Crystallographic sites of Brönsted acids(Si-OH-Al)in zeolites,which are closely associated with the Al sites,play a significant and unique role in the catalytic application,especially when they are distributed in...Crystallographic sites of Brönsted acids(Si-OH-Al)in zeolites,which are closely associated with the Al sites,play a significant and unique role in the catalytic application,especially when they are distributed in open channel systems or confined in cavities with small pore openings.In this article,we unraveled constrained Al crystallographic sites in FER-type zeolites containing the distinct local environments(10-ring channels and ferrierite cavities)by Rietveld refinement against the powder X-ray diffraction data.Final refinement demonstrates that regardless of the types of structure-directing agents and synthetic medium utilized,T1 and/or T3 are Al-rich positions,which are further confirmed by theoretical calculations.This new finding of constrained Al sites in the FER-type zeolite can well explain its limited catalytic activity in the DME carbonylation reaction.展开更多
Multiple coordination modes are present copper coordination environment varies in the CuII-histidine complex in solution and the with pH. In this work, we have investigated the coordination geometry of Cu（His）2 comp...Multiple coordination modes are present copper coordination environment varies in the CuII-histidine complex in solution and the with pH. In this work, we have investigated the coordination geometry of Cu（His）2 complex using X-ray absorption fine structure （XAFS） analysis. Copper K-edge XAFS spectra were acquired on aqueous Cu2＋ samples with his- tidine at different pH values. The coordination environments were further confirmed by chemically modified histidine. Results show that the caboxylate groups coordinate at acidic condition, while amino and imidazole nitrogens get coordinated at higher pH. For the co- ordination geometry of Cu（His）2 in solution at physiological pH, the sixfold coordination is preferentially formed, while the fivefold coordination can co-exist in equilibrium.展开更多
At room temperature, dibenzoyl peroxide and pyridine N-oxide reacted with metallic copper powder in a mixed solvent(dichloromethane, trichloromethane and tetrahydrofuran), resulting in a binuclear copper(Ⅱ) complex. ...At room temperature, dibenzoyl peroxide and pyridine N-oxide reacted with metallic copper powder in a mixed solvent(dichloromethane, trichloromethane and tetrahydrofuran), resulting in a binuclear copper(Ⅱ) complex. [Cu (C_5H_5NO)-(C_6H_5COO)_2]_2. The structure of the complex was characterized by elemental analyses.IR spectra and X-ray single crystal analysis. The crystal is triclinic, space group P1,with cell parameters . a= 9. 262(4) ,b= 10. 697(2) , c=10. 881 (3 )A , a=59. 60( 2 ),β= 74. 83 ( 3 ) .Y = 72. 80 ( 2 )°. V= 880. 0 A￣3 . D_c = 1 . 5 20 g/cm￣3 . Z = 1 . μ= 1 2. 7 cm-1, R=0. 044 ,R_w=0. 048 for 3477 reflections with I>3σ(I), M_r=805. 78. Each copper(Ⅱ) atom is coordinated by four bridging bidentate benzoate ligands and one pyridine M-oxide.展开更多
Noble metal-reducible oxide interfaces have been regarded as one of the most active sites for water-gas shift reaction.However,the molecular reaction mechanism of water-gas shift reaction at these interfaces still rem...Noble metal-reducible oxide interfaces have been regarded as one of the most active sites for water-gas shift reaction.However,the molecular reaction mechanism of water-gas shift reaction at these interfaces still remains unclear.Herein,water-gas shift reaction at Pt-NiO interfaces has been in-situ explored using surface-enhanced Raman spectroscopy by construction of Au@Pt@NiO nanostructures.Direct Raman spectroscopic evidence demonstrates that water-gas shift reaction at Pt-NiO interfaces proceeds via an associative mechanism with the carbonate species as a key intermediate.The carbonate species is generated through the reaction of adsorbed CO with gaseous water,and its decomposition is a slow step in water-gas shift reaction.Moreover,the Pt-NiO interfaces would promote the formation of this carbonate intermediate,thus leading to a higher activity compared with pure Pt.This spectral information deepens the fundamental understanding of the reaction mechanism of water-gas shift reaction,which would promote the design of more efficient catalysts.展开更多
Eight novel lanthanide complexes： {Ln（TDA）I.5（H20）2 },, （Ln = Pr（la）, Nd（2a）） and { Ln（TDA）（Ac）（H2O）}n （Ln = Pr（1）, Nd（2） Eu（3）, Gd（4）, Tb（5）, Dy（6）; TDA = Thiophene-2,5-dicarboxylic acid...Eight novel lanthanide complexes： {Ln（TDA）I.5（H20）2 },, （Ln = Pr（la）, Nd（2a）） and { Ln（TDA）（Ac）（H2O）}n （Ln = Pr（1）, Nd（2） Eu（3）, Gd（4）, Tb（5）, Dy（6）; TDA = Thiophene-2,5-dicarboxylic acid anion） have been constructed by hydrothermal reaction. Structural analyses reveal that complexes Ia and 2a belong to the space group C2/c, exhibiting three-dimensional （3D） frame- works. Complexes 1-6 with P2t/c space group were prepared in the presence of excessive ammonium acetate, giving rise to interesting 3D frameworks different from those of la and 2a. Magnetic property studies of 4-6 reveal the weak antiferromag- netic interaction exists between adjacent Gd3＋ in 4. The complex 6 displays rather rare slow magnetization relaxation behavior in 3D frameworks.展开更多
Lowering the operating temperature of solid oxide fuel cells(SOFCs)has extensively stimulated the development of new oxide ion conductors.Here,inspired by the structural commonalities of oxide ion conductors,the inabi...Lowering the operating temperature of solid oxide fuel cells(SOFCs)has extensively stimulated the development of new oxide ion conductors.Here,inspired by the structural commonalities of oxide ion conductors,the inability to accommodate oxygen vacancies in the rigid,isolated,3-fold tetrahedral rings of SrSi/GeO_(3)-based materials,and the considerable flexibility of BO_(n) polyhedra in terms of coordination number,rotation,deformation,and linkage,we report the first borate-base family of oxide ion conductors,(Gd/Y)_(1−x)Zn_(x)BO_(3−0.5x),through combined computational prediction and experimental verification.The oxygen vacancies in(Gd/Y)BO_(3)can be accommodated by forming B_(3)O_(8)units in isolated,3-fold,tetrahedral rings of B_(3)O_(9)and transported through a cooperative mechanism of oxygen exchange between the B_(3)O_(9)and B_(3)O_(8)units,which is assisted by the intermediate opening and extending of these units.This study opens a new scientific field of the borate system for designing and discovering oxide ion conductors.展开更多
文摘Crystallographic sites of Brönsted acids(Si-OH-Al)in zeolites,which are closely associated with the Al sites,play a significant and unique role in the catalytic application,especially when they are distributed in open channel systems or confined in cavities with small pore openings.In this article,we unraveled constrained Al crystallographic sites in FER-type zeolites containing the distinct local environments(10-ring channels and ferrierite cavities)by Rietveld refinement against the powder X-ray diffraction data.Final refinement demonstrates that regardless of the types of structure-directing agents and synthetic medium utilized,T1 and/or T3 are Al-rich positions,which are further confirmed by theoretical calculations.This new finding of constrained Al sites in the FER-type zeolite can well explain its limited catalytic activity in the DME carbonylation reaction.
文摘Multiple coordination modes are present copper coordination environment varies in the CuII-histidine complex in solution and the with pH. In this work, we have investigated the coordination geometry of Cu（His）2 complex using X-ray absorption fine structure （XAFS） analysis. Copper K-edge XAFS spectra were acquired on aqueous Cu2＋ samples with his- tidine at different pH values. The coordination environments were further confirmed by chemically modified histidine. Results show that the caboxylate groups coordinate at acidic condition, while amino and imidazole nitrogens get coordinated at higher pH. For the co- ordination geometry of Cu（His）2 in solution at physiological pH, the sixfold coordination is preferentially formed, while the fivefold coordination can co-exist in equilibrium.
文摘At room temperature, dibenzoyl peroxide and pyridine N-oxide reacted with metallic copper powder in a mixed solvent(dichloromethane, trichloromethane and tetrahydrofuran), resulting in a binuclear copper(Ⅱ) complex. [Cu (C_5H_5NO)-(C_6H_5COO)_2]_2. The structure of the complex was characterized by elemental analyses.IR spectra and X-ray single crystal analysis. The crystal is triclinic, space group P1,with cell parameters . a= 9. 262(4) ,b= 10. 697(2) , c=10. 881 (3 )A , a=59. 60( 2 ),β= 74. 83 ( 3 ) .Y = 72. 80 ( 2 )°. V= 880. 0 A￣3 . D_c = 1 . 5 20 g/cm￣3 . Z = 1 . μ= 1 2. 7 cm-1, R=0. 044 ,R_w=0. 048 for 3477 reflections with I>3σ(I), M_r=805. 78. Each copper(Ⅱ) atom is coordinated by four bridging bidentate benzoate ligands and one pyridine M-oxide.
文摘Noble metal-reducible oxide interfaces have been regarded as one of the most active sites for water-gas shift reaction.However,the molecular reaction mechanism of water-gas shift reaction at these interfaces still remains unclear.Herein,water-gas shift reaction at Pt-NiO interfaces has been in-situ explored using surface-enhanced Raman spectroscopy by construction of Au@Pt@NiO nanostructures.Direct Raman spectroscopic evidence demonstrates that water-gas shift reaction at Pt-NiO interfaces proceeds via an associative mechanism with the carbonate species as a key intermediate.The carbonate species is generated through the reaction of adsorbed CO with gaseous water,and its decomposition is a slow step in water-gas shift reaction.Moreover,the Pt-NiO interfaces would promote the formation of this carbonate intermediate,thus leading to a higher activity compared with pure Pt.This spectral information deepens the fundamental understanding of the reaction mechanism of water-gas shift reaction,which would promote the design of more efficient catalysts.
基金supported by the National Natural Science Foundation of China (20971074, 91122004)Foundation for the Authors of Natural Excellent Doctoral Dissertation of China (200732)+1 种基金the Natural Science Foundation of Tianjin (10JCZDJC21700)the "100 Projects" of Creative Research for the Undergraduates of Nankai University
文摘Eight novel lanthanide complexes： {Ln（TDA）I.5（H20）2 },, （Ln = Pr（la）, Nd（2a）） and { Ln（TDA）（Ac）（H2O）}n （Ln = Pr（1）, Nd（2） Eu（3）, Gd（4）, Tb（5）, Dy（6）; TDA = Thiophene-2,5-dicarboxylic acid anion） have been constructed by hydrothermal reaction. Structural analyses reveal that complexes Ia and 2a belong to the space group C2/c, exhibiting three-dimensional （3D） frame- works. Complexes 1-6 with P2t/c space group were prepared in the presence of excessive ammonium acetate, giving rise to interesting 3D frameworks different from those of la and 2a. Magnetic property studies of 4-6 reveal the weak antiferromag- netic interaction exists between adjacent Gd3＋ in 4. The complex 6 displays rather rare slow magnetization relaxation behavior in 3D frameworks.
基金the National Natural Science Foundation of China(22090043 and 21622101)Guangxi Natural Science Foundation(2019GXNSFGA245006)for financial support+2 种基金the National Natural Science Foundation of China(21527803 and 21621061)the Ministry of Science and Technology of China(2016YFA0301004)for financial supportthe funding from China Postdoctoral Science Foundation(8206300392)。
文摘Lowering the operating temperature of solid oxide fuel cells(SOFCs)has extensively stimulated the development of new oxide ion conductors.Here,inspired by the structural commonalities of oxide ion conductors,the inability to accommodate oxygen vacancies in the rigid,isolated,3-fold tetrahedral rings of SrSi/GeO_(3)-based materials,and the considerable flexibility of BO_(n) polyhedra in terms of coordination number,rotation,deformation,and linkage,we report the first borate-base family of oxide ion conductors,(Gd/Y)_(1−x)Zn_(x)BO_(3−0.5x),through combined computational prediction and experimental verification.The oxygen vacancies in(Gd/Y)BO_(3)can be accommodated by forming B_(3)O_(8)units in isolated,3-fold,tetrahedral rings of B_(3)O_(9)and transported through a cooperative mechanism of oxygen exchange between the B_(3)O_(9)and B_(3)O_(8)units,which is assisted by the intermediate opening and extending of these units.This study opens a new scientific field of the borate system for designing and discovering oxide ion conductors.
