Binuclear ruthenium complexes bearing the2,2'‐bipyridine‐6,6'‐dicarboxylate(bda)ligand have been demonstrated to be highly active catalysts towards water oxidation with CeIV as an oxidant.However,the cataly...Binuclear ruthenium complexes bearing the2,2'‐bipyridine‐6,6'‐dicarboxylate(bda)ligand have been demonstrated to be highly active catalysts towards water oxidation with CeIV as an oxidant.However,the catalytic properties of ruthenium dimers have not yet been explored for visible light‐driven water oxidation.Herein,the photocatalytic performance of a dipyridyl propane‐bridged ruthenium dimer2was investigated in comparison with its monomeric precursor,[Ru(bda)(pic)2](1),in CH3CN/phosphate buffer mixed solvent in a three‐component system including a photosensitizer and a sacrificial electron acceptor.Experimental results showed that the activity of each catalyst was strongly dependent on the content of CH3CN in the phosphate buffer,which not only affected the driving force for water oxidation,but also altered the kinetics of the reaction,probably through different mechanisms associated with the O–O bond formation.As a result,dimer2showedsignificantly higher activity than monomer1in the solvent containing a low content of CH3CN,and comparable activities were attained with a high content of CH3CN in the solvent.Under the optimal conditions,complex2achieved a turnover number of638for photocatalytic O2evolution.展开更多
Polyolefins are globally important plastics.Molecular weight and molecular weight distribution are two key parameters for determining the properties of polyolefin materials.In this contribution,we develop a strategy f...Polyolefins are globally important plastics.Molecular weight and molecular weight distribution are two key parameters for determining the properties of polyolefin materials.In this contribution,we develop a strategy for combining the macrocyclic framework and the binuclear effect into the benchmarkα-diimine late transition metal catalysts,and thus macrocyclic binuclearα-diimine nickel catalysts(Ni_(2)-Me and Ni_(2)-iPr)are prepared.Compared to the classical Brookhart's acyclic mononuclearα-diimine nickel analogues(Ni_(1)-Me and Ni_(1)-iPr),these nickel catalysts exhibit enhanced thermostability(up to 110℃)and produce polyethylenes with higher molecular weights(up to 7 times)and lower branching densities(as low as 9 branches/1000C)in methylaluminoxane(MAO)activated ethylene polymerization.This translates into the ability of the catalyst to afford more linear high molecular weight polyethylenes.In particular,bimodal polyethylenes with broad molecular weight distributions(Mw/Mn=8.08-14.66)are generated by the sole catalyst.This work affords diverse polyethylenes.展开更多
使用桥连配体锂盐与MCl4络合,合成了4个不同结构的双核茂金属化合物[μ,μ-(CH2)3]{[C(H)·(η5-C5H4)(η^5-C13H8)](MCl2)}2[M=Zr or Ti](4,5)和[μ,μ-(CH2)3]{[C(H)(η^5-C5H4)(η^5-C9H6)]·(MCl2)}2[M=Zr or Ti](6,7),配...使用桥连配体锂盐与MCl4络合,合成了4个不同结构的双核茂金属化合物[μ,μ-(CH2)3]{[C(H)·(η5-C5H4)(η^5-C13H8)](MCl2)}2[M=Zr or Ti](4,5)和[μ,μ-(CH2)3]{[C(H)(η^5-C5H4)(η^5-C9H6)]·(MCl2)}2[M=Zr or Ti](6,7),配体和化合物都经过核磁氢谱(1HNMR)、碳谱(13CNMR)、红外光谱(IR)及元素分析等表征,确认了化学结构.以甲基铝氧烷(MAO)为助催化剂,化合物4~7为催化剂催化丙烯聚合,考察了聚合温度、乙烯压力、铝钛或铝锆比对催化剂活性及聚合物分子量的影响.结果表明,多亚甲基桥连双核茂金属是高活性乙烯和丙烯聚合催化剂,乙烯聚合活性最高达到7.5×10^6gPE/(molZr·h)(化合物6),丙烯聚合活性达10×10^5gsPP/(molZr·h)(化合物4).所得间规聚丙烯(sPP)的间规度指数(SI,r)达到90%.在同样条件下,双核化合物的催化活性、聚合物分子量Mw(>100000)以及分子量分布(MWD>2.5)均比相应的单核化合物高(Mw<70000,MWD≤2),表明该体系中存在较强的核效应.展开更多
Binuclear iron phthalocyanine/reduced graphene oxide(bi-Fe Pc/RGO) nanocomposite with good electrocatalytic activity for ORR in alkaline medium was prepared in one step. High angle annular dark field image scanning tr...Binuclear iron phthalocyanine/reduced graphene oxide(bi-Fe Pc/RGO) nanocomposite with good electrocatalytic activity for ORR in alkaline medium was prepared in one step. High angle annular dark field image scanning transmission electron microscopy(HAADF-STEM) and energy dispersive X-ray spectroscopy element mapping results show bi-Fe Pc was uniformly distributed on RGO. An obvious cathodic peak located at about-0.23 V(vs. SCE) in CV and an onset potential of-0.004 V(vs. SCE) in LSV indicate the as-prepared bi-Fe Pc/RGO nanocomposite possesses high activity which is closed to Pt/C for ORR. The ORR on bi-Fe Pc/RGO nanocomposite follows four-electron transfer pathway in alkaline medium. Compared with Pt/C, there is only a slight decrease(about 0.02 V vs. SCE) for bi-Fe Pc/RGO nanocomposite when the methanol exists. The excellent activity and methanol tolerance in alkaline solutions proves that bi-Fe Pc/RGO nanocomposite could be considered as a promising cathode catalyst for alkaline fuel cells.展开更多
基金supported by the National Basic Research Program of China (973 Program, 2014CB239402)the National Natural Science Foundation of China (21476043)+1 种基金the Fundamental Research Funds for the Central Universities (DUT17ZD204)the Swedish Energy Agency and K&A Wallenberg Foundation~~
文摘Binuclear ruthenium complexes bearing the2,2'‐bipyridine‐6,6'‐dicarboxylate(bda)ligand have been demonstrated to be highly active catalysts towards water oxidation with CeIV as an oxidant.However,the catalytic properties of ruthenium dimers have not yet been explored for visible light‐driven water oxidation.Herein,the photocatalytic performance of a dipyridyl propane‐bridged ruthenium dimer2was investigated in comparison with its monomeric precursor,[Ru(bda)(pic)2](1),in CH3CN/phosphate buffer mixed solvent in a three‐component system including a photosensitizer and a sacrificial electron acceptor.Experimental results showed that the activity of each catalyst was strongly dependent on the content of CH3CN in the phosphate buffer,which not only affected the driving force for water oxidation,but also altered the kinetics of the reaction,probably through different mechanisms associated with the O–O bond formation.As a result,dimer2showedsignificantly higher activity than monomer1in the solvent containing a low content of CH3CN,and comparable activities were attained with a high content of CH3CN in the solvent.Under the optimal conditions,complex2achieved a turnover number of638for photocatalytic O2evolution.
基金This work was supported by the National Natural Science Foundation of China(No.22122110)the Science and Technology Department Program of Jilin Province,China(No.20230101347JC).
文摘Polyolefins are globally important plastics.Molecular weight and molecular weight distribution are two key parameters for determining the properties of polyolefin materials.In this contribution,we develop a strategy for combining the macrocyclic framework and the binuclear effect into the benchmarkα-diimine late transition metal catalysts,and thus macrocyclic binuclearα-diimine nickel catalysts(Ni_(2)-Me and Ni_(2)-iPr)are prepared.Compared to the classical Brookhart's acyclic mononuclearα-diimine nickel analogues(Ni_(1)-Me and Ni_(1)-iPr),these nickel catalysts exhibit enhanced thermostability(up to 110℃)and produce polyethylenes with higher molecular weights(up to 7 times)and lower branching densities(as low as 9 branches/1000C)in methylaluminoxane(MAO)activated ethylene polymerization.This translates into the ability of the catalyst to afford more linear high molecular weight polyethylenes.In particular,bimodal polyethylenes with broad molecular weight distributions(Mw/Mn=8.08-14.66)are generated by the sole catalyst.This work affords diverse polyethylenes.
文摘使用桥连配体锂盐与MCl4络合,合成了4个不同结构的双核茂金属化合物[μ,μ-(CH2)3]{[C(H)·(η5-C5H4)(η^5-C13H8)](MCl2)}2[M=Zr or Ti](4,5)和[μ,μ-(CH2)3]{[C(H)(η^5-C5H4)(η^5-C9H6)]·(MCl2)}2[M=Zr or Ti](6,7),配体和化合物都经过核磁氢谱(1HNMR)、碳谱(13CNMR)、红外光谱(IR)及元素分析等表征,确认了化学结构.以甲基铝氧烷(MAO)为助催化剂,化合物4~7为催化剂催化丙烯聚合,考察了聚合温度、乙烯压力、铝钛或铝锆比对催化剂活性及聚合物分子量的影响.结果表明,多亚甲基桥连双核茂金属是高活性乙烯和丙烯聚合催化剂,乙烯聚合活性最高达到7.5×10^6gPE/(molZr·h)(化合物6),丙烯聚合活性达10×10^5gsPP/(molZr·h)(化合物4).所得间规聚丙烯(sPP)的间规度指数(SI,r)达到90%.在同样条件下,双核化合物的催化活性、聚合物分子量Mw(>100000)以及分子量分布(MWD>2.5)均比相应的单核化合物高(Mw<70000,MWD≤2),表明该体系中存在较强的核效应.
基金supported by the National Natural Science Foundation of China (21275014, 21375005)the Excellent Young Scientists Fund of NSFC (21322501)+2 种基金the Importation and Development of High-Caliber Talents Project of Beijing Municipal Institutions (CIT& TCD20140309)the Program for New Century Excellent Talents in University (NCET-12-0603)the Beijing Natural Science Foundation Program and Scientific Research Key Program of the Beijing Municipal Commission of Education (KZ201310005001)
文摘Binuclear iron phthalocyanine/reduced graphene oxide(bi-Fe Pc/RGO) nanocomposite with good electrocatalytic activity for ORR in alkaline medium was prepared in one step. High angle annular dark field image scanning transmission electron microscopy(HAADF-STEM) and energy dispersive X-ray spectroscopy element mapping results show bi-Fe Pc was uniformly distributed on RGO. An obvious cathodic peak located at about-0.23 V(vs. SCE) in CV and an onset potential of-0.004 V(vs. SCE) in LSV indicate the as-prepared bi-Fe Pc/RGO nanocomposite possesses high activity which is closed to Pt/C for ORR. The ORR on bi-Fe Pc/RGO nanocomposite follows four-electron transfer pathway in alkaline medium. Compared with Pt/C, there is only a slight decrease(about 0.02 V vs. SCE) for bi-Fe Pc/RGO nanocomposite when the methanol exists. The excellent activity and methanol tolerance in alkaline solutions proves that bi-Fe Pc/RGO nanocomposite could be considered as a promising cathode catalyst for alkaline fuel cells.
