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
Plasmonic Pd nanosheets have been emerging as promising materials for application in near-infrared(NIR) photothermal therapy(PTT) of cancer. However, animal in mice studies indicated that the original synthesized poly...Plasmonic Pd nanosheets have been emerging as promising materials for application in near-infrared(NIR) photothermal therapy(PTT) of cancer. However, animal in mice studies indicated that the original synthesized poly(vinylpyrrolidone)(PVP)-protected small Pd nanosheets(Pd-PVP) and some further surface-modified small Pd nanosheets such as Pd-PEG(SH) easily accumulated in reticuloendothelial system(RES) organs(liver, spleen, etc.) and were difficult to be cleared from these organs quickly. In the work, we surprisingly found that glutathione(GSH) could promote the clearance of surface-modified small Pd nanosheets(e.g. Pd-PVP, Pd-PEG(SH) and Pd-GSH) from the RES organs efficiently. The effects of GSH on the biodistribution and clearance of different surface-modified Pd nanosheets were investigated. Our results indicated that these surface-modified Pd nanosheets with or without GSH added caused no morbidity at target primary organs, and GSH can promote the clearance of different surface-modified Pd nanosheets in the order of Pd-PVP≈Pd-PEG(SH)>Pd-GSH. This study suggests that glutathione could be an attractive reagent for promoting nanomaterials eliminated from the reticuloendothelial systems(RES).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
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
Two-dimensional (2D) nanosheets have emerged as an important class of nanomaterial with great potential in the field of biomedicines, particularly in cancer theranostics. However, owing to the lack of effective meth...Two-dimensional (2D) nanosheets have emerged as an important class of nanomaterial with great potential in the field of biomedicines, particularly in cancer theranostics. However, owing to the lack of effective methods that synthesize uniform 2D nanomaterials with controlled size, systematic evaluation of size-dependent bio-behaviors of 2D nanomaterials is rarely reported. To the best of our knowledge, we are the first to report a systematic evaluation of the influence of size of 2D nanomaterials on their bio-behaviors. 2D Pd nanosheets with diameters ranging from 5 to 80 nm were synthesized and tested in cell and animal models to assess their size-dependent bioapplication, biodistribution, elimination, toxicity, and genomic gene expression profiles. Our results showed size significantly influences the biological behaviors of Pd nanosheets, including their photothermal and photoacoustic effects, pharmacokinetics, and toxicity. Compared to larger-sized Pd nanosheets, smaller-sized Pd nanosheets exhibited more advanced photoacoustic imaging and photothermal effects upon ultralow laser irradiation. Moreover, in vivo results indicated that 5-nm Pd nanosheets escape from the reticuloendothelial system with a longer blood half-life and can be cleared by renal excretion, while Pd nanosheets with larger sizes mainly accumulate in the liver and spleen. The 30-nm Pd nanosheets exhibited the highest tumor accumulation. Although Pd nanosheets did not cause any appreciable toxicity at the cellular level, we observed slight lipid accumulation in the liver and inflammation in the spleen. Genomic gene expression analysis showed that 80-nm Pd nanosheets interacted with more cellular components and affected more biological processes in the liver, as compared to 5-nm Pd nanosheets. We believe this work will provide valuable information and insights into the clinical application of 2D Pd nanosheets as nanomedicines.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supported by the National Natural Science Foundation of China(21101131)the National Basic Research Program of China(2014CB932004)+2 种基金the Natural Science Foundation of Fujian Province(2012J01056)the Fundamental Research Funds for the Central Universities(2010121015)the open project grant from State Key Laboratory of Chemo/biosensing and Chemometrics(2013009)
文摘Plasmonic Pd nanosheets have been emerging as promising materials for application in near-infrared(NIR) photothermal therapy(PTT) of cancer. However, animal in mice studies indicated that the original synthesized poly(vinylpyrrolidone)(PVP)-protected small Pd nanosheets(Pd-PVP) and some further surface-modified small Pd nanosheets such as Pd-PEG(SH) easily accumulated in reticuloendothelial system(RES) organs(liver, spleen, etc.) and were difficult to be cleared from these organs quickly. In the work, we surprisingly found that glutathione(GSH) could promote the clearance of surface-modified small Pd nanosheets(e.g. Pd-PVP, Pd-PEG(SH) and Pd-GSH) from the RES organs efficiently. The effects of GSH on the biodistribution and clearance of different surface-modified Pd nanosheets were investigated. Our results indicated that these surface-modified Pd nanosheets with or without GSH added caused no morbidity at target primary organs, and GSH can promote the clearance of different surface-modified Pd nanosheets in the order of Pd-PVP≈Pd-PEG(SH)>Pd-GSH. This study suggests that glutathione could be an attractive reagent for promoting nanomaterials eliminated from the reticuloendothelial systems(RES).
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.
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Acknowledgements This work was supported by the National Basic Research Program of China (Nos. 2014CB932004 and 2015CB932303) and the National Natural Science Foundation of China (Nos. 21420102001, 21131005 and 81422023).
文摘Two-dimensional (2D) nanosheets have emerged as an important class of nanomaterial with great potential in the field of biomedicines, particularly in cancer theranostics. However, owing to the lack of effective methods that synthesize uniform 2D nanomaterials with controlled size, systematic evaluation of size-dependent bio-behaviors of 2D nanomaterials is rarely reported. To the best of our knowledge, we are the first to report a systematic evaluation of the influence of size of 2D nanomaterials on their bio-behaviors. 2D Pd nanosheets with diameters ranging from 5 to 80 nm were synthesized and tested in cell and animal models to assess their size-dependent bioapplication, biodistribution, elimination, toxicity, and genomic gene expression profiles. Our results showed size significantly influences the biological behaviors of Pd nanosheets, including their photothermal and photoacoustic effects, pharmacokinetics, and toxicity. Compared to larger-sized Pd nanosheets, smaller-sized Pd nanosheets exhibited more advanced photoacoustic imaging and photothermal effects upon ultralow laser irradiation. Moreover, in vivo results indicated that 5-nm Pd nanosheets escape from the reticuloendothelial system with a longer blood half-life and can be cleared by renal excretion, while Pd nanosheets with larger sizes mainly accumulate in the liver and spleen. The 30-nm Pd nanosheets exhibited the highest tumor accumulation. Although Pd nanosheets did not cause any appreciable toxicity at the cellular level, we observed slight lipid accumulation in the liver and inflammation in the spleen. Genomic gene expression analysis showed that 80-nm Pd nanosheets interacted with more cellular components and affected more biological processes in the liver, as compared to 5-nm Pd nanosheets. We believe this work will provide valuable information and insights into the clinical application of 2D Pd nanosheets as nanomedicines.
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.