A new approach to allylic alkylation is realized using an atomically dispersed palladium catalyst(Pd1/TiO2-EG).Unlike conventional methods that require derivation of substrates and utilization of additives,this method...A new approach to allylic alkylation is realized using an atomically dispersed palladium catalyst(Pd1/TiO2-EG).Unlike conventional methods that require derivation of substrates and utilization of additives,this method allows for direct allylic alkylation from allylic alcohols,producing H2O as the sole by-product.The catalyst's high efficiency is attributed to the local hydrogen bonding at the or-ganic-inorganic interface(Pd-EG interface),facilitating hydroxyl group activation forη3π-allyl complex formation.The system demonstrates successful direct C—O and C—C coupling reactions with high selectivity,requiring no additives.This study highlights the potential of supported atomically dispersed catalysts for greener and more efficient catalysis,meanwhile,offers unique insights into the distinct behavior of atomically dispersed catalysts in comparison to homogeneous or nanoparticle-based catalysts.展开更多
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
Supported metal catalysts integrating advantages of catalytic hydrogenation and stoichiometric reduction are highly desirable for the green production of fine chemicals.Decoupling catalytic hydrogenation into H_(2)act...Supported metal catalysts integrating advantages of catalytic hydrogenation and stoichiometric reduction are highly desirable for the green production of fine chemicals.Decoupling catalytic hydrogenation into H_(2)activation and selective reduction taking place at different locations is expected to provide an effective strategy to fabricate such catalyst systems.Herein,we report a decoupled hydrogenation system by modifying Pt catalysts supported on reducible In2O3 with ethylenediamine(EDA).The system exhibits good catalytic performance in oximes production from nitroalkanes,an industrially important reaction,by employing H_(2).Systematic studies demonstrate that the surface coordination of EDA on Pt is crucial to passivate the Pt surface from nitro hydrogenation without inhibiting H_(2)activation.The activated H_(2)species can then transfer and reduce the In_(2)O_(3)support in situ to generate sustainable stoichiometric reducing agents for the chemoselective reduction of nitroalkanes.Based upon the mechanistic understanding,a sustainable strategy for the production of oximes has been successfully fabricated.展开更多
Atomically dispersing metal atoms on supports has been emerging as an effective strategy to maximize the atom utilization of metals for catalysis. However, due to the lack of effective tools to characterize the detail...Atomically dispersing metal atoms on supports has been emerging as an effective strategy to maximize the atom utilization of metals for catalysis. However, due to the lack of effective tools to characterize the detailed structure of metal-support interface, the chemical functions of supports in atomically dispersed metal catalysts are hardly elucidated at the molecular level. In this work, an atomically dispersed Pd_1/TiO_2 catalyst with Ti(Ⅲ) vicinal to Pd is prepared and used to demonstrate the direct involvement of metal atoms on support in the catalysis of dispersed metal atoms. Systematic studies reveal that the Ti(Ⅲ)-O-Pd interface facilitates the activation of O_2 into superoxide(O_2^-), thus promoting the catalytic oxidation. The catalyst exhibits the highest CO turn-over frequency among ever-reported Pd-based catalysts,and enhanced catalysis in the combustion of harmful volatile organic compound(i.e., toluene) and greenhouse gas(i.e., methane). The demonstrated direct involvement of metal atoms on oxide support suggests that the real active sites of atomically dispersed metal catalysts can be far beyond isolated metal atoms themselves. Metal atoms on oxide supports in the vicinity serve as another vector to promote the catalysis of atomically dispersed metal catalysts.展开更多
Attaining high activity with high selectivity at low temperature is challenging in the selective hydrogenation of phenol to cyclohexanone due to its high activation energy(E_a, 55–70 kJ/mol). Here we report a simple ...Attaining high activity with high selectivity at low temperature is challenging in the selective hydrogenation of phenol to cyclohexanone due to its high activation energy(E_a, 55–70 kJ/mol). Here we report a simple and efficient strategy for phenol hydrogenation catalyzed by Pd in aqueous phase at 30 °C by introducing air to promote the catalysis. With the assistance of air, >99% conversion and >99% selectivity were achieved over Pd(111)/Al_2O_3 with an overall turnover frequency(TOF) of621 h^(-1), ~80 times greater than that of the state-of-art Pd catalyst at 30 °C. Mechanism studies revealed that phenol was activated to generate phenoxyl radicals. The radicals were yielded from the reaction between phenol and hydroxyl radicals in the presence of hydrogen, oxygen and protic solvent on Pd. The phenoxyl pathway resulted in a low apparent E_a(8.2 kJ/mol) and thus high activity. More importantly, this strategy of activating substrate by air can be adapted to other Pd based catalysts, offering a new thinking for the rational design of cyclohexanone production in industry.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
A facile one-pot synthetic strategy is developed to prepare high-quality Pt supercubes. The as-synthesized Pt supercubes are composed of the uniform Pt nanocubes arranged in a primitive cubic structure. The shape and ...A facile one-pot synthetic strategy is developed to prepare high-quality Pt supercubes. The as-synthesized Pt supercubes are composed of the uniform Pt nanocubes arranged in a primitive cubic structure. The shape and size of the Pt superparticles are readily tuned by varying the structures of pyridyl-containing ligands used in the synthesis. The co-presence of CO and nitrogen-containing ligands is critical to the formation of Pt supercubes. While CO molecules play an important role in the synthesis of Pt nanocube, introducing nitrogen-containing ligands is essential to the successful assembly of those nanocubes into Pt supercubes. Our systematic studies reveal that the electrostatic attraction between positively charged ligands and negatively charged Pt nanocubes is the main driving force for the assembly of Pt nanocubes into supercubes. More importantly, the ligands within the Pt supercubes are readily removed at relatively low temperature to yield surface-clean supercubes which are expected to exhibit unique size-selective catalysis.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
Size effect plays a crucial role in catalytic hydrogenation.The highly dispersed ultrasmall clusters with a limited number of metal atoms are one candidate of the next generation catalysts that bridge the single-atom ...Size effect plays a crucial role in catalytic hydrogenation.The highly dispersed ultrasmall clusters with a limited number of metal atoms are one candidate of the next generation catalysts that bridge the single-atom metal catalysts and metal nanoparticles.However,for the unfavorable electronic property and their interaction with the substrates,they usually exhibit sluggish activity.Taking advantage of the small size,their catalytic property would be mediated by surface binding species.The combination of metal cluster coordination chemistry brings new opportunity.CO poisoning is notorious for Pt group metal catalysts as the strong adsorption of CO would block the active centers.In this work,we will demonstrate that CO could serve as a promoter for the catalytic hydrogenation when ultrasmall Pd clusters are employed.By means of DFT calculations,we show that Pd_(n)(n=2-147)clusters display sluggish activity for hydrogenation due to the too strong binding of hydrogen atom and reaction intermediates thereon,whereas introducing CO would reduce the binding energies of vicinal sites,thus enhancing the hydrogenation reaction.Experimentally,supported Pd_(2)CO catalysts are fabricated by depositing preestablished[Pd_(2)(μ-CO)_(2)Cl_(4)]2-clusters on oxides and demonstrated as an outstanding catalyst for the hydrogenation of styrene.The promoting effect of CO is further verified experimentally by removing and reintroducing a proper amount of CO on the Pd cluster catalysts.展开更多
基金support from National Key R&D Program of China (2022YFA1504500)the National Natural Science Foundation of China (grant no.92261207,and NSFC Center for Single-Atom Catalysis under grant no.22388102)+4 种基金the New Cornerstone Science Foundation.P.L.acknowledges the Shanghai Pujiang Talent Program (No.21PJ1410400)the Start-up Funding and the Double First-Class Initiative Fund of ShanghaiTech University.R.Q.acknowledges support from the Young Scientists Fund of the National Natural Science Foundation of China (22202164)the Natural Science Foundation of Fujian Province (2023J05006)the Fundamental Research Funds for the Central Universities (20720230002)the Fujian Provincial Chemistry Discipline Alliance.
文摘A new approach to allylic alkylation is realized using an atomically dispersed palladium catalyst(Pd1/TiO2-EG).Unlike conventional methods that require derivation of substrates and utilization of additives,this method allows for direct allylic alkylation from allylic alcohols,producing H2O as the sole by-product.The catalyst's high efficiency is attributed to the local hydrogen bonding at the or-ganic-inorganic interface(Pd-EG interface),facilitating hydroxyl group activation forη3π-allyl complex formation.The system demonstrates successful direct C—O and C—C coupling reactions with high selectivity,requiring no additives.This study highlights the potential of supported atomically dispersed catalysts for greener and more efficient catalysis,meanwhile,offers unique insights into the distinct behavior of atomically dispersed catalysts in comparison to homogeneous or nanoparticle-based catalysts.
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supported by the National Key R&D Program of China(2017YFA0207302)the National Natural Science Foundation of China(21890752,21731005,21573178,21773192,and 91845102)+3 种基金the Tencent Foundation through the XPLORER PRIZEChina Postdoctoral Science Foundation Project(2021T140394 and 2021M691877)the Young Scientists Fund of the National Natural Science Foundation of China(22202164).the funding from the Chemistry and Chemical Engineering Guangdong Laboratory(2211002 and 2111005)。
基金supported by the National Key R&D Program of China(grant no.2017YFA0207302)the National Natural Science Foundation of China(grant nos.21890752,21731005,21721001).
文摘Supported metal catalysts integrating advantages of catalytic hydrogenation and stoichiometric reduction are highly desirable for the green production of fine chemicals.Decoupling catalytic hydrogenation into H_(2)activation and selective reduction taking place at different locations is expected to provide an effective strategy to fabricate such catalyst systems.Herein,we report a decoupled hydrogenation system by modifying Pt catalysts supported on reducible In2O3 with ethylenediamine(EDA).The system exhibits good catalytic performance in oximes production from nitroalkanes,an industrially important reaction,by employing H_(2).Systematic studies demonstrate that the surface coordination of EDA on Pt is crucial to passivate the Pt surface from nitro hydrogenation without inhibiting H_(2)activation.The activated H_(2)species can then transfer and reduce the In_(2)O_(3)support in situ to generate sustainable stoichiometric reducing agents for the chemoselective reduction of nitroalkanes.Based upon the mechanistic understanding,a sustainable strategy for the production of oximes has been successfully fabricated.
基金supported by the National Key Research and Development Program of China(2017YFA0207302)the National Natural Science Foundation of China(21731005,21420102001,21373167,and 21573178)+1 种基金the National Postdoctoral Program for Innovative Talents(BX201600093)the China Postdoctoral Science Foundation Project(2017M610392)
文摘Atomically dispersing metal atoms on supports has been emerging as an effective strategy to maximize the atom utilization of metals for catalysis. However, due to the lack of effective tools to characterize the detailed structure of metal-support interface, the chemical functions of supports in atomically dispersed metal catalysts are hardly elucidated at the molecular level. In this work, an atomically dispersed Pd_1/TiO_2 catalyst with Ti(Ⅲ) vicinal to Pd is prepared and used to demonstrate the direct involvement of metal atoms on support in the catalysis of dispersed metal atoms. Systematic studies reveal that the Ti(Ⅲ)-O-Pd interface facilitates the activation of O_2 into superoxide(O_2^-), thus promoting the catalytic oxidation. The catalyst exhibits the highest CO turn-over frequency among ever-reported Pd-based catalysts,and enhanced catalysis in the combustion of harmful volatile organic compound(i.e., toluene) and greenhouse gas(i.e., methane). The demonstrated direct involvement of metal atoms on oxide support suggests that the real active sites of atomically dispersed metal catalysts can be far beyond isolated metal atoms themselves. Metal atoms on oxide supports in the vicinity serve as another vector to promote the catalysis of atomically dispersed metal catalysts.
基金supported by the Ministry of Science and Technology of China(2017YFA0207302,2015CB93230)the National Natural Science Foundation of China(21420102001,21333008)
文摘Attaining high activity with high selectivity at low temperature is challenging in the selective hydrogenation of phenol to cyclohexanone due to its high activation energy(E_a, 55–70 kJ/mol). Here we report a simple and efficient strategy for phenol hydrogenation catalyzed by Pd in aqueous phase at 30 °C by introducing air to promote the catalysis. With the assistance of air, >99% conversion and >99% selectivity were achieved over Pd(111)/Al_2O_3 with an overall turnover frequency(TOF) of621 h^(-1), ~80 times greater than that of the state-of-art Pd catalyst at 30 °C. Mechanism studies revealed that phenol was activated to generate phenoxyl radicals. The radicals were yielded from the reaction between phenol and hydroxyl radicals in the presence of hydrogen, oxygen and protic solvent on Pd. The phenoxyl pathway resulted in a low apparent E_a(8.2 kJ/mol) and thus high activity. More importantly, this strategy of activating substrate by air can be adapted to other Pd based catalysts, offering a new thinking for the rational design of cyclohexanone production in industry.
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 Basic Research Program of China(2011CB932403,2015CB932300)the National Natural Science Foundation of China(21420102001,21131005,21390390,21333008)
文摘A facile one-pot synthetic strategy is developed to prepare high-quality Pt supercubes. The as-synthesized Pt supercubes are composed of the uniform Pt nanocubes arranged in a primitive cubic structure. The shape and size of the Pt superparticles are readily tuned by varying the structures of pyridyl-containing ligands used in the synthesis. The co-presence of CO and nitrogen-containing ligands is critical to the formation of Pt supercubes. While CO molecules play an important role in the synthesis of Pt nanocube, introducing nitrogen-containing ligands is essential to the successful assembly of those nanocubes into Pt supercubes. Our systematic studies reveal that the electrostatic attraction between positively charged ligands and negatively charged Pt nanocubes is the main driving force for the assembly of Pt nanocubes into supercubes. More importantly, the ligands within the Pt supercubes are readily removed at relatively low temperature to yield surface-clean supercubes which are expected to exhibit unique size-selective catalysis.
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.
基金the National Key R&D Program of China(2017YFA0207304 and 2017YFA0207303)the NNSF of China(21890752,21731005,21721001,21573178,and 91845102)the Fundamental Research Funds for the Central Universities(20720180026)for financial support。
文摘Size effect plays a crucial role in catalytic hydrogenation.The highly dispersed ultrasmall clusters with a limited number of metal atoms are one candidate of the next generation catalysts that bridge the single-atom metal catalysts and metal nanoparticles.However,for the unfavorable electronic property and their interaction with the substrates,they usually exhibit sluggish activity.Taking advantage of the small size,their catalytic property would be mediated by surface binding species.The combination of metal cluster coordination chemistry brings new opportunity.CO poisoning is notorious for Pt group metal catalysts as the strong adsorption of CO would block the active centers.In this work,we will demonstrate that CO could serve as a promoter for the catalytic hydrogenation when ultrasmall Pd clusters are employed.By means of DFT calculations,we show that Pd_(n)(n=2-147)clusters display sluggish activity for hydrogenation due to the too strong binding of hydrogen atom and reaction intermediates thereon,whereas introducing CO would reduce the binding energies of vicinal sites,thus enhancing the hydrogenation reaction.Experimentally,supported Pd_(2)CO catalysts are fabricated by depositing preestablished[Pd_(2)(μ-CO)_(2)Cl_(4)]2-clusters on oxides and demonstrated as an outstanding catalyst for the hydrogenation of styrene.The promoting effect of CO is further verified experimentally by removing and reintroducing a proper amount of CO on the Pd cluster catalysts.