The determination of catalytically active sites is crucial for the design of efficient and stable catalysts toward desired reactions.However,the complexity of supported noble metal catalysts has led to controversy ove...The determination of catalytically active sites is crucial for the design of efficient and stable catalysts toward desired reactions.However,the complexity of supported noble metal catalysts has led to controversy over the locations of catalytically active sites(e.g.,metal,support,and metal/support interface).Here we develop a structurally controllable catalyst system(Pd/SBA-15)to reveal the catalytic active sites for the selective hydrogenation of ketones to alcohol using acetophenone hydrogenation as model reaction.Systematic investigations demonstrated that unsupported Pd nanocrystals have no catalytic activity for acetophenone hydrogenation.However,oxidized Pd species were catalytically highly active for acetophenone hydrogenation.The catalytic activity decreased with the decreased oxidation state of Pd.This work provides insights into the hydrogenation mechanism of ketones but also other unsaturated compounds containing polar bonds,e.g.,nitrobenzene,N-benzylidene-benzylamine,and carbon dioxide.展开更多
Atomically dispersed catalysts have demonstrated superior catalytic performance in many chemical transformations.However,limited success has been achieved in applying oxide-supported atomically dis-persed catalysts to...Atomically dispersed catalysts have demonstrated superior catalytic performance in many chemical transformations.However,limited success has been achieved in applying oxide-supported atomically dis-persed catalysts to semihydrogenation of alkynes under mild conditions.展开更多
While the enzymatic reduction of unsaturated compounds usually has high specificity,highly selective reduction processes are hardly realized by heterogeneous industrial catalysts,which is critical for the green produc...While the enzymatic reduction of unsaturated compounds usually has high specificity,highly selective reduction processes are hardly realized by heterogeneous industrial catalysts,which is critical for the green production of many fine chemicals.Here,we report an unexpected discovery of a biomimetic behavior of dicyandiamide(DICY)-modified Pt nanocatalysts for the green hydrogenation of a wide range of nitroaromatics.We demonstrate that the surface modification by DICY not only prevents the direct contact of nitroaromatic reactants with Pt surface but also induces an effective non-contact hydrogenation mechanism mediated by protons and electrons.In such a process,the DICY layer serves as a“semi-permeable membrane”to allow the permeation of H_(2) molecules for being activated into electrons and protons at the Pt-DICY interface.With the generation of separated protons and electrons,the nitro group with strong electrophilic properties can be hydrogenated through the electron transfer followed by the proton transfer,which is facilitated by the hydrogen bonding network formed by protonated DICY.The unique mechanism makes it highly directional toward the hydrogenation of nitro groups without side reactions.Owing to its capability to largely eliminate the waste generation,the developed Pt-DICY catalysts have been successfully applied for the green industrial production of many important aniline intermediates.展开更多
基金supported by the National Natural Science Foundation of China(Nos.92261207,21890752,and 22002126)。
文摘The determination of catalytically active sites is crucial for the design of efficient and stable catalysts toward desired reactions.However,the complexity of supported noble metal catalysts has led to controversy over the locations of catalytically active sites(e.g.,metal,support,and metal/support interface).Here we develop a structurally controllable catalyst system(Pd/SBA-15)to reveal the catalytic active sites for the selective hydrogenation of ketones to alcohol using acetophenone hydrogenation as model reaction.Systematic investigations demonstrated that unsupported Pd nanocrystals have no catalytic activity for acetophenone hydrogenation.However,oxidized Pd species were catalytically highly active for acetophenone hydrogenation.The catalytic activity decreased with the decreased oxidation state of Pd.This work provides insights into the hydrogenation mechanism of ketones but also other unsaturated compounds containing polar bonds,e.g.,nitrobenzene,N-benzylidene-benzylamine,and carbon dioxide.
基金This work was supported by the National Key Research and Development Program of China(2017YFA0207302 and 2017YFA0207303)the National Natural Science Foundation of China(21890752,21731005,21420102001,21573178,and 91845102)the Fundamental Research Funds for Central Universities(20720180026).
文摘Atomically dispersed catalysts have demonstrated superior catalytic performance in many chemical transformations.However,limited success has been achieved in applying oxide-supported atomically dis-persed catalysts to semihydrogenation of alkynes under mild conditions.
基金supported by the National Key Research and Development Program of China(2017YFA0207302)the National Nature Science Foundation of China(21890752,21731005,22072116,92045303)+1 种基金support from the Tencent Foundation through the XPLORER PRIZEthe XAFS Station(BL14W1)of the Shanghai Synchrotron Radiation Facility(SSRF)。
文摘While the enzymatic reduction of unsaturated compounds usually has high specificity,highly selective reduction processes are hardly realized by heterogeneous industrial catalysts,which is critical for the green production of many fine chemicals.Here,we report an unexpected discovery of a biomimetic behavior of dicyandiamide(DICY)-modified Pt nanocatalysts for the green hydrogenation of a wide range of nitroaromatics.We demonstrate that the surface modification by DICY not only prevents the direct contact of nitroaromatic reactants with Pt surface but also induces an effective non-contact hydrogenation mechanism mediated by protons and electrons.In such a process,the DICY layer serves as a“semi-permeable membrane”to allow the permeation of H_(2) molecules for being activated into electrons and protons at the Pt-DICY interface.With the generation of separated protons and electrons,the nitro group with strong electrophilic properties can be hydrogenated through the electron transfer followed by the proton transfer,which is facilitated by the hydrogen bonding network formed by protonated DICY.The unique mechanism makes it highly directional toward the hydrogenation of nitro groups without side reactions.Owing to its capability to largely eliminate the waste generation,the developed Pt-DICY catalysts have been successfully applied for the green industrial production of many important aniline intermediates.
