Disintegration or redispersion of supported sintered gold nanoparticles （Au NPs） in the presence of alkyl halide can give catalyst regeneration or redispersion of sintered Au catalysts. The selectivity of alkyl hali...Disintegration or redispersion of supported sintered gold nanoparticles （Au NPs） in the presence of alkyl halide can give catalyst regeneration or redispersion of sintered Au catalysts. The selectivity of alkyl halides, temperature and size distributions were investigated to elucidate the redispersion of Au NPs during halide-induced decomposition. This study proved that the alkyl halide induced the redispersion of sintered Au NPs which depended on the R-X （X = I, Br, CI） bond dissociation energy （BDE） and thus provided a simple descriptor for the regeneration of inactive supported Au cata- lysts. A correlation between the BDE of R-X and dispersion efficiency was established. The tendency for disintegration and redispersion followed the R-X BDE of the alkyl halide. Compared to alkyl chlorides and bromides, iodides were more efficient for redispersing sintered Au NPs. As a descriptor, the BDE of R-I played a crucial role in particle redispersion. These findings provided in- sights into the mechanism of organic halide-induced Au NP disintegration and the effect of the hal- ide type on the redispersion of sintered catalysts.展开更多
Due to the advantages of high surface areas, large pore volumes and pore sizes, abundant nitrogen content that favored the metal-support interactions, N-doped ordered mesoporous carbons are regarded as a kind ...Due to the advantages of high surface areas, large pore volumes and pore sizes, abundant nitrogen content that favored the metal-support interactions, N-doped ordered mesoporous carbons are regarded as a kind of fascinating and potential support for the synthesis of effective supported cat-alysts. Here, a N-doped ordered mesoporous carbon with a high N content （9.58 wt%）, high surface area （417 m^2/g）, and three-dimensional cubic structure was synthesized successfully and used as an effective support for immobilizing Pt nanoparticles （NPs）. The positive effects of nitrogen on the metal particle size enabled ultrasmall Pt NPs （about 1.0 ± 0.5 nm） to be obtained. Moreover, most of the Pt NPs are homogeneously dispersed in the mesoporous channels. However, using the ordered mesoporous carbon without nitrogen as support, the particles were larger （4.4 ± 1.7 nm） and many Pt NPs were distributed on the external surface, demonstrating the important role of the nitrogen species. The obtained N-doped ordered mesoporous material supported catalyst showed excellent catalytic activity （conversion 100%） and selectivity （〉99%） in the hydrogenation of halogenated nitrobenzenes under mild conditions. These values are much higher than those achieved using a commercial Pt/C catalyst （conversion 89% and selectivity 90%）. This outstanding catalytic perfor-mance can be attributed to the synergetic effects of the mesoporous structure, N-functionalized support, and stabilized ultrasmall Pt NPs. Moreover, such supported catalyst also showed excellent catalytic performance in the hydrogenation of other halogenated nitrobenzenes and nitroarenes. In addition, the stability of the multifunctional catalyst was excellent and it could be reused more than 10 times without significant losses of activity and selectivity. Our results conclusively show that a N-doped carbon support enable the formation of ultrafine metal NPs and improve the reaction ac-tivity and selectivity.展开更多
A straightforward protocol using readily available aromatic amines,N,N,N',N'-tetramethyl-p-phenylenediamine or N,N,N',N'-tetramethylbenzidine,as photocatalysts was developed for theefficient hydrodehal...A straightforward protocol using readily available aromatic amines,N,N,N',N'-tetramethyl-p-phenylenediamine or N,N,N',N'-tetramethylbenzidine,as photocatalysts was developed for theefficient hydrodehalogenation of organic halides,such as 4'-bromoacetophenone,polyfluoroarenes,cholorobenzene,and 2,2',4,4'-tetrabromodiphenyl ether(a resistant and persistent organic pollu-tant).The strongly reducing singlet excited states of the amines enabled diffusion-controlled disso-ciative electron transfer to effectively cleave carbon-halogen bonds,followed by radical hydrogena-tion.Diisopropylethylamine served as the terminal electron/proton donor and regenerated theamine sensitizers.展开更多
The selective hydrogenation of halogenated nitrobenzene over noble metal catalysts(Pd, Pt, and Ir) has attracted much attention owing to its high efficiency and environmental friendliness. However, the effect of size ...The selective hydrogenation of halogenated nitrobenzene over noble metal catalysts(Pd, Pt, and Ir) has attracted much attention owing to its high efficiency and environmental friendliness. However, the effect of size on the catalytic performance varies among different metal catalysts. In this study, sub-nano(<3 nm) Ir and Pd particles were prepared, and their catalytic properties for hydrogenation of halogenated nitrobenzene were evaluated.Results show that high selectivity(N 99%) was achieved over small Ir nanoparticles, in which the selectivity over the Pd with same size was much lower than that on Ir nanoparticles. Meanwhile, Ir and Pd have different hydrogen consumption rates and reaction rates. Density functional theory calculations showed that p-chloronitrobenzene(CNB) has different adsorption properties on Ir and Pd. The distance between oxygen(cholorine) and Ir is much shorter(longer) than that between oxygen and Pd. The reaction barriers of dechlorination of p-CNB and p-chloroaniline over different Ir models are much larger than those on Pd. Especially,lower coordination of Ir leads to larger barriers of dechlorination reaction. These theoretical results explain the difference between Ir and Pd on hydrogenation of halogenated nitrobenzene.展开更多
Tandem water electrolysis for the transformation of universal feedstock to value-added chemicals integrated with hydrogen generation and in situ utilization is a promising approach to address the economic challenges o...Tandem water electrolysis for the transformation of universal feedstock to value-added chemicals integrated with hydrogen generation and in situ utilization is a promising approach to address the economic challenges of electrochemical hydrogen evolution and storage.Herein,we present the controllable electrocatalytic deuteration of halides using inexpensive and reusable heavy water(D2 O)as a D-source for the preparation of valuable D-labelled chemicals and pharmaceuticals under mild conditions.This electrochemical deuteration method with high efficiency and selectivity furnishes a series of D-labelled chemicals and pharmaceuticals in high yields with excellent D-incorporation.The reaction efficiency and selectivity,that is,the precise substitution of deuterium atoms at different halogen positions,can be tuned by varying the applied voltages.The results show the great potential of green and economical electrocatalytic methods for producing value-added fine chemicals in addition to hydrogen evolution.展开更多
文摘Disintegration or redispersion of supported sintered gold nanoparticles （Au NPs） in the presence of alkyl halide can give catalyst regeneration or redispersion of sintered Au catalysts. The selectivity of alkyl halides, temperature and size distributions were investigated to elucidate the redispersion of Au NPs during halide-induced decomposition. This study proved that the alkyl halide induced the redispersion of sintered Au NPs which depended on the R-X （X = I, Br, CI） bond dissociation energy （BDE） and thus provided a simple descriptor for the regeneration of inactive supported Au cata- lysts. A correlation between the BDE of R-X and dispersion efficiency was established. The tendency for disintegration and redispersion followed the R-X BDE of the alkyl halide. Compared to alkyl chlorides and bromides, iodides were more efficient for redispersing sintered Au NPs. As a descriptor, the BDE of R-I played a crucial role in particle redispersion. These findings provided in- sights into the mechanism of organic halide-induced Au NP disintegration and the effect of the hal- ide type on the redispersion of sintered catalysts.
基金supported by the National Natural Science Foundation of China(201573136,U1510105)the Scientific Research Start-up Funds of Shanxi University(RSC723)~~
文摘Due to the advantages of high surface areas, large pore volumes and pore sizes, abundant nitrogen content that favored the metal-support interactions, N-doped ordered mesoporous carbons are regarded as a kind of fascinating and potential support for the synthesis of effective supported cat-alysts. Here, a N-doped ordered mesoporous carbon with a high N content （9.58 wt%）, high surface area （417 m^2/g）, and three-dimensional cubic structure was synthesized successfully and used as an effective support for immobilizing Pt nanoparticles （NPs）. The positive effects of nitrogen on the metal particle size enabled ultrasmall Pt NPs （about 1.0 ± 0.5 nm） to be obtained. Moreover, most of the Pt NPs are homogeneously dispersed in the mesoporous channels. However, using the ordered mesoporous carbon without nitrogen as support, the particles were larger （4.4 ± 1.7 nm） and many Pt NPs were distributed on the external surface, demonstrating the important role of the nitrogen species. The obtained N-doped ordered mesoporous material supported catalyst showed excellent catalytic activity （conversion 100%） and selectivity （〉99%） in the hydrogenation of halogenated nitrobenzenes under mild conditions. These values are much higher than those achieved using a commercial Pt/C catalyst （conversion 89% and selectivity 90%）. This outstanding catalytic perfor-mance can be attributed to the synergetic effects of the mesoporous structure, N-functionalized support, and stabilized ultrasmall Pt NPs. Moreover, such supported catalyst also showed excellent catalytic performance in the hydrogenation of other halogenated nitrobenzenes and nitroarenes. In addition, the stability of the multifunctional catalyst was excellent and it could be reused more than 10 times without significant losses of activity and selectivity. Our results conclusively show that a N-doped carbon support enable the formation of ultrafine metal NPs and improve the reaction ac-tivity and selectivity.
文摘A straightforward protocol using readily available aromatic amines,N,N,N',N'-tetramethyl-p-phenylenediamine or N,N,N',N'-tetramethylbenzidine,as photocatalysts was developed for theefficient hydrodehalogenation of organic halides,such as 4'-bromoacetophenone,polyfluoroarenes,cholorobenzene,and 2,2',4,4'-tetrabromodiphenyl ether(a resistant and persistent organic pollu-tant).The strongly reducing singlet excited states of the amines enabled diffusion-controlled disso-ciative electron transfer to effectively cleave carbon-halogen bonds,followed by radical hydrogena-tion.Diisopropylethylamine served as the terminal electron/proton donor and regenerated theamine sensitizers.
基金Supported by the National Natural Science Foundation of China(Nos.21473159 and91334013)
文摘The selective hydrogenation of halogenated nitrobenzene over noble metal catalysts(Pd, Pt, and Ir) has attracted much attention owing to its high efficiency and environmental friendliness. However, the effect of size on the catalytic performance varies among different metal catalysts. In this study, sub-nano(<3 nm) Ir and Pd particles were prepared, and their catalytic properties for hydrogenation of halogenated nitrobenzene were evaluated.Results show that high selectivity(N 99%) was achieved over small Ir nanoparticles, in which the selectivity over the Pd with same size was much lower than that on Ir nanoparticles. Meanwhile, Ir and Pd have different hydrogen consumption rates and reaction rates. Density functional theory calculations showed that p-chloronitrobenzene(CNB) has different adsorption properties on Ir and Pd. The distance between oxygen(cholorine) and Ir is much shorter(longer) than that between oxygen and Pd. The reaction barriers of dechlorination of p-CNB and p-chloroaniline over different Ir models are much larger than those on Pd. Especially,lower coordination of Ir leads to larger barriers of dechlorination reaction. These theoretical results explain the difference between Ir and Pd on hydrogenation of halogenated nitrobenzene.
基金supported by the National Natural Science Foundation of China(21972094,21902105)the National Postdoctoral Program for Innovative Talents(BX20180203)+4 种基金China Postdoctoral Science Foundation(2018M643176)Guangdong Special Support ProgramPengcheng Scholar programShenzhen Peacock Plan(KQJSCX20170727100802505 and KQTD2016053112042971)Foundation for Distinguished Young Talents in Higher Education of Guangdong(2018KQNCX221)。
文摘Tandem water electrolysis for the transformation of universal feedstock to value-added chemicals integrated with hydrogen generation and in situ utilization is a promising approach to address the economic challenges of electrochemical hydrogen evolution and storage.Herein,we present the controllable electrocatalytic deuteration of halides using inexpensive and reusable heavy water(D2 O)as a D-source for the preparation of valuable D-labelled chemicals and pharmaceuticals under mild conditions.This electrochemical deuteration method with high efficiency and selectivity furnishes a series of D-labelled chemicals and pharmaceuticals in high yields with excellent D-incorporation.The reaction efficiency and selectivity,that is,the precise substitution of deuterium atoms at different halogen positions,can be tuned by varying the applied voltages.The results show the great potential of green and economical electrocatalytic methods for producing value-added fine chemicals in addition to hydrogen evolution.
