Molecular dynamics simulations are performed to observe the evolutions of 512 and 51262 cage-like water clusters filled with or without a methane molecule immersed in bulk liquid water at 250 K and 230 K. The lifetime...Molecular dynamics simulations are performed to observe the evolutions of 512 and 51262 cage-like water clusters filled with or without a methane molecule immersed in bulk liquid water at 250 K and 230 K. The lifetimes of these clusters are calculated according to their Lindemann index δ (t) using the criteria of δ≥0.07. For both the filled and empty clusters, we find the dynamics of bulk water determines the lifetimes of cage-like water clusters, and that the lifetime of 512 62 cage-like cluster is the same as that of 512 cage-like cluster. Although the methane molecule indeed makes the filled cage-like cluster more stable than the empty one, the empty cage-like cluster still has chance to be long-lived compared with the filled clusters. These observations support the labile cluster hypothesis on the formation mechanisms of gas hydrates.展开更多
Mesoporous carbons have been widely utilized as the sulfur host for lithium-sulfur(Li-S)batteries.The ability to engineer the porosity,wall thickness,and graphitization degree of the carbon host is essential for addre...Mesoporous carbons have been widely utilized as the sulfur host for lithium-sulfur(Li-S)batteries.The ability to engineer the porosity,wall thickness,and graphitization degree of the carbon host is essential for addressing issues that hamper commercialization of Li-S batteries,such as fast capacity decay and poor high-rate performance.In this work,highly ordered,ultrathin mesoporous graphitic-carbon frameworks(MGFs)having unique cage-like mesoporosity,derived from self-assembled Fe_(3)0_(4)nanoparticle superlattices,are demonstrated to be an excellent host for encapsulating sulfur.The resulting S@MGFs exhibit high specific capacity(1,446 mAh.g-1 at 0.15 C),good rate capability(430 mAh.g-1 at 6 C),and exceptional cycling stability(-0.049%capacity decay per cycle at 1 C)when used as Li-S cathodes.The superior electrochemical performance of the S@MGFs is attributed to the many unique and advantageous structural features of MGFs.In addition to the interconnected,ultrathin graphitic-carbon framework that ensures rapid electron and lithium-ion transport,the microporous openings between adjacent mesopores efficiently suppress the diffusion of polysulfides,leading to improved capacity retention even at high current densities.展开更多
Cage-like octa(trimethylsiloxy)silsesquioxane [(Me3SiO)SiO1.5]8 has been synthesized via the trimethylsilylation of cubic tetramethylammonium silicate octamer [(Me4NO)-SiO1.5]8 with chlorotrimethylsilane. The silicate...Cage-like octa(trimethylsiloxy)silsesquioxane [(Me3SiO)SiO1.5]8 has been synthesized via the trimethylsilylation of cubic tetramethylammonium silicate octamer [(Me4NO)-SiO1.5]8 with chlorotrimethylsilane. The silicate octamer can be selectively formed by the reaction of tetraethoxysilane Si(OEt)4 with aqueous tetramethylammonium hydroxide in equal展开更多
Coordination polymeric solid, {[Ag 2 (bpp) 2 (H 2 O) 2 ](chd)·9H 2 O} n (1) (bpp = 1,3-bis(4-pyridyl) propane, H 2 chd = 1,4-cyclo-hexanedicarboxylic acid), has been obtained by the solution phase ultrasonic synt...Coordination polymeric solid, {[Ag 2 (bpp) 2 (H 2 O) 2 ](chd)·9H 2 O} n (1) (bpp = 1,3-bis(4-pyridyl) propane, H 2 chd = 1,4-cyclo-hexanedicarboxylic acid), has been obtained by the solution phase ultrasonic synthesis techniques. The structure established through X-ray structural analysis shows that the compound traps an interesting 1D water tape built by the alternating "three-pointed star" cage-like pentameric and D 2h tetrameric clusters (C2/c, Z = 4; a = 30.37(2) , b = 9.271(5) , and c = 18.89(1) ; β = 128.47°; V = 4164(4) 3 ). The novelty of the present complex is the rarely crystallographic example of the cage-shaped water pentamer, which is usually ascribed to a less-stable species. A first-principle density functional theory (DFT) calculation demonstrates that the interconnectivity between cage-like pentamers and D 2h tetramers is beneficial for contribution to the structural stabilization of these less-stable water cluster species.展开更多
A chemical investigation on Sporormiella sp.led to the isolation and structural elucidation of tripodalsporormielones Ae C(1-3),a new class of polyketide possessing unprecedented cage-like skeletons with polyvdent bri...A chemical investigation on Sporormiella sp.led to the isolation and structural elucidation of tripodalsporormielones Ae C(1-3),a new class of polyketide possessing unprecedented cage-like skeletons with polyvdent bridged and fused ring systems.These polyketides with cage-like skeletons were characterized as a high non-protonated carbon-containing system,which resulted in few HMBC correlations observed and made the accurate structures hard to be obtained by NMR.Especially,some signals of non-protonated sp;carbons are weak and even unobservable in compound 1.In order to establish the structure of 1,the calculated NMR with DP4 evaluation was applied to determine the structure from the plausible structure candidates obtained from the detailed NMR analysis.Based on NMR experiments and calculated NMR,the structures of isolated compounds were established and confirmed by X-ray technology.Through chiral isolation,the optically pure enantiomers of 1 and 3 were obtained,and their absolute configurations were determined based on ECD quantum chemical calculation.Based on the isolated compounds and our previous work,1-3 would be derived from 3-methylorcinaldehyde,and their plausible biosynthetic mechanism was proposed.Furthermore,1 exhibited obvious short-term memory improvement activity on an Alzheimer’s disease fly model.展开更多
A novel Pd（ll） organometal catalyst with three-dimensional （3D） cage-like la3d cubic mesoporous structure and high surface area was prepared. In comparison with the corresponding catalyst with two-dimensional （2D...A novel Pd（ll） organometal catalyst with three-dimensional （3D） cage-like la3d cubic mesoporous structure and high surface area was prepared. In comparison with the corresponding catalyst with two-dimensional （2D） P6mm hexagonal mesoporous structure, the as-prepared catalyst exhibited higher activities in the water-medium Suzuki coupling reactions owing to the diminished diffusion limit. It showed comparable efficiencies with the Pd（PPh3）2C12 homogeneous catalyst and could be easily recycled and reused for five times without significant loss of activity.展开更多
Polymer-based aerogels are emerging as promising candidates for lightweight and high performance electromagnetic(EM)wave absorption materials.In this study,an ultralight and rigid poly(p-phenylene benzobisoxazole)nano...Polymer-based aerogels are emerging as promising candidates for lightweight and high performance electromagnetic(EM)wave absorption materials.In this study,an ultralight and rigid poly(p-phenylene benzobisoxazole)nanofiber(PNF)based composite aerogel with excellent EM wave absorption performance was fabricated with cobalt-nickel alloy(CoNi)nanoparticles and carbon nanotubes(CNTs)as magnetic and conductive fillers,respectively.A CNT/PNF composite aerogel was first prepared through a sol-gel and freeze-drying method,and then CoNi nanoparticles were introduced therein through hydrothermal reaction and thermal annealing to obtain the CoNi/CNT/PNF aerogel.CNTs and PNFs were interwoven and constructed a three-dimensional conductive/magnetic cage-like skeleton structure decorating with magnetic CoNi nanoparticles.The cage-like skeleton structure allowed the dissipation of EM waves through multiple mechanisms encompassing conduction loss,magnetic loss,multiple reflection,scattering,and absorption.When its thickness was 4 mm,the CoNi/CNT/PNF aerogel showed a minimal reflection loss of-44.7 dB(at 6.88 GHz),and its broad effective absorption bandwidth covered the entire X-band and Ku-band and most of the C-band(12.32 GHz,from 5.68 GHz to 18 GHz).In addition,the rigid aerogel exhibited an ultralow density(0.107 g/cm^(3)),excellent thermal insulation,and flame retardancy,demonstrating its potential application as a high-performance EM wave absorption material in the fields of aerospace and national defense.展开更多
锂硫电池由于其高理论比容量而备受瞩目,然而其商业化进程仍受到中间产物的穿梭效应、硫的绝缘性和正极体积膨胀等一系列问题的阻碍.为了有效抑制穿梭效应,通过水热法合成了一种以钴和镍为主体的笼状中空双金属硫化物(Ni_(3-x)Co_(x)S_(...锂硫电池由于其高理论比容量而备受瞩目,然而其商业化进程仍受到中间产物的穿梭效应、硫的绝缘性和正极体积膨胀等一系列问题的阻碍.为了有效抑制穿梭效应,通过水热法合成了一种以钴和镍为主体的笼状中空双金属硫化物(Ni_(3-x)Co_(x)S_(4)),并将其作为隔膜部分组装到Li-S电池中.其中空结构的特点为氧化还原反应提供了足够的活性位点,进而可以达到更大的比容量,本工作发现,采用最佳比例(2∶1)的笼状Ni_(3-x)Co_(x)S_(4)材料能够通过物理吸附和化学固定促进多硫化物的转化,有效限制多硫化物的穿梭,提高电导率,并促进锂离子的扩散.实验结果显示,笼状Ni_(3-x)Co_(x)S_(4)材料表现出优异的性能,包括在0.1 C下达到1184.3 mAh g^(-1)的初始容量以及在0.2 C循环200圈后仍保持564.4 mAh g^(-1)的比容量.展开更多
A new tripod polyaromatic acid ligand H3TCM（H3TCM={2,4,6-tris1,3,5-trimethylbenzene}） and its binuclear rare earth complex \·2DMF were prepared and the structure of complex was characterized by single crystal X...A new tripod polyaromatic acid ligand H3TCM（H3TCM={2,4,6-tris1,3,5-trimethylbenzene}） and its binuclear rare earth complex \·2DMF were prepared and the structure of complex was characterized by single crystal X-ray diffraction. The complex crystallizes in triclinic crystal system, space group P1 with a=1.123 3（2） nm, b=1.374 1（2） nm, （c=）1.731 8（2） nm, α=78.19（1）°, β=80.02（1）°, γ=80.08（1）°, V=2.550 8（7） nm3, Z=1, （R=）0.035 8, wR=0.080 3. Two TCM ligands that are both in cis, cis, cis-conformations adopt face-to-face orientation and are joined together by two La3+ to a novel binuclear cage-like structure. Two DMF molecules are encapsulated in this cage by coordination. In addition, the other two free DMF molecules are embedded in the channels from the packing of these units along a and b axises.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.40102005 and No.49725205).
文摘Molecular dynamics simulations are performed to observe the evolutions of 512 and 51262 cage-like water clusters filled with or without a methane molecule immersed in bulk liquid water at 250 K and 230 K. The lifetimes of these clusters are calculated according to their Lindemann index δ (t) using the criteria of δ≥0.07. For both the filled and empty clusters, we find the dynamics of bulk water determines the lifetimes of cage-like water clusters, and that the lifetime of 512 62 cage-like cluster is the same as that of 512 cage-like cluster. Although the methane molecule indeed makes the filled cage-like cluster more stable than the empty one, the empty cage-like cluster still has chance to be long-lived compared with the filled clusters. These observations support the labile cluster hypothesis on the formation mechanisms of gas hydrates.
基金A.G.D.acknowledges the financial support from the National Basic Research Program of China(No.2014CB845602)Natural National Science Foundation of China(No.21373052)+2 种基金Shanghai International Science and Technology Cooperation Project(No.15520720100)D.Y.is grateful for financial support from Natural National Science Foundation of China(Nos.51373035,51373040,51573030,and 51573028)International Science and Technology Cooperation Program of China(No.2014DFE40130).
文摘Mesoporous carbons have been widely utilized as the sulfur host for lithium-sulfur(Li-S)batteries.The ability to engineer the porosity,wall thickness,and graphitization degree of the carbon host is essential for addressing issues that hamper commercialization of Li-S batteries,such as fast capacity decay and poor high-rate performance.In this work,highly ordered,ultrathin mesoporous graphitic-carbon frameworks(MGFs)having unique cage-like mesoporosity,derived from self-assembled Fe_(3)0_(4)nanoparticle superlattices,are demonstrated to be an excellent host for encapsulating sulfur.The resulting S@MGFs exhibit high specific capacity(1,446 mAh.g-1 at 0.15 C),good rate capability(430 mAh.g-1 at 6 C),and exceptional cycling stability(-0.049%capacity decay per cycle at 1 C)when used as Li-S cathodes.The superior electrochemical performance of the S@MGFs is attributed to the many unique and advantageous structural features of MGFs.In addition to the interconnected,ultrathin graphitic-carbon framework that ensures rapid electron and lithium-ion transport,the microporous openings between adjacent mesopores efficiently suppress the diffusion of polysulfides,leading to improved capacity retention even at high current densities.
文摘Cage-like octa(trimethylsiloxy)silsesquioxane [(Me3SiO)SiO1.5]8 has been synthesized via the trimethylsilylation of cubic tetramethylammonium silicate octamer [(Me4NO)-SiO1.5]8 with chlorotrimethylsilane. The silicate octamer can be selectively formed by the reaction of tetraethoxysilane Si(OEt)4 with aqueous tetramethylammonium hydroxide in equal
基金supported by the National Natural Science Foundation of China (50971063)the Natural Science Foundation of Fujian Province (2003F006, 2010J01042, 2011J01047)+1 种基金the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry of Chinathe Startup Package Funding of Huaqiao University (10BS210) for supporting
文摘Coordination polymeric solid, {[Ag 2 (bpp) 2 (H 2 O) 2 ](chd)·9H 2 O} n (1) (bpp = 1,3-bis(4-pyridyl) propane, H 2 chd = 1,4-cyclo-hexanedicarboxylic acid), has been obtained by the solution phase ultrasonic synthesis techniques. The structure established through X-ray structural analysis shows that the compound traps an interesting 1D water tape built by the alternating "three-pointed star" cage-like pentameric and D 2h tetrameric clusters (C2/c, Z = 4; a = 30.37(2) , b = 9.271(5) , and c = 18.89(1) ; β = 128.47°; V = 4164(4) 3 ). The novelty of the present complex is the rarely crystallographic example of the cage-shaped water pentamer, which is usually ascribed to a less-stable species. A first-principle density functional theory (DFT) calculation demonstrates that the interconnectivity between cage-like pentamers and D 2h tetramers is beneficial for contribution to the structural stabilization of these less-stable water cluster species.
基金financially supported by grants from National Key Research and Development Program of China(2018YF A0903200/2018YFA0903201)the National Natural Science Foundation of China(81925037 and 81973213)+5 种基金Chang Jiang Scholars Program(Young Scholar)from the Ministry of Education of China(Hao Gao,2017)National High-level Personnel of Special Support Program(2017RA2259,China)the 111 Project of Ministry of Education of the People’s Republic of China(B13038)the Guangdong Natural Science Funds for Distinguished Young Scholar(2017A03036027,China)Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program(2017BT01Y036,China)K.C.Wong Education Foundation(Hao Gao,2016,China)。
文摘A chemical investigation on Sporormiella sp.led to the isolation and structural elucidation of tripodalsporormielones Ae C(1-3),a new class of polyketide possessing unprecedented cage-like skeletons with polyvdent bridged and fused ring systems.These polyketides with cage-like skeletons were characterized as a high non-protonated carbon-containing system,which resulted in few HMBC correlations observed and made the accurate structures hard to be obtained by NMR.Especially,some signals of non-protonated sp;carbons are weak and even unobservable in compound 1.In order to establish the structure of 1,the calculated NMR with DP4 evaluation was applied to determine the structure from the plausible structure candidates obtained from the detailed NMR analysis.Based on NMR experiments and calculated NMR,the structures of isolated compounds were established and confirmed by X-ray technology.Through chiral isolation,the optically pure enantiomers of 1 and 3 were obtained,and their absolute configurations were determined based on ECD quantum chemical calculation.Based on the isolated compounds and our previous work,1-3 would be derived from 3-methylorcinaldehyde,and their plausible biosynthetic mechanism was proposed.Furthermore,1 exhibited obvious short-term memory improvement activity on an Alzheimer’s disease fly model.
文摘A novel Pd（ll） organometal catalyst with three-dimensional （3D） cage-like la3d cubic mesoporous structure and high surface area was prepared. In comparison with the corresponding catalyst with two-dimensional （2D） P6mm hexagonal mesoporous structure, the as-prepared catalyst exhibited higher activities in the water-medium Suzuki coupling reactions owing to the diminished diffusion limit. It showed comparable efficiencies with the Pd（PPh3）2C12 homogeneous catalyst and could be easily recycled and reused for five times without significant loss of activity.
基金the National Natural Science Foundation of China(52203100)Shaanxi Province Key Research and Development Plan Project(2024GX-YBXM-386)+3 种基金the Innovation Capability Support Program of Shaanxi(2024RS-CXTD-57)Natural Science Foundation of Chongqing,China(2023NSCQ-MSX2682)Undergraduate Innovation&Business Program of Northwestern Polytechnical University(S202310699322)the Analytical&Testing Center of Northwestern Polytechnical University for SEM tests performed in this work.
文摘Polymer-based aerogels are emerging as promising candidates for lightweight and high performance electromagnetic(EM)wave absorption materials.In this study,an ultralight and rigid poly(p-phenylene benzobisoxazole)nanofiber(PNF)based composite aerogel with excellent EM wave absorption performance was fabricated with cobalt-nickel alloy(CoNi)nanoparticles and carbon nanotubes(CNTs)as magnetic and conductive fillers,respectively.A CNT/PNF composite aerogel was first prepared through a sol-gel and freeze-drying method,and then CoNi nanoparticles were introduced therein through hydrothermal reaction and thermal annealing to obtain the CoNi/CNT/PNF aerogel.CNTs and PNFs were interwoven and constructed a three-dimensional conductive/magnetic cage-like skeleton structure decorating with magnetic CoNi nanoparticles.The cage-like skeleton structure allowed the dissipation of EM waves through multiple mechanisms encompassing conduction loss,magnetic loss,multiple reflection,scattering,and absorption.When its thickness was 4 mm,the CoNi/CNT/PNF aerogel showed a minimal reflection loss of-44.7 dB(at 6.88 GHz),and its broad effective absorption bandwidth covered the entire X-band and Ku-band and most of the C-band(12.32 GHz,from 5.68 GHz to 18 GHz).In addition,the rigid aerogel exhibited an ultralow density(0.107 g/cm^(3)),excellent thermal insulation,and flame retardancy,demonstrating its potential application as a high-performance EM wave absorption material in the fields of aerospace and national defense.
文摘锂硫电池由于其高理论比容量而备受瞩目,然而其商业化进程仍受到中间产物的穿梭效应、硫的绝缘性和正极体积膨胀等一系列问题的阻碍.为了有效抑制穿梭效应,通过水热法合成了一种以钴和镍为主体的笼状中空双金属硫化物(Ni_(3-x)Co_(x)S_(4)),并将其作为隔膜部分组装到Li-S电池中.其中空结构的特点为氧化还原反应提供了足够的活性位点,进而可以达到更大的比容量,本工作发现,采用最佳比例(2∶1)的笼状Ni_(3-x)Co_(x)S_(4)材料能够通过物理吸附和化学固定促进多硫化物的转化,有效限制多硫化物的穿梭,提高电导率,并促进锂离子的扩散.实验结果显示,笼状Ni_(3-x)Co_(x)S_(4)材料表现出优异的性能,包括在0.1 C下达到1184.3 mAh g^(-1)的初始容量以及在0.2 C循环200圈后仍保持564.4 mAh g^(-1)的比容量.
文摘A new tripod polyaromatic acid ligand H3TCM（H3TCM={2,4,6-tris1,3,5-trimethylbenzene}） and its binuclear rare earth complex \·2DMF were prepared and the structure of complex was characterized by single crystal X-ray diffraction. The complex crystallizes in triclinic crystal system, space group P1 with a=1.123 3（2） nm, b=1.374 1（2） nm, （c=）1.731 8（2） nm, α=78.19（1）°, β=80.02（1）°, γ=80.08（1）°, V=2.550 8（7） nm3, Z=1, （R=）0.035 8, wR=0.080 3. Two TCM ligands that are both in cis, cis, cis-conformations adopt face-to-face orientation and are joined together by two La3+ to a novel binuclear cage-like structure. Two DMF molecules are encapsulated in this cage by coordination. In addition, the other two free DMF molecules are embedded in the channels from the packing of these units along a and b axises.
