The aim of ＂green chemistry＂ and ＂atom economy＂ is to utilize carbon dioxide and replace harmful reactants such as CO and phosgene for the production of cyclic carbonates. In this paper, metal-free catalysts inclu...The aim of ＂green chemistry＂ and ＂atom economy＂ is to utilize carbon dioxide and replace harmful reactants such as CO and phosgene for the production of cyclic carbonates. In this paper, metal-free catalysts including organic bases, ionic liquids, supported catalysts, organic copolymers and carbon materials for the synthesis of cyclic carbonates by the cycloaddition of carbon dioxide to epoxides are reviewed. Recent advances in the design of the catalysts and the understanding of the reaction mechanism are summarized and discussed. The synergistic effects of organic bases and hydrogen bond donors, organic bases and nucleophilic anions, hydrogen bond donors and nucleophilic anions and active components and supports are highlighted. The challenge is to develop metal-free catalysts suitable for carbon dioxide capture and fixation. The ultimate goal is to synthesize cyclic carbonates in a flow reactor directly using carbon dioxide from industrial flue gas at ambient temperature and atmospheric pressure. By using synergetic effects, a multi-functional approach can meet the design strategy of metal-free catalysts for carbon dioxide adsorption and activation as well as epoxide ring opening.展开更多
The greenhouse effect and global warming are serious problems because the increasing global demand for fossil fuels has led to a rapid rise in greenhouse gas exhaust emissions in the atmosphere and disruptive changes ...The greenhouse effect and global warming are serious problems because the increasing global demand for fossil fuels has led to a rapid rise in greenhouse gas exhaust emissions in the atmosphere and disruptive changes in climate. As a major contributor, CO2 has attracted much attention from scientists, who have attempted to convert it into useful products by electrochemical or photoelectrochemical reduction methods. Facile design of efficient but inexpensive and abundant catalysts to convert CO2 into fuels or valuable chemical products is essential for materials chemistry and catalysis in addressing global climate change as well as the energy crisis. Herein, we show that two-dimensional fewlayer graphitic carbon nitride （g-C3N4） can function as an efficient metal-free electrocatalyst for selective reduction of CO2 to CO at low overpotentials with a high Faradaic efficiency of - 80%. The polarized surface of ultrathin g-C3N4 layers （thickness： -1 nm）, with a more reductive conduction band, yields excellent electrochemical activity for CO2 reduction.展开更多
Electrochemical CO2 reduction to chemicals or fuels presents one of the most promising strategies for managing the global carbon balance, which yet poses a significant challenge due to lack of efficient and durable el...Electrochemical CO2 reduction to chemicals or fuels presents one of the most promising strategies for managing the global carbon balance, which yet poses a significant challenge due to lack of efficient and durable electrocatalyst as well as the understanding of the CO2 reduction reaction(CO2RR) mechanism.Benefiting from the large surface area, high electrical conductivity, and tunable structure, carbon-based metal-free materials(CMs) have been extensively studied as cost-effective electrocatalysts for CO2RR.The development of CMs with low cost, high activity and durability for CO2RR has been considered as one of the most active and competitive directions in electrochemistry and material science.In this review article,some up-to-date strategies in improving the CO2RR performance on CMs are summarized.Specifically, the approaches to optimize the adsorption of CO2RR intermediates, such as tuning the physical and electronic structure are introduced, which can enhance the electrocatalytic activity of CMs effectively.Finally, some design strategies are proposed to prepare CMs with high activity and selectivity for CO2RR.展开更多
Covalent organic frameworks(COFs)have emerged as a kind of rising star materials in photocatalysis.However,their photocatalytic activities are restricted by the high photogenerated electron-hole pairs recombination ra...Covalent organic frameworks(COFs)have emerged as a kind of rising star materials in photocatalysis.However,their photocatalytic activities are restricted by the high photogenerated electron-hole pairs recombination rate.Herein,a novel metal-free 2D/2D van der Waals heterojunction,composed of a two-dimensional(2D)COF with ketoenamine linkage(TpPa-1-COF)and 2D defective hexagonal boron nitride(h-BN),is successfully constructed through in situ solvothermal method.Benefitting from the presence of VDW heterojunction,larger contact area and intimate electronic coupling can be formed between the interface of TpPa-1-COF and defective h-BN,which make contributions to promoting charge car-riers separation.The introduced defects can also endow the h-BN with porous structure,thus providing more reactive sites.Moreover,the TpPa-1-COF will undergo a structural transformation after being integrated with defective h-BN,which can enlarge the gap between the conduction band position of the h-BN and TpPa-1-COF,and suppress electron backflow,corroborated by experimental and density functional theory calculations results.Accordingly,the resulting porous h-BN/TpPa-1-COF metal-free VDW heterojunction displays out-standing solar energy catalytic activity for water splitting without co-catalysts,and the H_(2) evolution rate can reach up to 3.15 mmol g^(−1) h^(−1),which is about 67 times greater than that of pristine TpPa-1-COF,also surpassing that of state-of-the-art metal-free-based photocatalysts reported to date.In particular,it is the first work for constructing COFs-based heterojunctions with the help of h-BN,which may provide new avenue for designing highly efficient metal-free-based photocatalysts for H_(2) evolution.展开更多
Since the discovery of the first carbon-based metal-free electrocatalysts(C-MFECs,i.e.,N-doped carbon nanotubes)for the oxygen reduction reaction in 2009,the field of C-MFECs has grown enormously over the last 10 year...Since the discovery of the first carbon-based metal-free electrocatalysts(C-MFECs,i.e.,N-doped carbon nanotubes)for the oxygen reduction reaction in 2009,the field of C-MFECs has grown enormously over the last 10 years.C-MFECs,as alternatives to nonprecious transition metals and/or precious noble metal-based electrocatalysts,have been consistently demonstrated as efficient catalysts for oxygen reduction,oxygen evolution,hydrogen evolution,carbon dioxide reduction,nitrogen reduction,and many other(electro-)chemical reactions.Recent research and development of C-MFECs have indicated their potential applications in fuel cells,metal-air batteries,and hydrogen generation through water oxidation as well as electrochemical production of various commodity chemicals,such as ammonia,alcohols,hydrogen peroxide,and other useful hydrocarbons.Further research and development of C-MFECs would surely revolutionize traditional energy conversion and storage technologies with minimal environmental impact.In this short review article,we summarize the journey of C-MFECs over the past 10 years with an emphasis on materials development and their structure-property characterization for applications in fuel cells and metal-air batteries.Current challenges and future prospects of this emerging field are also discussed.展开更多
To date,much efforts have been devoted to the high-efficiency noble metal-free electrocatalysts for hydrogen-and oxygen-involving energy conversion reactions,due to their abundance,low cost and nultifunctionally.Surfa...To date,much efforts have been devoted to the high-efficiency noble metal-free electrocatalysts for hydrogen-and oxygen-involving energy conversion reactions,due to their abundance,low cost and nultifunctionally.Surface/interface engineering is found to be effective in achieving novel physicochemical properties and synergistic effects in nanomaterials for electrocatalysis.Among various engineering strategies,heteroatom-doping has been regarded as a most promising method to improve the electrocatalytic performance via the regulation of electronic structure of catalysts,and numerous works were reported on the synthesis method and mechanism investigation of heteroatom-doping electrocatalysts,though the heteroatom-doping can only provide limited active sites.Engineering of other defects such as vacancies and edge sites and construction of heterostructure have shown to open up a potential avenue for the development of noble metal-free electrocatalysts.In addition,surface functionalization can attach various molecules onto the surface of materials to easily modify their physical or chemical properties,being as a promising complement or substitute for offering materials with catalytic properties.This paper gives the insights into the diverse strategies of surface/interface engineering of the highefficiency noble metal-free electrocatalysts for energy-related electrochemical reactions.The significant advances are summarized.The unique advantages and mechanisms for specific applications are highlighted.The current challenges and outlook of this growing field are also discussed.展开更多
Nanocarbon materials have been used as important metal-free catalysts for various reactions including alkane dehydrogenation.However,clarifying the active sites and tuning the nanocarbon structure for direct dehydroge...Nanocarbon materials have been used as important metal-free catalysts for various reactions including alkane dehydrogenation.However,clarifying the active sites and tuning the nanocarbon structure for direct dehydrogenation have always been significantly challenging owing to the lack of fundamental understanding of the structure and surface properties of carbon materials.Herein,mesoporous carbon materials with different pore ordering and surface properties were synthesized through a soft-templating method with different formaldehyde/resorcinol ratios and carbonization temperatures and used for catalytic dehydrogenation of propane to propylene.The highly ordered mesoporous carbons were found to have higher catalytic activities than disordered and ordered mesoporous carbons,mainly because the highly ordered mesopores favor mass transportation and provide more accessible active sites.Furthermore,mesoporous carbons can provide a large amount of surface active sites owing to their high surface areas,which is favorable for propane dehydrogenation reaction.To control the surface oxygenated functional groups,highly ordered mesoporous carbons were carbonized at different temperatures(600,700,and 800℃).The propylene formation rates exhibit an excellent linear relationship with the number of ketonic C=O groups,suggesting that C=O groups are the most possible active sites.展开更多
Regioseletive 1,3-dipolar polycycloadditions of 4,4'-isopropylidenediphenyl dipropiolate (1) and tetraphenylethene (TPE)-containing diazides (2) are carried out in polar solvents such as DMF/toluene at a moderate ...Regioseletive 1,3-dipolar polycycloadditions of 4,4'-isopropylidenediphenyl dipropiolate (1) and tetraphenylethene (TPE)-containing diazides (2) are carried out in polar solvents such as DMF/toluene at a moderate temperature of 100℃ for 6 h,producing poly(aroxycarbonyltriazole)s (PACTs) P3 with high molecular weights (Mw up to 23900) and regioregularities (F1,4 up to ～90%) in high yields (up to ～99%).These metal-free click polymerizations can propagate smoothly in an open atmosphere without protection from oxygen and moisture.The obtained polymers are soluble in common organic solvents and thermally stable at temperatures up to 375℃.Thanks to their contained TPE moieties,the PACTs show aggregation-induced emission and can serve as fluorescent chemosensors for superamplified detection of explosives.展开更多
Ordered macroporous materials with rapid mass transport and enhanced active site accessibility are essential for achieving improved catalytic activity.In this study,boron phosphate crystals with a three-dimensionally ...Ordered macroporous materials with rapid mass transport and enhanced active site accessibility are essential for achieving improved catalytic activity.In this study,boron phosphate crystals with a three-dimensionally interconnected ordered macroporous structure and a robust framework were fabricated and used as stable and selective catalysts in the oxidative dehydrogenation(ODH)of propane.Due to the improved mass diffusion and higher number of exposed active sites in the ordered macroporous structure,the catalyst exhibited a remarkable olefin productivity of^16 golefin gcat^-1 h^-1,which is up to 2–100 times higher than that of ODH catalysts reported to date.The selectivity for olefins was 91.5%(propene:82.5%,ethene:9.0%)at 515℃,with a propane conversion of 14.3%.At the same time,the selectivity for the unwanted deep-oxidized CO2 product remained less than 1.0%.The tri-coordinated surface boron species were identified as the active catalytic sites for the ODH of propane.This study provides a route for preparing a new type of metal-free catalyst with stable structure against oxidation and remarkable catalytic activity,which may represent a potential candidate to promote the industrialization of the ODH process.展开更多
Room-temperature phosphorescence(RTP) has attracted much attention due to its potential applications in the fields of biological imaging, chemical sensors and so forth. Particularly, amorphous metal-free RTP materials...Room-temperature phosphorescence(RTP) has attracted much attention due to its potential applications in the fields of biological imaging, chemical sensors and so forth. Particularly, amorphous metal-free RTP materials show special advantages of low cost and good processability. In addition, non-conjugated polymers have seldom been reported as phosphorescent materials.In this work, a novel non-conjugated amorphous metal-free copolymer composed of brominated olefins and acrylamide was prepared in a facile way, which could engender blue-purple RTP emission. Polymers with different kinds of brominated olefins and different ratios of two monomers have been investigated with the purpose of researching the composition/property relationship that may affect the RTP properties. This unique phenomenon could be due to the clustering of carbonyl and amino units caused molecular interaction, and the heavy-atom effect enhanced intersystem crossing. Meantime, the hydrogen bonding in the system enhanced the conformation rigidification to reduce the non-radiative decay. This work provided a delicate way to construct non-conjugated metal-free RTP materials and supplied a new insight into the development of RTP materials.展开更多
The development of highly active and low-cost catalysts for electrochemical reactions is one of the most attractive topics in the renewable energy technology.Herein,the site-specific nitrogen doping of graphdiyne(GDY)...The development of highly active and low-cost catalysts for electrochemical reactions is one of the most attractive topics in the renewable energy technology.Herein,the site-specific nitrogen doping of graphdiyne(GDY)including grap-N,sp-N(Ⅰ)and sp-N(Ⅱ)GDY is systematically investigated as metal-free oxygen reduction electrocatalysts via density functional theory(DFT).Our results indicate that the doped nitrogen atom can significantly improve the oxygen(O2)adsorption activity of GDY through activating its neighboring carbon atoms.The free-energy landscape is employed to describe the electrochemical oxygen reduction reaction(ORR)in both O2 dissociation and association mechanisms.It is revealed that the association mechanism can provide higher ORR onset potential than dissociation mechanism on most of the substrates.Especially,sp-N(Ⅱ)GDY exhibits the highest ORR electrocatalytic activity through increasing the theoretical onset potential to 0.76 V.This work provides an atomic-level insight for the electrochemical ORR mechanism on metal-free N-doped GDY.展开更多
Electrocatalytic urea synthesis via coupling of nitrate with CO_(2)is considered as a promising alternative to the industrial urea synthetic process.However,the requirement of sub-reaction(NO_(3)RR and CO_(2)RR)activi...Electrocatalytic urea synthesis via coupling of nitrate with CO_(2)is considered as a promising alternative to the industrial urea synthetic process.However,the requirement of sub-reaction(NO_(3)RR and CO_(2)RR)activities for efficient urea synthesis is not clear and the related reaction mechanisms remain obscure.Here,the construction,breaking,and rebuilding of the sub-reaction activity balance would be accompanied by the corresponding regulation in urea synthesis,and the balance of sub-reaction activities was proven to play a vital role in efficient urea synthesis.With rational design,a urea yield rate of 610.6 mg h−1 gcat.−1 was realized on the N-doped carbon electrocatalyst,superior to that of noble-metal electrocatalysts.Based on the operando SRFTIR measurements,we proposed that urea synthesis arises from the coupling of^(*)NO and^(*)CO to generate the key intermediate of^(*)OCNO.This work provides new insights and guidelines into urea synthesis from the aspect of activity balance.展开更多
The electrochemical reduction of carbon dioxide(CO_(2))into value‐added fuels and chemicals presents a sustainable route to alleviate CO_(2) emissions,promote carbon‐neutral cycles and reduce the dependence on fossi...The electrochemical reduction of carbon dioxide(CO_(2))into value‐added fuels and chemicals presents a sustainable route to alleviate CO_(2) emissions,promote carbon‐neutral cycles and reduce the dependence on fossil fuels.Considering the thermodynamic stability of the CO_(2) molecule and sluggish reaction kinetics,it is still a challenge to design highly efficient electrocatalysts for the CO_(2) reduction reaction(CO_(2)RR).It has been found that the surface and interface chemistry of electrocatalysts can modulate the electronic structure and increase the active sites,which is favorable for CO_(2) adsorption,electron transfer,mass transport,and optimizing adsorption strength of reaction intermediates.However,the effect of surface and interface chemistry on metal‐free electrocatalysts(MFEs)for CO_(2)RR has not been comprehensively reviewed.Herein,we discuss the importance of the surface and interface chemistry on MFEs for improving the electrochemical CO_(2)RR performance based on thermodynamic and kinetic views.The fundamentals and challenges of CO_(2)RR are firstly presented.Then,the recent advances of the surface and interface chemistry in improving reaction rate and overcoming reaction constraints are reviewed from regulating electronic structure,active sites,electron transfer,mass transport,and intermediate binding energy.Finally,the research challenges and prospects are proposed to suggest the future designs of advanced MFEs in CO_(2)RR.展开更多
基金supported by the National Science and Technology Support Project of China(2013BAC11B03)the National Natural Science Foundation of China(21401054,21476065,21273067)the Graduate Student Scientific Research Innovation Fund Project of Hunan Province(CX2015B082)~~
文摘The aim of ＂green chemistry＂ and ＂atom economy＂ is to utilize carbon dioxide and replace harmful reactants such as CO and phosgene for the production of cyclic carbonates. In this paper, metal-free catalysts including organic bases, ionic liquids, supported catalysts, organic copolymers and carbon materials for the synthesis of cyclic carbonates by the cycloaddition of carbon dioxide to epoxides are reviewed. Recent advances in the design of the catalysts and the understanding of the reaction mechanism are summarized and discussed. The synergistic effects of organic bases and hydrogen bond donors, organic bases and nucleophilic anions, hydrogen bond donors and nucleophilic anions and active components and supports are highlighted. The challenge is to develop metal-free catalysts suitable for carbon dioxide capture and fixation. The ultimate goal is to synthesize cyclic carbonates in a flow reactor directly using carbon dioxide from industrial flue gas at ambient temperature and atmospheric pressure. By using synergetic effects, a multi-functional approach can meet the design strategy of metal-free catalysts for carbon dioxide adsorption and activation as well as epoxide ring opening.
基金This work was supported by National Natural Science Foundation of China （Nos. 21331004, 21673140, and 21671134）, Innovation Program of Shanghai Science and Technology Committee （No. 16JC1401600）, Shanghai Eastern Scholar Program, Shanghai Rising-Star Program （No. 16QA1402100） and SJTU-MPI partner group.
文摘The greenhouse effect and global warming are serious problems because the increasing global demand for fossil fuels has led to a rapid rise in greenhouse gas exhaust emissions in the atmosphere and disruptive changes in climate. As a major contributor, CO2 has attracted much attention from scientists, who have attempted to convert it into useful products by electrochemical or photoelectrochemical reduction methods. Facile design of efficient but inexpensive and abundant catalysts to convert CO2 into fuels or valuable chemical products is essential for materials chemistry and catalysis in addressing global climate change as well as the energy crisis. Herein, we show that two-dimensional fewlayer graphitic carbon nitride （g-C3N4） can function as an efficient metal-free electrocatalyst for selective reduction of CO2 to CO at low overpotentials with a high Faradaic efficiency of - 80%. The polarized surface of ultrathin g-C3N4 layers （thickness： -1 nm）, with a more reductive conduction band, yields excellent electrochemical activity for CO2 reduction.
基金supported by the National Key R&D Program of China (2016YFB0600902)the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB17000000)+2 种基金Dalian National Laboratory for Clean Energy (DNL180401)the Youth Innovation Promotion Association CASthe Singapore Ministry of Education Academic Research Fund (AcRF) Tier 1: RG9/17, RG115/17, RG115/18 and Tier 2: MOE2016-T2-2-004
文摘Electrochemical CO2 reduction to chemicals or fuels presents one of the most promising strategies for managing the global carbon balance, which yet poses a significant challenge due to lack of efficient and durable electrocatalyst as well as the understanding of the CO2 reduction reaction(CO2RR) mechanism.Benefiting from the large surface area, high electrical conductivity, and tunable structure, carbon-based metal-free materials(CMs) have been extensively studied as cost-effective electrocatalysts for CO2RR.The development of CMs with low cost, high activity and durability for CO2RR has been considered as one of the most active and competitive directions in electrochemistry and material science.In this review article,some up-to-date strategies in improving the CO2RR performance on CMs are summarized.Specifically, the approaches to optimize the adsorption of CO2RR intermediates, such as tuning the physical and electronic structure are introduced, which can enhance the electrocatalytic activity of CMs effectively.Finally, some design strategies are proposed to prepare CMs with high activity and selectivity for CO2RR.
基金supported by the National Natural Science Foundation of China(Nos.22101105,52071171,52202248)the Research Fund for the Doctoral Program of Liaoning Province(2021-BS-086)+6 种基金Liaoning BaiQianWan Talents Program(LNBQW2018B0048)Shenyang Science and Technology Project(21-108-9-04)Australian Research Council(ARC)through Future Fellowship(FT210100298,FT210100806)Discovery Project(DP220100603)Linkage Project(LP210100467,LP210200504,LP210200345,LP220100088)Industrial Transformation Training Centre(IC180100005)schemesthe Australian Government through the Cooperative Research Centres Projects(CRCPXIII000077).
文摘Covalent organic frameworks(COFs)have emerged as a kind of rising star materials in photocatalysis.However,their photocatalytic activities are restricted by the high photogenerated electron-hole pairs recombination rate.Herein,a novel metal-free 2D/2D van der Waals heterojunction,composed of a two-dimensional(2D)COF with ketoenamine linkage(TpPa-1-COF)and 2D defective hexagonal boron nitride(h-BN),is successfully constructed through in situ solvothermal method.Benefitting from the presence of VDW heterojunction,larger contact area and intimate electronic coupling can be formed between the interface of TpPa-1-COF and defective h-BN,which make contributions to promoting charge car-riers separation.The introduced defects can also endow the h-BN with porous structure,thus providing more reactive sites.Moreover,the TpPa-1-COF will undergo a structural transformation after being integrated with defective h-BN,which can enlarge the gap between the conduction band position of the h-BN and TpPa-1-COF,and suppress electron backflow,corroborated by experimental and density functional theory calculations results.Accordingly,the resulting porous h-BN/TpPa-1-COF metal-free VDW heterojunction displays out-standing solar energy catalytic activity for water splitting without co-catalysts,and the H_(2) evolution rate can reach up to 3.15 mmol g^(−1) h^(−1),which is about 67 times greater than that of pristine TpPa-1-COF,also surpassing that of state-of-the-art metal-free-based photocatalysts reported to date.In particular,it is the first work for constructing COFs-based heterojunctions with the help of h-BN,which may provide new avenue for designing highly efficient metal-free-based photocatalysts for H_(2) evolution.
基金The authors thank our colleagues for their contributions to the work cited.This study was partially supported by the ARC DP190103881,US Air Force Research Laboratory(AFRL),UNSW,and CWRU.
文摘Since the discovery of the first carbon-based metal-free electrocatalysts(C-MFECs,i.e.,N-doped carbon nanotubes)for the oxygen reduction reaction in 2009,the field of C-MFECs has grown enormously over the last 10 years.C-MFECs,as alternatives to nonprecious transition metals and/or precious noble metal-based electrocatalysts,have been consistently demonstrated as efficient catalysts for oxygen reduction,oxygen evolution,hydrogen evolution,carbon dioxide reduction,nitrogen reduction,and many other(electro-)chemical reactions.Recent research and development of C-MFECs have indicated their potential applications in fuel cells,metal-air batteries,and hydrogen generation through water oxidation as well as electrochemical production of various commodity chemicals,such as ammonia,alcohols,hydrogen peroxide,and other useful hydrocarbons.Further research and development of C-MFECs would surely revolutionize traditional energy conversion and storage technologies with minimal environmental impact.In this short review article,we summarize the journey of C-MFECs over the past 10 years with an emphasis on materials development and their structure-property characterization for applications in fuel cells and metal-air batteries.Current challenges and future prospects of this emerging field are also discussed.
基金supported by the Natural Science Foundation of Shandong Province(ZR2019PB013)the Natural Science Foundation of Tianjin(19JCZDJC37700)the National Natural Science Foundation of China(21421001 and 21875118)。
文摘To date,much efforts have been devoted to the high-efficiency noble metal-free electrocatalysts for hydrogen-and oxygen-involving energy conversion reactions,due to their abundance,low cost and nultifunctionally.Surface/interface engineering is found to be effective in achieving novel physicochemical properties and synergistic effects in nanomaterials for electrocatalysis.Among various engineering strategies,heteroatom-doping has been regarded as a most promising method to improve the electrocatalytic performance via the regulation of electronic structure of catalysts,and numerous works were reported on the synthesis method and mechanism investigation of heteroatom-doping electrocatalysts,though the heteroatom-doping can only provide limited active sites.Engineering of other defects such as vacancies and edge sites and construction of heterostructure have shown to open up a potential avenue for the development of noble metal-free electrocatalysts.In addition,surface functionalization can attach various molecules onto the surface of materials to easily modify their physical or chemical properties,being as a promising complement or substitute for offering materials with catalytic properties.This paper gives the insights into the diverse strategies of surface/interface engineering of the highefficiency noble metal-free electrocatalysts for energy-related electrochemical reactions.The significant advances are summarized.The unique advantages and mechanisms for specific applications are highlighted.The current challenges and outlook of this growing field are also discussed.
基金supported by the National Natural Science Foundation of China(21421001,21573115)the Fundamental Research Funds for the Central Universities(63185015)the Foundation of State Key Laboratory of High-efficiency Utilization of Coal and Green Chemical Engineering(2017-K13)~~
文摘Nanocarbon materials have been used as important metal-free catalysts for various reactions including alkane dehydrogenation.However,clarifying the active sites and tuning the nanocarbon structure for direct dehydrogenation have always been significantly challenging owing to the lack of fundamental understanding of the structure and surface properties of carbon materials.Herein,mesoporous carbon materials with different pore ordering and surface properties were synthesized through a soft-templating method with different formaldehyde/resorcinol ratios and carbonization temperatures and used for catalytic dehydrogenation of propane to propylene.The highly ordered mesoporous carbons were found to have higher catalytic activities than disordered and ordered mesoporous carbons,mainly because the highly ordered mesopores favor mass transportation and provide more accessible active sites.Furthermore,mesoporous carbons can provide a large amount of surface active sites owing to their high surface areas,which is favorable for propane dehydrogenation reaction.To control the surface oxygenated functional groups,highly ordered mesoporous carbons were carbonized at different temperatures(600,700,and 800℃).The propylene formation rates exhibit an excellent linear relationship with the number of ketonic C=O groups,suggesting that C=O groups are the most possible active sites.
基金supported by the National Natural Science Foundation of China (20634020,50703033,20974098 and 20974028)the Ministry of Science and Technology of China (2009CB623605)+4 种基金the University Grants Committee of Hong Kong ( AoE/P-03/08)the Research Grants Council of Hong Kong (603509,601608 and 602707)the Innovation and Technology Fund of Hong Kong (ITS/168/09). A.J.Q. and B.Z.T acknowledge the supports from the Postdoctoral Research Foundation of China (20081461)the Fundamental Research Funds for the Central Universities (2010KYJD005)the CAO GuangBiao Foundation of Zhejiang University,respectively
文摘Regioseletive 1,3-dipolar polycycloadditions of 4,4'-isopropylidenediphenyl dipropiolate (1) and tetraphenylethene (TPE)-containing diazides (2) are carried out in polar solvents such as DMF/toluene at a moderate temperature of 100℃ for 6 h,producing poly(aroxycarbonyltriazole)s (PACTs) P3 with high molecular weights (Mw up to 23900) and regioregularities (F1,4 up to ～90%) in high yields (up to ～99%).These metal-free click polymerizations can propagate smoothly in an open atmosphere without protection from oxygen and moisture.The obtained polymers are soluble in common organic solvents and thermally stable at temperatures up to 375℃.Thanks to their contained TPE moieties,the PACTs show aggregation-induced emission and can serve as fluorescent chemosensors for superamplified detection of explosives.
文摘Ordered macroporous materials with rapid mass transport and enhanced active site accessibility are essential for achieving improved catalytic activity.In this study,boron phosphate crystals with a three-dimensionally interconnected ordered macroporous structure and a robust framework were fabricated and used as stable and selective catalysts in the oxidative dehydrogenation(ODH)of propane.Due to the improved mass diffusion and higher number of exposed active sites in the ordered macroporous structure,the catalyst exhibited a remarkable olefin productivity of^16 golefin gcat^-1 h^-1,which is up to 2–100 times higher than that of ODH catalysts reported to date.The selectivity for olefins was 91.5%(propene:82.5%,ethene:9.0%)at 515℃,with a propane conversion of 14.3%.At the same time,the selectivity for the unwanted deep-oxidized CO2 product remained less than 1.0%.The tri-coordinated surface boron species were identified as the active catalytic sites for the ODH of propane.This study provides a route for preparing a new type of metal-free catalyst with stable structure against oxidation and remarkable catalytic activity,which may represent a potential candidate to promote the industrialization of the ODH process.
基金supported by the National Natura Science Foundation of China (21788102, 21722603, 21476075)Pro gramme of Introducing Talents of Discipline to Universities (B1607)an the Innovation Program of Shanghai Municipal Education Commission an the Fundamental Research Funds for the Central Universities
文摘Room-temperature phosphorescence(RTP) has attracted much attention due to its potential applications in the fields of biological imaging, chemical sensors and so forth. Particularly, amorphous metal-free RTP materials show special advantages of low cost and good processability. In addition, non-conjugated polymers have seldom been reported as phosphorescent materials.In this work, a novel non-conjugated amorphous metal-free copolymer composed of brominated olefins and acrylamide was prepared in a facile way, which could engender blue-purple RTP emission. Polymers with different kinds of brominated olefins and different ratios of two monomers have been investigated with the purpose of researching the composition/property relationship that may affect the RTP properties. This unique phenomenon could be due to the clustering of carbonyl and amino units caused molecular interaction, and the heavy-atom effect enhanced intersystem crossing. Meantime, the hydrogen bonding in the system enhanced the conformation rigidification to reduce the non-radiative decay. This work provided a delicate way to construct non-conjugated metal-free RTP materials and supplied a new insight into the development of RTP materials.
基金financial supports by the Young Scientists Fund of the National Natural Science Foundation of China (11604249)the Fok Ying-Tong Education Foundation for Young Teachers in the Higher Education Institutions of China (161008)+3 种基金the Foundation of the State Key Laboratory of Optical Fiber and Cable Manufacture Technology (SKLD1602)the State Key Laboratory of Refractors and Metallurgy (G201605), the Fundamental Research Funds for the Central Universities (2019-III-034)the Research Board of the State Key Laboratory of Silicate Materials for Architecturesfinancial supports and grants from Xiamen University Malaysia,the Xiamen University Malaysia Research Fund (XMUMRF/2019-C3/ IENG/0013)
文摘The development of highly active and low-cost catalysts for electrochemical reactions is one of the most attractive topics in the renewable energy technology.Herein,the site-specific nitrogen doping of graphdiyne(GDY)including grap-N,sp-N(Ⅰ)and sp-N(Ⅱ)GDY is systematically investigated as metal-free oxygen reduction electrocatalysts via density functional theory(DFT).Our results indicate that the doped nitrogen atom can significantly improve the oxygen(O2)adsorption activity of GDY through activating its neighboring carbon atoms.The free-energy landscape is employed to describe the electrochemical oxygen reduction reaction(ORR)in both O2 dissociation and association mechanisms.It is revealed that the association mechanism can provide higher ORR onset potential than dissociation mechanism on most of the substrates.Especially,sp-N(Ⅱ)GDY exhibits the highest ORR electrocatalytic activity through increasing the theoretical onset potential to 0.76 V.This work provides an atomic-level insight for the electrochemical ORR mechanism on metal-free N-doped GDY.
基金National Key R&D Program of China,Grant/Award Number:2020YFA0710000National Natural Science Foundation of China,Grant/Award Numbers:21573066,21902047,21825201,22075075,22173048,and U1932212China Postdoctoral Science Foundation,Grant/Award Numbers:2020M682540,BX20200116。
文摘Electrocatalytic urea synthesis via coupling of nitrate with CO_(2)is considered as a promising alternative to the industrial urea synthetic process.However,the requirement of sub-reaction(NO_(3)RR and CO_(2)RR)activities for efficient urea synthesis is not clear and the related reaction mechanisms remain obscure.Here,the construction,breaking,and rebuilding of the sub-reaction activity balance would be accompanied by the corresponding regulation in urea synthesis,and the balance of sub-reaction activities was proven to play a vital role in efficient urea synthesis.With rational design,a urea yield rate of 610.6 mg h−1 gcat.−1 was realized on the N-doped carbon electrocatalyst,superior to that of noble-metal electrocatalysts.Based on the operando SRFTIR measurements,we proposed that urea synthesis arises from the coupling of^(*)NO and^(*)CO to generate the key intermediate of^(*)OCNO.This work provides new insights and guidelines into urea synthesis from the aspect of activity balance.
基金CSIRO Energy Centre and Kick‐Start ProjectAustralian Research Council(ARC)Future Fellowships,Grant/Award Numbers:FT210100298,FT210100806+9 种基金Key Project of Scientific Research of the Education Department of Liaoning Province,Grant/Award Number:LZD201902National Natural Science Foundation of China,Grant/Award Numbers:51873085,52071171Liaoning Revitalization Talents Program‐Pan Deng Scholars,Grant/Award Numbers:XLYC1802005,XLYC2007056Industrial Transformation Training Centre,Grant/Award Number:IC180100005Shenyang Science and Technology Project,Grant/Award Number:21‐108‐9‐04veski-Study Melbourne Research Partnerships(SMRP)projectLiaoning BaiQianWan Talents Program,Grant/Award Number:LNBQW2018B0048Natural Science Fund of Liaoning Province for Excellent Young Scholars,Grant/Award Number:2019‐YQ‐04Discovery Project,Grant/Award Number:DP220100603Linkage project,Grant/Award Number:LP210100467。
文摘The electrochemical reduction of carbon dioxide(CO_(2))into value‐added fuels and chemicals presents a sustainable route to alleviate CO_(2) emissions,promote carbon‐neutral cycles and reduce the dependence on fossil fuels.Considering the thermodynamic stability of the CO_(2) molecule and sluggish reaction kinetics,it is still a challenge to design highly efficient electrocatalysts for the CO_(2) reduction reaction(CO_(2)RR).It has been found that the surface and interface chemistry of electrocatalysts can modulate the electronic structure and increase the active sites,which is favorable for CO_(2) adsorption,electron transfer,mass transport,and optimizing adsorption strength of reaction intermediates.However,the effect of surface and interface chemistry on metal‐free electrocatalysts(MFEs)for CO_(2)RR has not been comprehensively reviewed.Herein,we discuss the importance of the surface and interface chemistry on MFEs for improving the electrochemical CO_(2)RR performance based on thermodynamic and kinetic views.The fundamentals and challenges of CO_(2)RR are firstly presented.Then,the recent advances of the surface and interface chemistry in improving reaction rate and overcoming reaction constraints are reviewed from regulating electronic structure,active sites,electron transfer,mass transport,and intermediate binding energy.Finally,the research challenges and prospects are proposed to suggest the future designs of advanced MFEs in CO_(2)RR.
