierarchical copper silicate in the as-prepared catalysts endowed their outstanding catalytic performance.Efficient decarboxylative A3-coupling of a-keto acid,amine and alkyne was realized with the low Fe3 O4@CuSiO3 loading.A range of propargylamines were produced in good to excellent yields under solvent-free condition.Moreover,the catalyst can be easily separated from the final organic product with an external magnet.Also,this kind of catalyst could be recycled up to six times while maintaining its activity.
基金supported by the National Natural Science Foundation of China(No.51508228)Guangdong Basic and Applied Basic Research Foundation(No.2021A1515011804)+1 种基金Zhongshan Social Public Welfare and Basic Research Project(No.210723154031576)the Fundamental Research Funds for the Central Universities.
文摘In recent years,persulfate(PS)-based advanced oxidation processes(AOPs)have become a hot research topic for degrading environmental pollutants due to their excellent oxidation capacity,selectivity,and stability.PS-AOPs can generate sulfate radicals(SO^(·-)_(4))with strong oxidation ability,but single PS produces limited or no radicals.Therefore,activation of PS by energy input or catalyst dosing is used to improve its oxidation performance.However,the addition of disposable catalyst not only causes a waste of resources,but also may lead to secondary pollution.Therefore,magnetically separable catalysts for activating PS have received widespread attention due to their reusability.Although there are few literature reviews on the activation of PS by carbon-or iron-based magnetic materials,the mechanism analysis of the activation of PS by magnetic materials to degrade pollut-ants is not deep enough,and the discussion of material types is not comprehensive and detailed.Moreover,the discussion of magnetic materials in terms of recycling properties is lacking.Therefore,this review firstly sum-marizes and analyzes the mechanism of magnetically separable catalysts activating PS to degrade pollutants.Then,the research progress of zero-valent iron(ZVI,Fe^(0))-based,iron oxide-based,bimetallic oxide-based,and other magnetically separable catalyst is introduced,and the tailoring engineering approaches and reusability of magnetically separable catalysts are discussed.Finally,some possible material optimization suggestions are proposed in this paper.In conclusion,this review is expected to provide useful insights for improving the per-formance and reusability of magnetically separable materials activated PS in the future.
基金financially supported by the National Natural Science Foundation of China(Grants No.52027801,52111530236)the National Postdoctoral Program for Innovative Talents(BX20220002)China Postdoctoral Science Foundation(2022M720204).
文摘The electrocatalysis reactions involving oxygen,such as oxygen evolution reaction(OER)and oxygen reduction reaction(ORR),play a critical role in energy storage/conversion applications,e.g.,fuel cells,metal-air batteries,and electrochemical water splitting.The high kinetic energy barrier of the OER/ORR is highly associated with the spin state interconversion between singlet OH^(−)/H_(2)O and triplet O_(2),which is influenced by the spin state and magnetism of catalysts.This Review summarizes recent progress and advances in understanding spin/magnetism-related effects in oxygen electrocatalysis to develop spin theory.It is demonstrated that the spin states(low,intermediate,and high spin)of magnetic transition metal catalysts(TMCs)can directly affect the reaction barriers of OER/ORR by tailoring the bonding of oxygen intermediates with TMCs.Besides,the spin states of TMCs can build a spin-selective channel to filter the electron spins required for the single/triplet interconversion of O species during OER/ORR.In this Review,we introduced many approaches to modulating spin state,for instance,altering the crystal field,oxidation state of active-site ions,and the morphology of TMCs.What’s more,a magnetic field can drive the spin flip of magnetic ions to achieve the spin alignment(↑↑)(i.e.,facilitating spin polarization),which will strengthen the spin selectivity for accelerating the filtration and transfer of the spins with the same direction for the generation and conversion of triplet ↑O=O↑.Importantly,the origin of magnetic field enhancement on OER/ORR are deeply discussed,which provides a great vision for the magnetism-assisted catalysis.Finally,the challenges and perspectives for future development of spin/magnetism catalysis are presented.This Review is expected to highlight the significance of spin/magnetism theory in breaking the bottleneck of electrocatalysis field and promote the development of high-efficientcy electrocatalysts for practical applications.
