Two kinds of metal-organic frameworks(MOFs) based on Co(Ⅱ) and Fe(Ⅱ) as metal ions and trimasic acid(TMA) as organic linker were synthesized. They were used to prepare corresponding Mg H2-TM MOF(TM = Co, Fe) composi...Two kinds of metal-organic frameworks(MOFs) based on Co(Ⅱ) and Fe(Ⅱ) as metal ions and trimasic acid(TMA) as organic linker were synthesized. They were used to prepare corresponding Mg H2-TM MOF(TM = Co, Fe) composites via ball-milling. X-ray diffraction analyses show the formation of Mg2 Co and α-Fe phases in Mg H2-TMMOF composites after decomposition. Both of the well dispersed Mg2Co andα-Fe nanoparticles exhibit considerable catalytic efficiency in accelerating the sorption kinetics of Mg H2.The dehydrogenated MgH2-Fe MOF composite shows faster hydriding kinetics than the pure Mg H2 and Mg H2-CoMOF. Meanwhile, the apparent dehydrogenation activation energy(Ed) of the Mg H2-Co MOF and Mg H2-Fe MOF composites are 151.3 ± 9.4 and 142.3 ± 6.5 kJ/mol H2, both of which are lower than that of pure Mg H2(181.4 ± 9.2 kJ/mol H2). The improvement on the sorption kinetics of the Mg H2-TM MOF powders is mainly attributed to the catalytic effects of nano-sized Mg2 Co and α-Fe formed on the surface of Mg/Mg H2 particles.展开更多
A Fe modified Na2WO4 compound was synthesized by a solution impregnation method and was ball-milled with MgH2 to constitute a novel MgH2-Fe2O3/Na2WO4 composite. The effects of the Fe2O3/Na2WO4 additive on the hydrogen...A Fe modified Na2WO4 compound was synthesized by a solution impregnation method and was ball-milled with MgH2 to constitute a novel MgH2-Fe2O3/Na2WO4 composite. The effects of the Fe2O3/Na2WO4 additive on the hydrogen storage properties of MgH2 together with the corresponding mechanism were investigated. At 423 K, within the first 200 seconds, the hydrogen absorption amount of MgH2+20 wt% Fe2O3/Na2WO4 was almost 5 times that of pure MgH2. And at 573 K, its total hydrogen desorption amount was 7 times that for pure MgH2. Meanwhile, its onset dehydrogenation temperature was 110 K lower than that of pure MgH2. It was worth noting that the MgH2+20 wt% Fe/Na2WO4 presented the lower dehydrogenation reaction activation energy(Ea) of 35.9 kJ·mol^-1 compared to that of pure MgH2. The active MgWO4, Mg2 FeH6 and MgO formed during the milling process were responsible for the improvement of the hydrogen storage properties for MgH2.展开更多
The interaction of Cd2＋ with uracil,2-thiouracil,4-thiouracil and 2,4-dithiouracil have been investigated by the density functional theory（DFT） calculations.For uracil and 2,4-dithiouracil,where the two basic sites...The interaction of Cd2＋ with uracil,2-thiouracil,4-thiouracil and 2,4-dithiouracil have been investigated by the density functional theory（DFT） calculations.For uracil and 2,4-dithiouracil,where the two basic sites are the same,Cd2＋ attachment to the heteroatom at position 4 is preferred.However,for the systems where both types of basic centers,a carbonyl and a thiocarbonyl groups,are present,Cd2＋ association with sulfur is favorable.The enhanced stability of these enolic and thiol forms comes from Cd2＋ interaction with two basic sites simultaneously,which thereby triggers a significant aromatization of the ring.More significantly,the Cd2＋ binding energy with uracil and its thio-derivatives is larger than the tautomerization barriers connecting the diketo-like forms with the corresponding enolic-like tautomers.Consequently,when associated with Cd2＋,all tautomers are energetically accessible and should be observed in the gas phase.展开更多
基金supported financially by the National Natural Science Foundation of China (No. 51771112)the National Key Research & Development Project (No. 2018YFB1502104)+1 种基金the Shanghai Science and Technology Commission (No. 14JC1491600)the Shanghai Education Commission “Shuguang” Scholar Project (No. 16SG08)
文摘Two kinds of metal-organic frameworks(MOFs) based on Co(Ⅱ) and Fe(Ⅱ) as metal ions and trimasic acid(TMA) as organic linker were synthesized. They were used to prepare corresponding Mg H2-TM MOF(TM = Co, Fe) composites via ball-milling. X-ray diffraction analyses show the formation of Mg2 Co and α-Fe phases in Mg H2-TMMOF composites after decomposition. Both of the well dispersed Mg2Co andα-Fe nanoparticles exhibit considerable catalytic efficiency in accelerating the sorption kinetics of Mg H2.The dehydrogenated MgH2-Fe MOF composite shows faster hydriding kinetics than the pure Mg H2 and Mg H2-CoMOF. Meanwhile, the apparent dehydrogenation activation energy(Ed) of the Mg H2-Co MOF and Mg H2-Fe MOF composites are 151.3 ± 9.4 and 142.3 ± 6.5 kJ/mol H2, both of which are lower than that of pure Mg H2(181.4 ± 9.2 kJ/mol H2). The improvement on the sorption kinetics of the Mg H2-TM MOF powders is mainly attributed to the catalytic effects of nano-sized Mg2 Co and α-Fe formed on the surface of Mg/Mg H2 particles.
基金the financial support from Nanjing University of Science and TechnologyXi'an Modern Chemistry Research Institute+1 种基金supported by Five-Year (2011~2015) Pre-research Project (NO. 62201070102)Doctoral Innovation Program Foundation of Jiangsu Province (CXLX12 0646)
基金Funded by the National Natural Science Foundation of China(No.51771164)Scientific Research Projects in Colleges and Universities in Hebei Province,China(No.ZD2019307)+2 种基金the Fundamental Research Funds for the Central Universities(No.3142019013)the Natural Science Foundation of Hebei Province of China(No.E2019508214)the Program for Top-notch Young Talents in University of Hebei Province(No.BJ2016043)
文摘A Fe modified Na2WO4 compound was synthesized by a solution impregnation method and was ball-milled with MgH2 to constitute a novel MgH2-Fe2O3/Na2WO4 composite. The effects of the Fe2O3/Na2WO4 additive on the hydrogen storage properties of MgH2 together with the corresponding mechanism were investigated. At 423 K, within the first 200 seconds, the hydrogen absorption amount of MgH2+20 wt% Fe2O3/Na2WO4 was almost 5 times that of pure MgH2. And at 573 K, its total hydrogen desorption amount was 7 times that for pure MgH2. Meanwhile, its onset dehydrogenation temperature was 110 K lower than that of pure MgH2. It was worth noting that the MgH2+20 wt% Fe/Na2WO4 presented the lower dehydrogenation reaction activation energy(Ea) of 35.9 kJ·mol^-1 compared to that of pure MgH2. The active MgWO4, Mg2 FeH6 and MgO formed during the milling process were responsible for the improvement of the hydrogen storage properties for MgH2.
基金supported by the NNSFC (20973174 and 91122015)the Young Scientist Fund of NSFC (81001403)the Youth Innovation Fund,Institute Key Program (SZD08003) of FJIRSM
文摘The interaction of Cd2＋ with uracil,2-thiouracil,4-thiouracil and 2,4-dithiouracil have been investigated by the density functional theory（DFT） calculations.For uracil and 2,4-dithiouracil,where the two basic sites are the same,Cd2＋ attachment to the heteroatom at position 4 is preferred.However,for the systems where both types of basic centers,a carbonyl and a thiocarbonyl groups,are present,Cd2＋ association with sulfur is favorable.The enhanced stability of these enolic and thiol forms comes from Cd2＋ interaction with two basic sites simultaneously,which thereby triggers a significant aromatization of the ring.More significantly,the Cd2＋ binding energy with uracil and its thio-derivatives is larger than the tautomerization barriers connecting the diketo-like forms with the corresponding enolic-like tautomers.Consequently,when associated with Cd2＋,all tautomers are energetically accessible and should be observed in the gas phase.
