Transition metal-based nanomaterials have emerged as promising electrocatalysts for oxygen evolution reaction(OER).Considerable research efforts have shown that self-reconstruction occurs on these nanomaterials under ...Transition metal-based nanomaterials have emerged as promising electrocatalysts for oxygen evolution reaction(OER).Considerable research efforts have shown that self-reconstruction occurs on these nanomaterials under operating conditions of OER process.However,most of them undergo incomplete reconstruction with limited thickness of reconstruction layer,leading to low component utilization and arduous exploration of real catalytic mechanism.Herein,we identify the dynamic behaviors in complete reconstruction of Co-based complexes during OER.The hollow phytic acid(PA)cross-linked CoFe-based complex nanoboxes with porous nanowalls are designed because of their good electrolyte penetration and mass transport ability,in favor of the fast and complete reconstruction.A series of experiment characterizations demonstrate that the reconstruction process includes the fast substitution of PA by OH-to form Co(Fe)(OH)xand subsequent potential-driven oxidation to Co(Fe)OOH.The obtained CoFeOOH delivers a low overpotential of 290 mV at a current density of 10 mA cm^(-2)and a long-term stability.The experiment results together with theory calculations reveal that the Fe incorporation can result in the electron rearrangement of reconstructed CoFeOOH and optimization of their electronic structure,accounting for the enhanced OER activity.The work provides new insights into complete reconstruction of metal-based complexes during OER and offers guidelines for rational design of high-performance electrocatalysts.展开更多
Synthesis of functional polyethylene from ethylene alone is tricky and heavily dependent on both the type and structure of the precatalyst and the choice of cocatalyst used in the polymerization.In the present study,a...Synthesis of functional polyethylene from ethylene alone is tricky and heavily dependent on both the type and structure of the precatalyst and the choice of cocatalyst used in the polymerization.In the present study,a series of cobalt precatalysts was prepared and investigated for ethylene polymerization under various conditions.By incorporation of strong electron-withdrawing groups(F and NO_(2))and a steric component(benzhydryl)into the parent bis(imino)pyridine ligand,the catalytic performance of these precatalysts was optimized.On activation with MAO or MMAO,these precatalysts with relatively open structure achieved unprecedented ethylene polymerization rates at 60℃(up to 27.6×10^(6)g mol^(−1)h^(−1))and remained effective at temperatures up to 100℃.Chain growth reactions were moderate,resulting in polyethylene with molecular weights up to 61.0 kg/mol and broad bimodal dispersity index.High crystallinity and melt temperature indicated a strictly linear microstructure,as further confirmed by high-temperature^(1)H/^(13)C NMR measurements.Of significant note that chain termination predominantly occurred throughβ-elimination(up to 84.5%),yielding vinyl-terminated long-chain olefins.These functionalα-macro-olefins are valuable as precursors for postfunctionalization,expanding the potential applications of polyethylene across various sectors.展开更多
Palladacycles remain a challenging and significant research field in organic chemistry and have emerged as a type of powerful and versatile precatalysts or key active intermediates for transition metal catalysis.These...Palladacycles remain a challenging and significant research field in organic chemistry and have emerged as a type of powerful and versatile precatalysts or key active intermediates for transition metal catalysis.These achievements in this area are correlated to the design and development of useful ancillary ligands,such as N-heterocyclic carbenes(NHCs),which not only stabilize the actual catalytic active species facilitating the transformations,but also provide additional control over the selectivity of reactions.In this context,NHCs-ligated palladacycles(NHCP_(dcycles))with different electronic and steric properties have been synthesized and applied as green precatalysts(high stability and activity,low catalyst loading and mild reaction conditions)to accelerate transition metalcatalyzed reactions.Therefore,this review focuses mainly on the strategy of NHC-Pd_(cycles) design and catalytic results obtained from representative transition metal catalysis,such as Suzuki-Miyaura,Heck-Mizoroki and Sonogashira cross-coupling reactions,Buchwald-Hartwig amination,carbonylation as well as arylation.At last,the current limitations and potential trends for further development of NHC-Pdcycles are also highlighted.展开更多
The electrocatalytic furfural oxidation reaction(FFOR)represents an economical and promising technology to replace conventional oxygen evolution reaction,enabling the co-production of high value chemicals and H_(2).Re...The electrocatalytic furfural oxidation reaction(FFOR)represents an economical and promising technology to replace conventional oxygen evolution reaction,enabling the co-production of high value chemicals and H_(2).Regulating the adsorption of furfural(FF)and OH^(-)species holds paramount importance in enhancing the overall performance.Herein,we have developed a unique CuO catalyst enriched with oxygen vacancies(O_(v)-CuO)resulting from the electrochemical reconstruction ofα-Cu_(2)S,which demonstrates exceptional FFOR performance,with a conversion of 95.3%,near-perfect selectivity and Faraday efficiency(FE)for furoic acid(FA)at 1.475 V vs.RHE.The study provides detailed comparison of the structural evolution of different sulfide precatalysts and their impact on FFOR.Furthermore,it delves into the structure-activity relationship through a combination of characterization and theoretical calculations.The O_(v)-CuO not only enhances OH^(-)adsorption,changes the rate-determining step,but also reduces the reaction energy barrier toward FFOR.Additionally,a much lower cell voltage is required to coproduce FA and hydrogen in the two-electrode co-electrolysis system.This work would provide valuable insights into the reaction mechanism of FFOR on Cu based catalysts and establish guidelines for designing defective electrocatalysts for biomass conversion.展开更多
A group of five bis(arylimino)pyridine-cobalt(Ⅱ)chloride complexes,[2-{(2,6-(Ph_(2)CH)_(2)-4-MeOC_(6)H_(2))N=CMe}-6-(ArN=CMe)C_5 H_(3)N]CoCl_(2)(Ar=2,6-Me_(2)C_(6)H_(3)Co1,2,6-Et_(2)C_(6)H_(3)Co2,2,6-iPr_(2)C_(6)H_(3...A group of five bis(arylimino)pyridine-cobalt(Ⅱ)chloride complexes,[2-{(2,6-(Ph_(2)CH)_(2)-4-MeOC_(6)H_(2))N=CMe}-6-(ArN=CMe)C_5 H_(3)N]CoCl_(2)(Ar=2,6-Me_(2)C_(6)H_(3)Co1,2,6-Et_(2)C_(6)H_(3)Co2,2,6-iPr_(2)C_(6)H_(3)Co3,2,4,6-Me_(3)C_(6)H_(2)Co4,2,6-Et_(2)-4-MeC_(6)H_(2)Co5),each containing one N-4-methoxy-2,6-dibenzhydrylphenyl group and one smaller sterically/electronically variable N-aryl group,have been synthesized in good yield(>71%)from the corresponding neutral terdentate nitrogen-donor precursor,L1-L5.All complexes have been characterized by^(1)H-NMR and FTIR spectroscopy with the former highlighting the paramagnetic nature of these cobaltous species and the unsymmetrical nature of the chelating ligand.The molecular structures of Co3 and Co4 emphasize the steric differences of the two inequivalent N-aryl groups and the distorted square pyramidal geometry about the metal centers.In the presence of MAO or MMAO,Co1-Co5 collectively displayed high activities for ethylene polymerization producing high molecular weight polyethylenes that,in general,exhibited narrow dispersities(M_w/M_n values:2.12-4.07).Notably,the least sterically hindered Co1 when activated with MAO was the most productive(6.92×10^(6)g_(PE)·mol^(-1)_((Co))·h^(-1))at an operating temperature of60℃.Conversely,the most sterically hindered Co3/MMAO produced the highest molecular weight polyethylene(M_w=6.29×10^(5)g·mol^(-1)).All the polymers displayed high linearity as demonstrated by their melting temperatures(>130℃)and their~1 H-and^(13)C-NMR spectra.By comparison of Co1 with its para-methyl,-chloro and-nitro counterparts,the presence of the para-methoxy substituent showed the most noticeable effect of enhancing the thermal stability of the catalyst.展开更多
基金National Natural Science Foundation of China(22478310,U21A20286 and 22206054)。
文摘Transition metal-based nanomaterials have emerged as promising electrocatalysts for oxygen evolution reaction(OER).Considerable research efforts have shown that self-reconstruction occurs on these nanomaterials under operating conditions of OER process.However,most of them undergo incomplete reconstruction with limited thickness of reconstruction layer,leading to low component utilization and arduous exploration of real catalytic mechanism.Herein,we identify the dynamic behaviors in complete reconstruction of Co-based complexes during OER.The hollow phytic acid(PA)cross-linked CoFe-based complex nanoboxes with porous nanowalls are designed because of their good electrolyte penetration and mass transport ability,in favor of the fast and complete reconstruction.A series of experiment characterizations demonstrate that the reconstruction process includes the fast substitution of PA by OH-to form Co(Fe)(OH)xand subsequent potential-driven oxidation to Co(Fe)OOH.The obtained CoFeOOH delivers a low overpotential of 290 mV at a current density of 10 mA cm^(-2)and a long-term stability.The experiment results together with theory calculations reveal that the Fe incorporation can result in the electron rearrangement of reconstructed CoFeOOH and optimization of their electronic structure,accounting for the enhanced OER activity.The work provides new insights into complete reconstruction of metal-based complexes during OER and offers guidelines for rational design of high-performance electrocatalysts.
基金financially supported by the Chemistry and Chemical Engineering Guangdong Laboratory(2111018 and 2132012)K.F.T.would like to express gratitude towards the ANSO Scholarship Program for their support.
文摘Synthesis of functional polyethylene from ethylene alone is tricky and heavily dependent on both the type and structure of the precatalyst and the choice of cocatalyst used in the polymerization.In the present study,a series of cobalt precatalysts was prepared and investigated for ethylene polymerization under various conditions.By incorporation of strong electron-withdrawing groups(F and NO_(2))and a steric component(benzhydryl)into the parent bis(imino)pyridine ligand,the catalytic performance of these precatalysts was optimized.On activation with MAO or MMAO,these precatalysts with relatively open structure achieved unprecedented ethylene polymerization rates at 60℃(up to 27.6×10^(6)g mol^(−1)h^(−1))and remained effective at temperatures up to 100℃.Chain growth reactions were moderate,resulting in polyethylene with molecular weights up to 61.0 kg/mol and broad bimodal dispersity index.High crystallinity and melt temperature indicated a strictly linear microstructure,as further confirmed by high-temperature^(1)H/^(13)C NMR measurements.Of significant note that chain termination predominantly occurred throughβ-elimination(up to 84.5%),yielding vinyl-terminated long-chain olefins.These functionalα-macro-olefins are valuable as precursors for postfunctionalization,expanding the potential applications of polyethylene across various sectors.
基金Financial support from the National Natural Science Foundation of China(No.22101133)the Natural Science Foundation of Jiangsu Province(No.BK20200768)is greatly acknowledged.
文摘Palladacycles remain a challenging and significant research field in organic chemistry and have emerged as a type of powerful and versatile precatalysts or key active intermediates for transition metal catalysis.These achievements in this area are correlated to the design and development of useful ancillary ligands,such as N-heterocyclic carbenes(NHCs),which not only stabilize the actual catalytic active species facilitating the transformations,but also provide additional control over the selectivity of reactions.In this context,NHCs-ligated palladacycles(NHCP_(dcycles))with different electronic and steric properties have been synthesized and applied as green precatalysts(high stability and activity,low catalyst loading and mild reaction conditions)to accelerate transition metalcatalyzed reactions.Therefore,this review focuses mainly on the strategy of NHC-Pd_(cycles) design and catalytic results obtained from representative transition metal catalysis,such as Suzuki-Miyaura,Heck-Mizoroki and Sonogashira cross-coupling reactions,Buchwald-Hartwig amination,carbonylation as well as arylation.At last,the current limitations and potential trends for further development of NHC-Pdcycles are also highlighted.
基金supported by the Natural Science Foundation of Zhejiang Province(ZCLZ24B0301)the Lhasa Central Government Guiding Local Science and Technology Development Funds(No.LSKJ202458)the National Natural Science Foundation of China(No.22472150)。
文摘The electrocatalytic furfural oxidation reaction(FFOR)represents an economical and promising technology to replace conventional oxygen evolution reaction,enabling the co-production of high value chemicals and H_(2).Regulating the adsorption of furfural(FF)and OH^(-)species holds paramount importance in enhancing the overall performance.Herein,we have developed a unique CuO catalyst enriched with oxygen vacancies(O_(v)-CuO)resulting from the electrochemical reconstruction ofα-Cu_(2)S,which demonstrates exceptional FFOR performance,with a conversion of 95.3%,near-perfect selectivity and Faraday efficiency(FE)for furoic acid(FA)at 1.475 V vs.RHE.The study provides detailed comparison of the structural evolution of different sulfide precatalysts and their impact on FFOR.Furthermore,it delves into the structure-activity relationship through a combination of characterization and theoretical calculations.The O_(v)-CuO not only enhances OH^(-)adsorption,changes the rate-determining step,but also reduces the reaction energy barrier toward FFOR.Additionally,a much lower cell voltage is required to coproduce FA and hydrogen in the two-electrode co-electrolysis system.This work would provide valuable insights into the reaction mechanism of FFOR on Cu based catalysts and establish guidelines for designing defective electrocatalysts for biomass conversion.
基金financially supported by the National Natural Science Foundation of China(No.21871275)。
文摘A group of five bis(arylimino)pyridine-cobalt(Ⅱ)chloride complexes,[2-{(2,6-(Ph_(2)CH)_(2)-4-MeOC_(6)H_(2))N=CMe}-6-(ArN=CMe)C_5 H_(3)N]CoCl_(2)(Ar=2,6-Me_(2)C_(6)H_(3)Co1,2,6-Et_(2)C_(6)H_(3)Co2,2,6-iPr_(2)C_(6)H_(3)Co3,2,4,6-Me_(3)C_(6)H_(2)Co4,2,6-Et_(2)-4-MeC_(6)H_(2)Co5),each containing one N-4-methoxy-2,6-dibenzhydrylphenyl group and one smaller sterically/electronically variable N-aryl group,have been synthesized in good yield(>71%)from the corresponding neutral terdentate nitrogen-donor precursor,L1-L5.All complexes have been characterized by^(1)H-NMR and FTIR spectroscopy with the former highlighting the paramagnetic nature of these cobaltous species and the unsymmetrical nature of the chelating ligand.The molecular structures of Co3 and Co4 emphasize the steric differences of the two inequivalent N-aryl groups and the distorted square pyramidal geometry about the metal centers.In the presence of MAO or MMAO,Co1-Co5 collectively displayed high activities for ethylene polymerization producing high molecular weight polyethylenes that,in general,exhibited narrow dispersities(M_w/M_n values:2.12-4.07).Notably,the least sterically hindered Co1 when activated with MAO was the most productive(6.92×10^(6)g_(PE)·mol^(-1)_((Co))·h^(-1))at an operating temperature of60℃.Conversely,the most sterically hindered Co3/MMAO produced the highest molecular weight polyethylene(M_w=6.29×10^(5)g·mol^(-1)).All the polymers displayed high linearity as demonstrated by their melting temperatures(>130℃)and their~1 H-and^(13)C-NMR spectra.By comparison of Co1 with its para-methyl,-chloro and-nitro counterparts,the presence of the para-methoxy substituent showed the most noticeable effect of enhancing the thermal stability of the catalyst.
