Ln-containing polyoxoniobates(PONbs)have appealing applications in luminescence,information encryption and magnetic fields,but the synthesis of PONbs containing high-nuclearity Ln-O clusters is challenging due to the ...Ln-containing polyoxoniobates(PONbs)have appealing applications in luminescence,information encryption and magnetic fields,but the synthesis of PONbs containing high-nuclearity Ln-O clusters is challenging due to the easy hydrolysis of Ln^(3+)ions in alkaline environments.In this paper,we are able to integrate CO_(3)^(2-)and high-nuclearity Ln-O clusters into PONb to construct an inorganic giant Eu_(19)-embedded PONb H_(49)K_(16)Na_(13)(H_(2)O)_(63)[Eu_(21)O_(2)(OH)_(7)(H_(2)O)_(5)(Nb_(7)O_(22))_(10)(Nb_(2)O_(6))_(2)(CO_(3))_(18)]·91H_(2)O(1),which contains the highest nuclearity Eu-O clusters and the largest number of Eu^(3+)ions among PONbs.In addition,the film that was prepared by mixing 1 with gelatin and glycerol,exhibits reversible luminescence switching behavior under acid/alkali stimulation and has been used to create a fluorescence-encoded information approach.This work paves a feasible strategy for the construction of high-nuclearity Ln-O cluster-containing PONbs and the expansion of the application of Ln-containing PONbs in information encryption.展开更多
The development of core-shell nanoclusters with controllable composition is of utmost importance as the material properties depend on their constituent elements.However,precisely tuning their compositions at the atomi...The development of core-shell nanoclusters with controllable composition is of utmost importance as the material properties depend on their constituent elements.However,precisely tuning their compositions at the atomic scale is not easily achieved because of the difficulty of using limited macroscopic synthetic methods for atomic-level modulation.In this work,we report an interesting example of precisely regulating the core composition of an inorganic core-shell-type cobalt polyoxoniobate[Co_(26)Nb_(36)O_(140)]^(32−)by controlling reaction conditions,in which the inner Co-core composition could be tune while retaining the outer Nb-shell composition of resulting product,leading to a series of isostructural species with a general formula of{Co_(26-n)Nb_(36+n)O_(140)}(n=0–2).These rare species not only can display good powder and single-crystal proton conductivities,but also might provide helpful and atomic-level insights into the syntheses,structures and composition modifications of inorganic amorphous core-shell heterometal oxide nanoparticles.展开更多
A family of rare-earth derivant mixed-polyoxoniobate clusters K_(12)(NH_(4))10[{Nb_(12)P_(4)W_(24)O_(122)}_(2){Ln(H_(2)O)_(5)}_(4){Nb_(4)O_(4)(OH)_(6)}]·xH_(2)O(Ln=Sm,Eu,Tb,Dy,Er,Tm and Yb for 1–7,abbreviated as...A family of rare-earth derivant mixed-polyoxoniobate clusters K_(12)(NH_(4))10[{Nb_(12)P_(4)W_(24)O_(122)}_(2){Ln(H_(2)O)_(5)}_(4){Nb_(4)O_(4)(OH)_(6)}]·xH_(2)O(Ln=Sm,Eu,Tb,Dy,Er,Tm and Yb for 1–7,abbreviated as{Ln_(4)Nb_(28)})were synthesized and structurally characterized by single-crystal X-ray diffraction,elemental analyses,IR spectroscopy and TG analyses.Containing four Wells–Dawson[Nb_(6)P_(2)W_(12)O_(62)]^(12)−,a{Nb_(4)O_(6)}core,and four Ln^(Ⅲ) ions,the polyanions in 1–7 are a group of rare-earth derivants of phosphoniobotungstates.These water-soluble clusters behave as weak acids with good stability and high proton release capacity depending on the pH.Each cluster carries~22 negative charges in the aqueous solution without any deprotonation with the pH the same as that used for deionized water.Upon the introduction of bases,they get deprotonated gradually and each anion cluster can release up to 20 protons from its 20 coordinated water ligands.The pKa values of these acidic clusters with different degrees of deprotonation range from~8.3 to~10.5.Moreover,these clusters demonstrate an increasing deprotonation efficiency with the decreasing ionic radius of incorporated Ln^(Ⅲ) ions,which could be attributed to the lanthanide contraction.In other words,the{Ln_(4)Nb_(28)}macroanion clusters with smaller Ln^(Ⅲ) centers are easier to deprotonate due to their shorter and stronger Ln–O bonds.This is the first study that focuses on the effect of lanthanide contraction on proton release in polyoxometalate chemistry.The{Ln_(4)Nb_(28)}clusters with good stability,high proton release capacity,and controllable deprotonation efficiency provide models for the understanding of protonated polyelectrolyte solutions,and the design and applications of polyoxometalatebased protonated materials.展开更多
The gram-scale preparation of efficient polyoxometalate catalysts is an everlasting yet challenging goal for sustainable organic conversion processes.Herein we report a facile ball-milling strategy to prepare polyoxon...The gram-scale preparation of efficient polyoxometalate catalysts is an everlasting yet challenging goal for sustainable organic conversion processes.Herein we report a facile ball-milling strategy to prepare polyoxoniobate-intercalated layered double hydroxide(Mg_(3)Al-LDH-Nb_(6))that shows quite high catalytic activity for the Aldol and Michael addition cascade reactions,e.g.selective synthesis of polysubstituted cyclohexanols and 1,5-diones from arylaldehydes and arylketones.The gram-scale preparation and high reusability with negligible loss of catalytic activity of the Mg_(3)Al-LDH-Nb_(6) catalyst would greatly promote its industrial applications.Additionally,some catalysts exhibit good inhibition effects against human cervix tumor cells(HeLa)and lung cancer human alveolar basal epithelial cells(A549).This work not only develops a facile method for the gram-scale preparation of a new polyoxoniobate-intercalated layered double hydroxide catalyst but also highlights promising biological applications of the catalytic products.展开更多
The overall energy efficiency of electrochemical systems is significantly reduced by the conventional anodic oxygen evolution reaction(OER).It is feasible to improve energy efficiency by replacing the OER with the ure...The overall energy efficiency of electrochemical systems is significantly reduced by the conventional anodic oxygen evolution reaction(OER).It is feasible to improve energy efficiency by replacing the OER with the urea oxidation reaction(UOR),which has a lower thermodynamic potential.An organic–inorganic hybrid polyoxoniobate decorated by a Co(Ⅲ)-amine complex,Na_(4)(H_(2)O)_(15)[Co(en)_(3)]_(2){[Co(en)(Nb_(6)O_(19))]_(2)}·34H_(2)O(Co_(2)Nb_(6),en=ethylenediamine)with distinct physicochemical characteristics and well-defined single-crystal structure is reported.The structure of Co_(2)Nb_(6)contains Lindqvist{[Co(en)(Nb_(6)O_(19))]_(2)}^(10−)dimer and free[Co(en)_(3)]^(3+)complexes.Co_(2)Nb_(6)exhibits remarkable catalytic activity for the UOR after being firmly attached to the surface of acetylene black by polyethyleneimine(PEI).To the best of our knowledge,this is the first instance of performing the electrocatalytic UOR based on Lindqvist polyoxoniobate clusters,which will pave the path for innovative concepts in the development of POMbased electrocatalysts.展开更多
The search for polyoxometalate-based catalysts has long attracted interest.Being designable in structure,stable and effective,polyoxoniobate-based catalysts have an exciting prospect for industrial applications.This p...The search for polyoxometalate-based catalysts has long attracted interest.Being designable in structure,stable and effective,polyoxoniobate-based catalysts have an exciting prospect for industrial applications.This paper not only summarizes recent advances in classic polyoxoniobate-catalyzed reactions,including chemical warfare agents and organic dyes degradation,epoxidation reactions,photocatalytic hydrogen evolution and base-catalyzed reactions but also discusses some representative cases and the speculative mechanism related to structures.In addition,the current challenges and perspectives in the fabrication of more efficient and promising polyoxoniobate-based catalysts are also presented.展开更多
A rare 3D porous chiral polyoxoniobate framework,[Cu(en)_(2)(H_(2)O)]_(2){[Cu(en)]_(4)[Cu(en)_(2)]_(5){[Cu(en)_(2)KNb_(24)O_(72)H_(10)]_(2)}·6en·70H_(2O)(1)(en=ethylenediamine)based on two types of isomeric{...A rare 3D porous chiral polyoxoniobate framework,[Cu(en)_(2)(H_(2)O)]_(2){[Cu(en)]_(4)[Cu(en)_(2)]_(5){[Cu(en)_(2)KNb_(24)O_(72)H_(10)]_(2)}·6en·70H_(2O)(1)(en=ethylenediamine)based on two types of isomeric{Cu(en)_(2)KNb_(24)O_(72)H10}clusters(α-CuKNb_(24)andβ-CuKNb_(24))has been synthesized by a hydrothermal reaction.Interestingly,theα-CuKNb_(24)andβ-CuKNb_(24)clusters are connected by cupric complexes to form chiral helical pillars with left-handedness(L-α-CuKNb_(24))and right-handedness(R-β-CuKNb_(24)).To our knowl edge,compound 1 is thefirst polyoxometalate-based MOF with a 4-connected neb-type topology struc ture within polyoxometalate chemistry.This compound also exhibits proton conduction and strong water vapor adsorption properties.展开更多
Polyoxoniobates(PONbs)and polyoxotantalates(POTas)are anionic metal–oxide clusters composed of Nb^(V) and Ta^(V),which have higher charge–size ratios than polyoxotungstates and polyoxomolybdates.The synthesis of PON...Polyoxoniobates(PONbs)and polyoxotantalates(POTas)are anionic metal–oxide clusters composed of Nb^(V) and Ta^(V),which have higher charge–size ratios than polyoxotungstates and polyoxomolybdates.The synthesis of PONbs and POTas usually involves the use of [X_(6)O_(19)]^(8−)(X=Nb,Ta)as precursors,which confine the pH of aqueous solutions to be consistently confined to the alkaline region of the pH scale,rendering them incompatible with the reactivity of most metal cations.Due to the lack of negative analogues to MO_(4)^(2−)(M=Mo/W)that can be polymerized through acidification,the progress in the study of [X_(6)O_(19)]^(8−)(X=Nb,Ta)polyanions under acidic conditions remains in its nascent stages.The methods reported to date for synthesizing PONb and POTa clusters can be categorized into two broad strategies:ligand protection under alkaline conditions and hydrogen peroxide(H_(2)O_(2))utilization under acidic conditions.In the latter strategy,H_(2)O_(2) is used to prevent the formation of Nb_(2)O_(5) or Ta_(2)O_(5) in an acidic solution by grafting peroxo groups onto the Nb or Ta atoms.The subsequent cleavage of the peroxo O–O bond enhances the reactivity of oxo intermediates,facilitating the prediction and rational design of novel reactions.In this review,we provide an overview of recent developments from the recent studies on the reaction of [X_(6)O_(19)]^(8−)(X=Nb,Ta)polyanions under acidic conditions,spanning from the synthesis to the structural elucidation of PONb and POTa clusters.These developments fall into two main categories:mixed-addendum niobotungstates/tantalotungstates and hetero-peroxo-PONb/Ta clusters.Furthermore,we briefly introduce the properties and applications of some compounds.The concluding section is dedicated to discussing the prospects and essential guidance in this field.展开更多
The N-formylation of amines with CO_(2)and hydrosilanes is an emerging yet important reaction in fine chemical industry.Herein,we have reported a methyltrioctylammonium cation(TOMA)stabilized Nb oxocluster catalyst th...The N-formylation of amines with CO_(2)and hydrosilanes is an emerging yet important reaction in fine chemical industry.Herein,we have reported a methyltrioctylammonium cation(TOMA)stabilized Nb oxocluster catalyst that can effectively realize two electron reduction of CO_(2)and form C-N bond simultaneously,leading to the corresponding formamides.The oxocluster catalyst exhibits excellent catalytic activity to transform secondary and primary amines into the corresponding formamides,with the conversion ranging from 81.5%to 99.2%under room temperature conditions.Furthermore,the Nb oxocluster catalyst shows the unique characteristics of ionic liquids,and it is highly robust and easy to be recycled for five times with negligible loss of catalytic activity.On the basis of the activity tests and structure characterization of Nb catalysts,it was found that TOMA cation played an important role in modulating the Nb oxocluster with high stability and uniform dispersion.The mechanism studies demonstrate that the formylation reaction proceeds through the formation of silyl formate intermediate rather than carbamate,and the Lewis base site of negative oxygen atoms from polyoxoniobate anions can exert a favorable impact on activation both CO_(2)and Si-H bond of PhSiH 3,allowing that N-formylation reaction proceed smoothly under very mild reaction conditions.展开更多
基金the financial support from the National Natural Science Foundation of China(Nos.21971040,22171045,and 22371046)。
文摘Ln-containing polyoxoniobates(PONbs)have appealing applications in luminescence,information encryption and magnetic fields,but the synthesis of PONbs containing high-nuclearity Ln-O clusters is challenging due to the easy hydrolysis of Ln^(3+)ions in alkaline environments.In this paper,we are able to integrate CO_(3)^(2-)and high-nuclearity Ln-O clusters into PONb to construct an inorganic giant Eu_(19)-embedded PONb H_(49)K_(16)Na_(13)(H_(2)O)_(63)[Eu_(21)O_(2)(OH)_(7)(H_(2)O)_(5)(Nb_(7)O_(22))_(10)(Nb_(2)O_(6))_(2)(CO_(3))_(18)]·91H_(2)O(1),which contains the highest nuclearity Eu-O clusters and the largest number of Eu^(3+)ions among PONbs.In addition,the film that was prepared by mixing 1 with gelatin and glycerol,exhibits reversible luminescence switching behavior under acid/alkali stimulation and has been used to create a fluorescence-encoded information approach.This work paves a feasible strategy for the construction of high-nuclearity Ln-O cluster-containing PONbs and the expansion of the application of Ln-containing PONbs in information encryption.
基金the financial support from the National Natural Science Foundation of China(Nos.21971039 and 22171045)and the Key Program of Natural Science Foundation of Fujian Province(No.2021J02007).
文摘The development of core-shell nanoclusters with controllable composition is of utmost importance as the material properties depend on their constituent elements.However,precisely tuning their compositions at the atomic scale is not easily achieved because of the difficulty of using limited macroscopic synthetic methods for atomic-level modulation.In this work,we report an interesting example of precisely regulating the core composition of an inorganic core-shell-type cobalt polyoxoniobate[Co_(26)Nb_(36)O_(140)]^(32−)by controlling reaction conditions,in which the inner Co-core composition could be tune while retaining the outer Nb-shell composition of resulting product,leading to a series of isostructural species with a general formula of{Co_(26-n)Nb_(36+n)O_(140)}(n=0–2).These rare species not only can display good powder and single-crystal proton conductivities,but also might provide helpful and atomic-level insights into the syntheses,structures and composition modifications of inorganic amorphous core-shell heterometal oxide nanoparticles.
基金supported by the National Natural Science Foundation of China(21671056 and 22071045)the Excellent Youth Science Fund Project of Henan Province(202300410042)+2 种基金Henan Universitysupport from the National Science Foundation(CHE2132178)The University of Akron.
文摘A family of rare-earth derivant mixed-polyoxoniobate clusters K_(12)(NH_(4))10[{Nb_(12)P_(4)W_(24)O_(122)}_(2){Ln(H_(2)O)_(5)}_(4){Nb_(4)O_(4)(OH)_(6)}]·xH_(2)O(Ln=Sm,Eu,Tb,Dy,Er,Tm and Yb for 1–7,abbreviated as{Ln_(4)Nb_(28)})were synthesized and structurally characterized by single-crystal X-ray diffraction,elemental analyses,IR spectroscopy and TG analyses.Containing four Wells–Dawson[Nb_(6)P_(2)W_(12)O_(62)]^(12)−,a{Nb_(4)O_(6)}core,and four Ln^(Ⅲ) ions,the polyanions in 1–7 are a group of rare-earth derivants of phosphoniobotungstates.These water-soluble clusters behave as weak acids with good stability and high proton release capacity depending on the pH.Each cluster carries~22 negative charges in the aqueous solution without any deprotonation with the pH the same as that used for deionized water.Upon the introduction of bases,they get deprotonated gradually and each anion cluster can release up to 20 protons from its 20 coordinated water ligands.The pKa values of these acidic clusters with different degrees of deprotonation range from~8.3 to~10.5.Moreover,these clusters demonstrate an increasing deprotonation efficiency with the decreasing ionic radius of incorporated Ln^(Ⅲ) ions,which could be attributed to the lanthanide contraction.In other words,the{Ln_(4)Nb_(28)}macroanion clusters with smaller Ln^(Ⅲ) centers are easier to deprotonate due to their shorter and stronger Ln–O bonds.This is the first study that focuses on the effect of lanthanide contraction on proton release in polyoxometalate chemistry.The{Ln_(4)Nb_(28)}clusters with good stability,high proton release capacity,and controllable deprotonation efficiency provide models for the understanding of protonated polyelectrolyte solutions,and the design and applications of polyoxometalatebased protonated materials.
基金financially supported by the National Natural Science Foundation of China(nos 21871125,22171139,21801145 and 21901122)the Natural Science Foundation of Shandong Province,China(nos ZR2019MB043 and ZR2019QB022)+1 种基金the Shandong Provincial Key R&D Program/Major Science and Technology Innovation Project of Shandong Province(2019JZZY020230)the Construction Project of Quality Curriculum for Postgraduate Education of Shandong Province(no.SDYKC19057).
文摘The gram-scale preparation of efficient polyoxometalate catalysts is an everlasting yet challenging goal for sustainable organic conversion processes.Herein we report a facile ball-milling strategy to prepare polyoxoniobate-intercalated layered double hydroxide(Mg_(3)Al-LDH-Nb_(6))that shows quite high catalytic activity for the Aldol and Michael addition cascade reactions,e.g.selective synthesis of polysubstituted cyclohexanols and 1,5-diones from arylaldehydes and arylketones.The gram-scale preparation and high reusability with negligible loss of catalytic activity of the Mg_(3)Al-LDH-Nb_(6) catalyst would greatly promote its industrial applications.Additionally,some catalysts exhibit good inhibition effects against human cervix tumor cells(HeLa)and lung cancer human alveolar basal epithelial cells(A549).This work not only develops a facile method for the gram-scale preparation of a new polyoxoniobate-intercalated layered double hydroxide catalyst but also highlights promising biological applications of the catalytic products.
基金the National Natural Science Foundations of China(No.21971040,21971039 and 21773029).
文摘The overall energy efficiency of electrochemical systems is significantly reduced by the conventional anodic oxygen evolution reaction(OER).It is feasible to improve energy efficiency by replacing the OER with the urea oxidation reaction(UOR),which has a lower thermodynamic potential.An organic–inorganic hybrid polyoxoniobate decorated by a Co(Ⅲ)-amine complex,Na_(4)(H_(2)O)_(15)[Co(en)_(3)]_(2){[Co(en)(Nb_(6)O_(19))]_(2)}·34H_(2)O(Co_(2)Nb_(6),en=ethylenediamine)with distinct physicochemical characteristics and well-defined single-crystal structure is reported.The structure of Co_(2)Nb_(6)contains Lindqvist{[Co(en)(Nb_(6)O_(19))]_(2)}^(10−)dimer and free[Co(en)_(3)]^(3+)complexes.Co_(2)Nb_(6)exhibits remarkable catalytic activity for the UOR after being firmly attached to the surface of acetylene black by polyethyleneimine(PEI).To the best of our knowledge,this is the first instance of performing the electrocatalytic UOR based on Lindqvist polyoxoniobate clusters,which will pave the path for innovative concepts in the development of POMbased electrocatalysts.
基金financially supported by the National Natural Science Foundations of China (Grant Nos. 22171045, 21773029 and 21971039)the Natural Science Fund of Fujian Province (Grant No. 2017J01579)Projects from State Key Laboratory of Structural Chemistry of China
文摘The search for polyoxometalate-based catalysts has long attracted interest.Being designable in structure,stable and effective,polyoxoniobate-based catalysts have an exciting prospect for industrial applications.This paper not only summarizes recent advances in classic polyoxoniobate-catalyzed reactions,including chemical warfare agents and organic dyes degradation,epoxidation reactions,photocatalytic hydrogen evolution and base-catalyzed reactions but also discusses some representative cases and the speculative mechanism related to structures.In addition,the current challenges and perspectives in the fabrication of more efficient and promising polyoxoniobate-based catalysts are also presented.
基金support from the National Natural Science Foundation of China(No.21971039,21971040 and 21773029)the Natural Science Fund of Fujian Province(No.2017J01579).
文摘A rare 3D porous chiral polyoxoniobate framework,[Cu(en)_(2)(H_(2)O)]_(2){[Cu(en)]_(4)[Cu(en)_(2)]_(5){[Cu(en)_(2)KNb_(24)O_(72)H_(10)]_(2)}·6en·70H_(2O)(1)(en=ethylenediamine)based on two types of isomeric{Cu(en)_(2)KNb_(24)O_(72)H10}clusters(α-CuKNb_(24)andβ-CuKNb_(24))has been synthesized by a hydrothermal reaction.Interestingly,theα-CuKNb_(24)andβ-CuKNb_(24)clusters are connected by cupric complexes to form chiral helical pillars with left-handedness(L-α-CuKNb_(24))and right-handedness(R-β-CuKNb_(24)).To our knowl edge,compound 1 is thefirst polyoxometalate-based MOF with a 4-connected neb-type topology struc ture within polyoxometalate chemistry.This compound also exhibits proton conduction and strong water vapor adsorption properties.
基金supported by the National Natural Science Foundation of China(22071045)the Excellent Youth Science Fund Project of Henan Province(202300410042)+1 种基金the Natural Science Foundation of Henan Province(232300420372)Henan University.
文摘Polyoxoniobates(PONbs)and polyoxotantalates(POTas)are anionic metal–oxide clusters composed of Nb^(V) and Ta^(V),which have higher charge–size ratios than polyoxotungstates and polyoxomolybdates.The synthesis of PONbs and POTas usually involves the use of [X_(6)O_(19)]^(8−)(X=Nb,Ta)as precursors,which confine the pH of aqueous solutions to be consistently confined to the alkaline region of the pH scale,rendering them incompatible with the reactivity of most metal cations.Due to the lack of negative analogues to MO_(4)^(2−)(M=Mo/W)that can be polymerized through acidification,the progress in the study of [X_(6)O_(19)]^(8−)(X=Nb,Ta)polyanions under acidic conditions remains in its nascent stages.The methods reported to date for synthesizing PONb and POTa clusters can be categorized into two broad strategies:ligand protection under alkaline conditions and hydrogen peroxide(H_(2)O_(2))utilization under acidic conditions.In the latter strategy,H_(2)O_(2) is used to prevent the formation of Nb_(2)O_(5) or Ta_(2)O_(5) in an acidic solution by grafting peroxo groups onto the Nb or Ta atoms.The subsequent cleavage of the peroxo O–O bond enhances the reactivity of oxo intermediates,facilitating the prediction and rational design of novel reactions.In this review,we provide an overview of recent developments from the recent studies on the reaction of [X_(6)O_(19)]^(8−)(X=Nb,Ta)polyanions under acidic conditions,spanning from the synthesis to the structural elucidation of PONb and POTa clusters.These developments fall into two main categories:mixed-addendum niobotungstates/tantalotungstates and hetero-peroxo-PONb/Ta clusters.Furthermore,we briefly introduce the properties and applications of some compounds.The concluding section is dedicated to discussing the prospects and essential guidance in this field.
基金The authors are grateful for financial support from the National Natural Science Foundation of China(21773061,21978095).
文摘The N-formylation of amines with CO_(2)and hydrosilanes is an emerging yet important reaction in fine chemical industry.Herein,we have reported a methyltrioctylammonium cation(TOMA)stabilized Nb oxocluster catalyst that can effectively realize two electron reduction of CO_(2)and form C-N bond simultaneously,leading to the corresponding formamides.The oxocluster catalyst exhibits excellent catalytic activity to transform secondary and primary amines into the corresponding formamides,with the conversion ranging from 81.5%to 99.2%under room temperature conditions.Furthermore,the Nb oxocluster catalyst shows the unique characteristics of ionic liquids,and it is highly robust and easy to be recycled for five times with negligible loss of catalytic activity.On the basis of the activity tests and structure characterization of Nb catalysts,it was found that TOMA cation played an important role in modulating the Nb oxocluster with high stability and uniform dispersion.The mechanism studies demonstrate that the formylation reaction proceeds through the formation of silyl formate intermediate rather than carbamate,and the Lewis base site of negative oxygen atoms from polyoxoniobate anions can exert a favorable impact on activation both CO_(2)and Si-H bond of PhSiH 3,allowing that N-formylation reaction proceed smoothly under very mild reaction conditions.
