Covalent organic frameworks(COFs), as an emerging class of porous crystalline materials constructed by covalent links between the building monomers, have gained tremendous attention. Over the past 15 years, COFs have ...Covalent organic frameworks(COFs), as an emerging class of porous crystalline materials constructed by covalent links between the building monomers, have gained tremendous attention. Over the past 15 years, COFs have made rapid progress and substantial development in the chemistry and materials fields. However, the synthesis of COFs has been dominated by solvothermal methods for a long time and it usually involves high temperature, high pressure and toxic organic solvents, which created many challenges for environmental considerations. Recently,the exploration of new approaches for facile fabrication of COFs has aroused extensive interest. Hence, in this review, we comprehensively describe the synthetic strategies of COFs from the aspects of nonconventional heating methods and reaction media. In addition, the advantages,limitations and properties of the preparation methods are compared. Finally, we outline the main challenges and development prospects of the synthesis of COFs in the future and propose some possible solutions.展开更多
Carbon dioxide as both a selective agent and reaction media in the palladium-catalyzed Ullmann-type coupling has been described. The results showed that aryl chlorides could be easily activated in the presence of carb...Carbon dioxide as both a selective agent and reaction media in the palladium-catalyzed Ullmann-type coupling has been described. The results showed that aryl chlorides could be easily activated in the presence of carbon diox-ide and the chemoselectivity shifted toward the palladium-catalyzed Ullmann-type coupling reaction. In liquid car-bon dioxide, homocoupling reactions of aryl halides, including less reactive aryl chlorides, were carried out smoothly in moderate to good yields using Pd/C, zinc, and H2O as the catalytic system at room temperature.展开更多
Taking into consideration the gas compressibility and chemical reaction reversibility, a model was developed to study the interactions between gas flow and chemical reaction in porous media and resolved by the finite ...Taking into consideration the gas compressibility and chemical reaction reversibility, a model was developed to study the interactions between gas flow and chemical reaction in porous media and resolved by the finite volume method on the basis of the gas-solid reaction aA(g)+bB(s)cC(g)+dD(s).The numerical analysis shows that the equilibrium constant is an important factor influencing the process of gas-solid reaction. The stoichiometric coefficients, molar masses of reactant gas, product gas and inert gas are the main factors influencing the density of gas mixture. The equilibrium constant influences the gas flow in porous media obviously when the stoichiometric coefficients satisfy a/c≠1.展开更多
Research on the reaction mechanism of ethanol oxidation reaction(EOR) is important for the development of highly active EOR electro-catalysts. One of the main difficulties in the EOR study is the quantitative analysis...Research on the reaction mechanism of ethanol oxidation reaction(EOR) is important for the development of highly active EOR electro-catalysts. One of the main difficulties in the EOR study is the quantitative analysis of the non-volatile products. Conventional on-line electrochemical flowing transmission infrared spectroscopy(ETIRS) can only collect a part of the carbonate products of EOR in alkaline media, making the further quantitative study impossible. Herein, a new ETIRS system has been designed and prepared by employing a cation-exchange membrane(Nafion) in the sampling hood. The using of the Nafion membrane can prevent the anions crossing over by confining the generated carbonates in the sampling hood without diffusing into the bulk electrolyte. Therefore, the collection efficiency of the carbonate products as well as the test accuracy of the carbonate current efficiency has been significantly improved. The result of CO stripping reaction shows that ca. 100% of the carbonate product is able to be collected in alkaline media by this new system. The influence of the experimental temperature to the carbonate current efficiency has been further studied on Pt/C toward EOR in alkaline media.展开更多
This study aimed to investigate the protective effect of oral steroid premedication in terms of adverse reactions to non-ionic contrast media. We investigated the incidence of adverse reactions among patients who unde...This study aimed to investigate the protective effect of oral steroid premedication in terms of adverse reactions to non-ionic contrast media. We investigated the incidence of adverse reactions among patients who underwent contrast-enhanced computed tomography. Patients in the premedication group took 30 mg of prednisolone orally the night before and on the morning of the scheduled computed tomography. Sixty-five patients received the same contrast media. Among them, 56 took prednisolone orally prior to the procedure (premedication without change of contrast media group) and nine without premedication (no premedication and no change of contrast media group). In total, 379 patients received different contrast media. Among them, 340 took prednisolone orally (premedication with change of contrast media group), while 39 did not take the premedication (no premedication with change of contrast media group). The adverse reaction rates in the premedication with change of contrast media and no premedication with change of contrast media groups were 1.8% (6/340 cases) and 2.6% (1/39 cases) (P = 0.54), respectively. The incidence of adverse reaction after the administration of non-ionic iodinated contrast media did not differ significantly based on whether an oral steroid was administered prior to compute tomography. Our evaluation is limited due to the small sample size of the contrast media-changed group. However, even if premedication with steroids is effective, it may only result in an adverse reaction reduction rate of ≤3%.展开更多
Promoted by active indium produced in situ by Sm/InCl3 ?4H2O system, arylidenecyano- acetates undergo reductive cyclodimerization to afford cyclopentamine derivatives with high stereoselectivity under mild conditions ...Promoted by active indium produced in situ by Sm/InCl3 ?4H2O system, arylidenecyano- acetates undergo reductive cyclodimerization to afford cyclopentamine derivatives with high stereoselectivity under mild conditions in aqueous media.展开更多
基金supported by the National Natural Science Foundation of China (Nos. 21822407 and 22074154)Youth Innovation Promotion Association CAS (2021420)the Foundation for Sci & Tech Research Project of Gansu Province (20JR10RA045 and 20JR5RA573)。
文摘Covalent organic frameworks(COFs), as an emerging class of porous crystalline materials constructed by covalent links between the building monomers, have gained tremendous attention. Over the past 15 years, COFs have made rapid progress and substantial development in the chemistry and materials fields. However, the synthesis of COFs has been dominated by solvothermal methods for a long time and it usually involves high temperature, high pressure and toxic organic solvents, which created many challenges for environmental considerations. Recently,the exploration of new approaches for facile fabrication of COFs has aroused extensive interest. Hence, in this review, we comprehensively describe the synthetic strategies of COFs from the aspects of nonconventional heating methods and reaction media. In addition, the advantages,limitations and properties of the preparation methods are compared. Finally, we outline the main challenges and development prospects of the synthesis of COFs in the future and propose some possible solutions.
基金the National Natural Science Foundation of China (No. 20202002), Hunan Province Department of Education (No. 02C211) and Hunan Normal University (2001).
文摘Carbon dioxide as both a selective agent and reaction media in the palladium-catalyzed Ullmann-type coupling has been described. The results showed that aryl chlorides could be easily activated in the presence of carbon diox-ide and the chemoselectivity shifted toward the palladium-catalyzed Ullmann-type coupling reaction. In liquid car-bon dioxide, homocoupling reactions of aryl halides, including less reactive aryl chlorides, were carried out smoothly in moderate to good yields using Pd/C, zinc, and H2O as the catalytic system at room temperature.
基金Projects(51304035,50974030)supported by the National Natural Science Foundation of ChinaProject(20110491512)supported by the Postdoctoral Science Foundation of China+2 种基金Project(20130042120034)supported by the Specialized Research Fund for the Doctoral Program of Higher Education(New Teachers),ChinaProject(120401008)supported by the Fundamental Research Funds for Central Universities,ChinaProject(L20150173)supported by the Scientific Research Fund of Liaoning Provincial Education Department,China
文摘Taking into consideration the gas compressibility and chemical reaction reversibility, a model was developed to study the interactions between gas flow and chemical reaction in porous media and resolved by the finite volume method on the basis of the gas-solid reaction aA(g)+bB(s)cC(g)+dD(s).The numerical analysis shows that the equilibrium constant is an important factor influencing the process of gas-solid reaction. The stoichiometric coefficients, molar masses of reactant gas, product gas and inert gas are the main factors influencing the density of gas mixture. The equilibrium constant influences the gas flow in porous media obviously when the stoichiometric coefficients satisfy a/c≠1.
基金supported by the National Natural Science Foundation of China(21872108 , 21573167 , 21633008 and 91545205)the National Key Research and Development Program (2016YFB0101203)the Fundamental Research Funds for the Central Universities (2014203020207)
文摘Research on the reaction mechanism of ethanol oxidation reaction(EOR) is important for the development of highly active EOR electro-catalysts. One of the main difficulties in the EOR study is the quantitative analysis of the non-volatile products. Conventional on-line electrochemical flowing transmission infrared spectroscopy(ETIRS) can only collect a part of the carbonate products of EOR in alkaline media, making the further quantitative study impossible. Herein, a new ETIRS system has been designed and prepared by employing a cation-exchange membrane(Nafion) in the sampling hood. The using of the Nafion membrane can prevent the anions crossing over by confining the generated carbonates in the sampling hood without diffusing into the bulk electrolyte. Therefore, the collection efficiency of the carbonate products as well as the test accuracy of the carbonate current efficiency has been significantly improved. The result of CO stripping reaction shows that ca. 100% of the carbonate product is able to be collected in alkaline media by this new system. The influence of the experimental temperature to the carbonate current efficiency has been further studied on Pt/C toward EOR in alkaline media.
文摘This study aimed to investigate the protective effect of oral steroid premedication in terms of adverse reactions to non-ionic contrast media. We investigated the incidence of adverse reactions among patients who underwent contrast-enhanced computed tomography. Patients in the premedication group took 30 mg of prednisolone orally the night before and on the morning of the scheduled computed tomography. Sixty-five patients received the same contrast media. Among them, 56 took prednisolone orally prior to the procedure (premedication without change of contrast media group) and nine without premedication (no premedication and no change of contrast media group). In total, 379 patients received different contrast media. Among them, 340 took prednisolone orally (premedication with change of contrast media group), while 39 did not take the premedication (no premedication with change of contrast media group). The adverse reaction rates in the premedication with change of contrast media and no premedication with change of contrast media groups were 1.8% (6/340 cases) and 2.6% (1/39 cases) (P = 0.54), respectively. The incidence of adverse reaction after the administration of non-ionic iodinated contrast media did not differ significantly based on whether an oral steroid was administered prior to compute tomography. Our evaluation is limited due to the small sample size of the contrast media-changed group. However, even if premedication with steroids is effective, it may only result in an adverse reaction reduction rate of ≤3%.
基金supported by the National Natural Science Foundation of China(72293573,72104226)the Research Topic of Securities Futures Industry Standard(BZKT-2022-041)Anhui Province 2022 Annual New Era Education Quality Project(Postgraduate Education)(2022zyxwjxalk003).
文摘Promoted by active indium produced in situ by Sm/InCl3 ?4H2O system, arylidenecyano- acetates undergo reductive cyclodimerization to afford cyclopentamine derivatives with high stereoselectivity under mild conditions in aqueous media.
