Cycloaddition of CO_(2) and epoxide into cyclic carbonate is one of the most efficient ways for CO_(2) conversion with 100% atom-utilization. Metal–organic frameworks are a kind of potential heterogeneous catalysts, ...Cycloaddition of CO_(2) and epoxide into cyclic carbonate is one of the most efficient ways for CO_(2) conversion with 100% atom-utilization. Metal–organic frameworks are a kind of potential heterogeneous catalysts, however, high temperature, high pressure, and high-purity CO_(2) are still required for the reaction.Here, we report two new Zn(Ⅱ) imidazolate frameworks incoporating MoO_(4)^(2–)or WO_(4)^(2–)units, which can catalyse cycloaddition of CO_(2) and epichlorohydrin at room temperature and atomospheric pressure, giving 95% yield after 24 h in pure CO_(2) and 98% yield after 48 h in simulated flue gas(15% CO_(2)+ 85% N_(2)),respectively. For comparison, the analogic Zn(Ⅱ) imidazolate framework MAF-6 without non-3d metal oxide units showed 71% and 33% yields under the same conditions, respectively. The insightful modulation mechanisms of the MoO_(4)^(2–)unit in optimizing the electronic structure of Zn(Ⅱ) centre, facilitating the rate-determined ring opening process, and minimizing the reaction activation energy, were revealed by X-ray photoelectron spectroscopy, temperature programmed desorption and computational calculations.展开更多
As electronic packages become more compact, run at faster speeds and dissipate more heat, package designers need more effective thermal management materials. CVD diamond, because of its high thermal conductivity, low ...As electronic packages become more compact, run at faster speeds and dissipate more heat, package designers need more effective thermal management materials. CVD diamond, because of its high thermal conductivity, low dielectric loss and its great mechanical strength, is an excellent material for three dimensional （319） multichip modules （MCMs） in the next generation compact high speed computers and high power microwave components. In this paper, we have synthesized a large area freestanding diamond films and substrates, and polished diamond substrates, which make MCMs diamond film sink becomes a reality.展开更多
Holographic patterns that integrate printings and holograms into a single device have received extensive attention in optical security owing to their attractive aesthetics and concealment.However,the sophisticated str...Holographic patterns that integrate printings and holograms into a single device have received extensive attention in optical security owing to their attractive aesthetics and concealment.However,the sophisticated structures of metasurface-based optical devices require a time-consuming fabrication process,hindering the practical application of holographic patterns in optical security.In this study,a novel double-layer holographic pattern that employs simple microholes and microvoids as optical modulation units is designed and experimentally demonstrated.The two layers of the structure arrays are synchronously processed in a transparent material through a single serial-stitching of dynamic 3D spatially modulated femtosecond pulses that are proposed for the rapid fabrication of large-area multi-layered patterns.The fabricated holographic pattern appears as a dynamic grayscale image under white light incident at different angles and projects encoded holographic images under laser illumination.By transforming microholes into microcraters by ultrasonic treatment,the reconfiguration of the holographic pattern can be realized based on refractive index modulation using liquid immersion.The proposed reconfigurable holographic patterns with simple structures and visible sizes enable the recoding of multiple pieces of information,making them practical optical security elements with a wide range of applications in anticounterfeiting and information encryption.展开更多
基金supported by the National Natural Science Foundation of China (Nos. 22090061, 21731007, 21890380 and 22161021)the Guangdong Pearl River Talents Program (No. 2017BT01C161)the support of Jiangxi Province (No. jxsq2018106041)。
文摘Cycloaddition of CO_(2) and epoxide into cyclic carbonate is one of the most efficient ways for CO_(2) conversion with 100% atom-utilization. Metal–organic frameworks are a kind of potential heterogeneous catalysts, however, high temperature, high pressure, and high-purity CO_(2) are still required for the reaction.Here, we report two new Zn(Ⅱ) imidazolate frameworks incoporating MoO_(4)^(2–)or WO_(4)^(2–)units, which can catalyse cycloaddition of CO_(2) and epichlorohydrin at room temperature and atomospheric pressure, giving 95% yield after 24 h in pure CO_(2) and 98% yield after 48 h in simulated flue gas(15% CO_(2)+ 85% N_(2)),respectively. For comparison, the analogic Zn(Ⅱ) imidazolate framework MAF-6 without non-3d metal oxide units showed 71% and 33% yields under the same conditions, respectively. The insightful modulation mechanisms of the MoO_(4)^(2–)unit in optimizing the electronic structure of Zn(Ⅱ) centre, facilitating the rate-determined ring opening process, and minimizing the reaction activation energy, were revealed by X-ray photoelectron spectroscopy, temperature programmed desorption and computational calculations.
基金Supported by National Natural Science Foundation of China (No.60371006)
文摘As electronic packages become more compact, run at faster speeds and dissipate more heat, package designers need more effective thermal management materials. CVD diamond, because of its high thermal conductivity, low dielectric loss and its great mechanical strength, is an excellent material for three dimensional （319） multichip modules （MCMs） in the next generation compact high speed computers and high power microwave components. In this paper, we have synthesized a large area freestanding diamond films and substrates, and polished diamond substrates, which make MCMs diamond film sink becomes a reality.
基金National Key R&D Program of China(Grant No.2022YFB4601300)National Science Fund for Distinguished Young Scholars(Grant No.52325505)+3 种基金National Natural Science Foundation of China(NSFC)(Grant Nos.52075041 and U21A20140)Chongqing Natural Science Foundation of China(Grant No.cstc2021jcyj-cxttX0003)Joint Funds of the National Natural Science Foundation of China(Grant No.U2037205)the Beijing Outstanding Young Scientist Program(Grant No.BJJWZYJH01201910007022).
文摘Holographic patterns that integrate printings and holograms into a single device have received extensive attention in optical security owing to their attractive aesthetics and concealment.However,the sophisticated structures of metasurface-based optical devices require a time-consuming fabrication process,hindering the practical application of holographic patterns in optical security.In this study,a novel double-layer holographic pattern that employs simple microholes and microvoids as optical modulation units is designed and experimentally demonstrated.The two layers of the structure arrays are synchronously processed in a transparent material through a single serial-stitching of dynamic 3D spatially modulated femtosecond pulses that are proposed for the rapid fabrication of large-area multi-layered patterns.The fabricated holographic pattern appears as a dynamic grayscale image under white light incident at different angles and projects encoded holographic images under laser illumination.By transforming microholes into microcraters by ultrasonic treatment,the reconfiguration of the holographic pattern can be realized based on refractive index modulation using liquid immersion.The proposed reconfigurable holographic patterns with simple structures and visible sizes enable the recoding of multiple pieces of information,making them practical optical security elements with a wide range of applications in anticounterfeiting and information encryption.
