The two-electron oxygen reduction reaction(ORR)for H_(2)O_(2) photosynthesis is often hindered by sluggish charge kinetics and a limited number of activation sites.Theoretical predictions based on dipole moment analys...The two-electron oxygen reduction reaction(ORR)for H_(2)O_(2) photosynthesis is often hindered by sluggish charge kinetics and a limited number of activation sites.Theoretical predictions based on dipole moment analysis indicate that introducing pyrazine units enhances charge migration,leading to increased accumulation of photoinduced electrons on these units,thereby facilitating the two-site,two-electron ORR.Inspired by these theoretical insights,this work designed and fabricated a triazine-pyrazine-based covalent organic framework materials(TTDN-COFs)for H_(2)O_(2) photosynthesis via a polarity-functionalization strategy.The TTDN-COFs demonstrate a significant improvement in the photocatalytic H_(2)O_(2) production rate,reaching 2757.6μmol h^(-1) g^(-1) in pure water–3.2 times higher than that of the triazine-based COFs(TTPH-COFs).Experimental results and theoretical calculations confirm that the incorporation of pyrazine units not only enhances polarization,promoting the separation and migration of charge carriers,but also facilitates the formation of endoperoxide at both the triazine and pyrazine units.The dual adsorption activation sites lower the activation energy barrier for O_(2),thereby accelerating the overall reaction kinetics.These findings highlight the potential of functional-group-mediated polarization engineering as a promising strategy for developing COFs-based H_(2)O_(2) photosynthesis with dual activation sites.展开更多
Two-dimensional covalent organic frameworks(COFs)with specific morphologies including nanofibers and nanoplates are highly desired in both nanoscience research and practical applications.Thus far,however,morphology en...Two-dimensional covalent organic frameworks(COFs)with specific morphologies including nanofibers and nanoplates are highly desired in both nanoscience research and practical applications.Thus far,however,morphology engineering for COFs remains challenging because the mechanism underlying the morphology formation and evolution of COFs is not well understood.Herein,we propose a strategy of surfactant mediation coupled with acid adjustment to engineer the morphology of aβ-ketoenamine-linked COF,TpPa,during solvothermal synthesis.The surfactants function as stabilizers that can encapsulate monomers and prepolymers to create micelles,enabling the formation of fiber-like and plate-like morphologies of TpPa rather than irregularly shaped aggregates.It is also found that acetic acid is important in regulating such morphologies,as the amino groups inside the prepolymers can be precisely protonated by acid adjustment,leading to an inhibited ripening process for the creation of specific morphologies.Benefitting from the synergistic enhancement of surfactant mediation and acid adjustment,TpPa nanofibers with a diameter down to~20 nm along with a length of up to a few microns and TpPa nanoplates with a thickness of~18 nm are created.Our work sheds light on the mechanism underlying the morphology formation and evolution of TpPa,providing some guidance for exquisite control over the growth of COFs,which is of great significance for their practical applications.展开更多
Metal-free carbon catalysts with excellent conduction performance have drawn much research attention in reduction reactions.Herein,a N,B co-doped carbon catalyst with high pyrrolic N proportion(35.75%)and excellent su...Metal-free carbon catalysts with excellent conduction performance have drawn much research attention in reduction reactions.Herein,a N,B co-doped carbon catalyst with high pyrrolic N proportion(35.75%)and excellent surface area(1409 m^(2)/g)was successfully prepared via carbonizing covalent organic framework materials(COFs)containing N and B atoms assisted by ZnCl_(2)molten salt.The presence of ZnCl_(2)maintains the micropore structure of COFs to provide high specific surface areas and abundant lattice defects for carbon materials.In addition,electron-withdrawing B heteroatom further facilitates the formation of pyrrolic N at defect sites by modifying the electronic structure of carbon network.The tuning of surface areas and active N species in carbon catalysts successfully improve the selective hydrogenation of nitrobenzene to aniline.The optimized carbon material exhibits excellent nitrobenzene conversion(99.9%)and aniline selectivity(>99%)within 15 min,as well as excellent substrate suitability.This work provides a certain guiding for the design and application of metal-free catalysis.展开更多
Covalent organic frameworks(COFs)are an emerging class of photoactive materials,solely composed of light elements.Their ordered structure,crystallinity,and high porosity led to enormous worldwide attention in many res...Covalent organic frameworks(COFs)are an emerging class of photoactive materials,solely composed of light elements.Their ordered structure,crystallinity,and high porosity led to enormous worldwide attention in many research fields.The extensiveπ-electron conjugation,light-harvesting and charge transport characteristics make them a fascinating polymer for photocatalytic systems.Versatile selection of building blocks and innumerable synthetic methodologies enable them to be a robust platform for solar energy production.In this mini-review,we summarized recent progress and challenges of the design,construction,and applications of COFs-based photocatalysts,and also presented some perspectives on challenges.展开更多
Traditional fossil fuels significantly contribute to energy supply,economic development,and advancements in science and technology.However,prolonged and extensive use of fossil fuels has resulted in increasingly sever...Traditional fossil fuels significantly contribute to energy supply,economic development,and advancements in science and technology.However,prolonged and extensive use of fossil fuels has resulted in increasingly severe environmental pollution.Consequently,it is imperative to develop new,clean,and pollution-free energy sources with high energy density and versatility as substitutes for conventional fossil fuels,although this remains a considerable challenge.Simultaneously,addressing water pollution is a critical concern.The development,design,and optimization of functional nanomaterials are pivotal to advancing new energy solutions and pollutant remediation.Emerging porous framework materials such as metal-organic frameworks(MOFs)and covalent organic frameworks(COFs),recognized as exemplary crystalline porous materials,exhibit potential in energy and environmental applications due to their high specific surface area,adjustable pore sizes and structures,permanent porosity,and customizable functionalities.This work provides a comprehensive and systematic review of the applications of MOFs,COFs,and their derivatives in emerging energy technologies,including the oxygen reduction reaction,oxygen evolution reaction,hydrogen evolution reaction,lithium-ion batteries,and environmental pollution remediation such as the carbon dioxide reduction reaction and environmental pollution management.In addition,strategies for performance adjustment and the structure-effect relationships of MOFs,COFs,and their derivatives for these applications are explored.Interaction mechanisms are summarized based on experimental discussions,theoretical calculations,and advanced spectroscopy analyses.The challenges,future prospects,and opportunities for tailoring these materials for energy and environmental applications are presented.展开更多
MXenes,a class of two-dimensional(2D)transition metal carbides,and covalent organic frameworks(COFs)deliver unique structural and electrochemical properties,making them promising candidates for energy storage and conv...MXenes,a class of two-dimensional(2D)transition metal carbides,and covalent organic frameworks(COFs)deliver unique structural and electrochemical properties,making them promising candidates for energy storage and conversion applications.MXenes exhibit excellent conductivity and tunable surface chemistries,whereas the COFs provide high porosity and structural versatility.Recent advances in integrating MXene-COF composites have revealed their potential to enhance charge transfer and energy storage/conversion properties.The work highlights key developments in MXene-COF integration,offering insights into their applications in batteries(Li-ion,K-ion,Na-ion,and Li-S),supercapacitors,and electrocatalysis(HER,OER,RR,NRR,and ORRCO2),while also addressing current challenges and future directions for not only energy conversion but also other electronic devices.展开更多
The chemical structure of covalent organic frameworks(COFs)plays a key role in their response to the surface doping strategy used for tuning their electronic character,but it is still not fully understood.To explore a...The chemical structure of covalent organic frameworks(COFs)plays a key role in their response to the surface doping strategy used for tuning their electronic character,but it is still not fully understood.To explore a rational design proposal for their chemical structure,the electronic properties of three n-doped typical COFs,including boroncontaining(COF-1),triazine-based(CTF),and C–C bondlinked(GCOF)COFs,were investigated theoretically in this work.As expected,the chemical doping effects are different for these COFs.The dispersion of the frontier bands,the nuclear-independent chemical shift(NICS)aromaticity index results,distribution of the electron localization function(ELF),and Hirshfeld charge population plots show that part of the transferred electron from dopants will be offset by the intralayer charge transfer of COFs.Thus,chemical doping effects are more significant if the electron distribution in the COFs is more localized.This means the response of COFs to the surface doping strategy should be dominated by the conjugation degree of their chemical structure.Our results prove that the intrinsic conjugation degree of COFs plays a key role in such doping functionalization strategies,which are expected to provide more useful information for the initial structure design of COF materials and facilitate their practical applications as active electronic transport materials in nanoscale devices.展开更多
Three large π-conjugated and imine-based COFs,named TFP-TAB,TFP-TTA,and TTA-TTB,were synthesized via the ordered incorporation of benzene and triazine rings in the same host framework to study how the structural unit...Three large π-conjugated and imine-based COFs,named TFP-TAB,TFP-TTA,and TTA-TTB,were synthesized via the ordered incorporation of benzene and triazine rings in the same host framework to study how the structural units affect the efficiency of CO_(2)photoreduction.Results from both experiments and density-functional theory(DFT)calculations indicate the separation and transfer of the photoinduced charges is highly related to the triazine-N content and the conjugation degree in the skeletons of COFs.High-efficiency CO_(2)photoreduction can be achieved by rationally adjusting the number and position of both benzene and triazine rings in the COFs.Specifically,TTA-TTB,with orderly interlaced triazine-benzene heterojunctions,can suppress the recombination probability of electrons and holes,which effectively immobilizes the key species(COOH)and lowers the free energy change of the potential-determining step,and thus exhibits a superior visible-light-induced photocatalytic activity that yields 121.7 μmol HCOOH g^(-1)h^(-1).This research,therefore,helps to elucidate the effects of the different structural blocks in COFs on inherent heterogeneous photocatalysis for CO_(2)reduction at a molecular level.展开更多
文摘The two-electron oxygen reduction reaction(ORR)for H_(2)O_(2) photosynthesis is often hindered by sluggish charge kinetics and a limited number of activation sites.Theoretical predictions based on dipole moment analysis indicate that introducing pyrazine units enhances charge migration,leading to increased accumulation of photoinduced electrons on these units,thereby facilitating the two-site,two-electron ORR.Inspired by these theoretical insights,this work designed and fabricated a triazine-pyrazine-based covalent organic framework materials(TTDN-COFs)for H_(2)O_(2) photosynthesis via a polarity-functionalization strategy.The TTDN-COFs demonstrate a significant improvement in the photocatalytic H_(2)O_(2) production rate,reaching 2757.6μmol h^(-1) g^(-1) in pure water–3.2 times higher than that of the triazine-based COFs(TTPH-COFs).Experimental results and theoretical calculations confirm that the incorporation of pyrazine units not only enhances polarization,promoting the separation and migration of charge carriers,but also facilitates the formation of endoperoxide at both the triazine and pyrazine units.The dual adsorption activation sites lower the activation energy barrier for O_(2),thereby accelerating the overall reaction kinetics.These findings highlight the potential of functional-group-mediated polarization engineering as a promising strategy for developing COFs-based H_(2)O_(2) photosynthesis with dual activation sites.
基金the National Natural Science Foundation of China(No.21921006).
文摘Two-dimensional covalent organic frameworks(COFs)with specific morphologies including nanofibers and nanoplates are highly desired in both nanoscience research and practical applications.Thus far,however,morphology engineering for COFs remains challenging because the mechanism underlying the morphology formation and evolution of COFs is not well understood.Herein,we propose a strategy of surfactant mediation coupled with acid adjustment to engineer the morphology of aβ-ketoenamine-linked COF,TpPa,during solvothermal synthesis.The surfactants function as stabilizers that can encapsulate monomers and prepolymers to create micelles,enabling the formation of fiber-like and plate-like morphologies of TpPa rather than irregularly shaped aggregates.It is also found that acetic acid is important in regulating such morphologies,as the amino groups inside the prepolymers can be precisely protonated by acid adjustment,leading to an inhibited ripening process for the creation of specific morphologies.Benefitting from the synergistic enhancement of surfactant mediation and acid adjustment,TpPa nanofibers with a diameter down to~20 nm along with a length of up to a few microns and TpPa nanoplates with a thickness of~18 nm are created.Our work sheds light on the mechanism underlying the morphology formation and evolution of TpPa,providing some guidance for exquisite control over the growth of COFs,which is of great significance for their practical applications.
基金National Natural Science Foundation of China(Nos.21776129 and 21706121)Natural Science Foundation of Jiangsu Province(No.BK20170995)+1 种基金Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.KYCX211171)the Project of Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)。
文摘Metal-free carbon catalysts with excellent conduction performance have drawn much research attention in reduction reactions.Herein,a N,B co-doped carbon catalyst with high pyrrolic N proportion(35.75%)and excellent surface area(1409 m^(2)/g)was successfully prepared via carbonizing covalent organic framework materials(COFs)containing N and B atoms assisted by ZnCl_(2)molten salt.The presence of ZnCl_(2)maintains the micropore structure of COFs to provide high specific surface areas and abundant lattice defects for carbon materials.In addition,electron-withdrawing B heteroatom further facilitates the formation of pyrrolic N at defect sites by modifying the electronic structure of carbon network.The tuning of surface areas and active N species in carbon catalysts successfully improve the selective hydrogenation of nitrobenzene to aniline.The optimized carbon material exhibits excellent nitrobenzene conversion(99.9%)and aniline selectivity(>99%)within 15 min,as well as excellent substrate suitability.This work provides a certain guiding for the design and application of metal-free catalysis.
基金This work was financially supported by the National Natural Science Foundation of China(No.21975086)the International S&T Cooperation Program of China(No.2018YFE010498)+2 种基金the HUST Innovation Funding(No.2018JYCXJJ041)Science and Technology Department of Hubei Province(Nos.2019CFA008 and 2018AAA057)the Program for HUST Interdisciplinary Innovation Team(No.2016JCTD104).
文摘Covalent organic frameworks(COFs)are an emerging class of photoactive materials,solely composed of light elements.Their ordered structure,crystallinity,and high porosity led to enormous worldwide attention in many research fields.The extensiveπ-electron conjugation,light-harvesting and charge transport characteristics make them a fascinating polymer for photocatalytic systems.Versatile selection of building blocks and innumerable synthetic methodologies enable them to be a robust platform for solar energy production.In this mini-review,we summarized recent progress and challenges of the design,construction,and applications of COFs-based photocatalysts,and also presented some perspectives on challenges.
基金supported by the National Natural Science Foundation of China(22327807,U2067215,U2341289,22341602,22006036,U2167218,22276054).
文摘Traditional fossil fuels significantly contribute to energy supply,economic development,and advancements in science and technology.However,prolonged and extensive use of fossil fuels has resulted in increasingly severe environmental pollution.Consequently,it is imperative to develop new,clean,and pollution-free energy sources with high energy density and versatility as substitutes for conventional fossil fuels,although this remains a considerable challenge.Simultaneously,addressing water pollution is a critical concern.The development,design,and optimization of functional nanomaterials are pivotal to advancing new energy solutions and pollutant remediation.Emerging porous framework materials such as metal-organic frameworks(MOFs)and covalent organic frameworks(COFs),recognized as exemplary crystalline porous materials,exhibit potential in energy and environmental applications due to their high specific surface area,adjustable pore sizes and structures,permanent porosity,and customizable functionalities.This work provides a comprehensive and systematic review of the applications of MOFs,COFs,and their derivatives in emerging energy technologies,including the oxygen reduction reaction,oxygen evolution reaction,hydrogen evolution reaction,lithium-ion batteries,and environmental pollution remediation such as the carbon dioxide reduction reaction and environmental pollution management.In addition,strategies for performance adjustment and the structure-effect relationships of MOFs,COFs,and their derivatives for these applications are explored.Interaction mechanisms are summarized based on experimental discussions,theoretical calculations,and advanced spectroscopy analyses.The challenges,future prospects,and opportunities for tailoring these materials for energy and environmental applications are presented.
基金Hong Kong Innovation and Technology Commission,Grant/Award Number:GHP/247/22GD。
文摘MXenes,a class of two-dimensional(2D)transition metal carbides,and covalent organic frameworks(COFs)deliver unique structural and electrochemical properties,making them promising candidates for energy storage and conversion applications.MXenes exhibit excellent conductivity and tunable surface chemistries,whereas the COFs provide high porosity and structural versatility.Recent advances in integrating MXene-COF composites have revealed their potential to enhance charge transfer and energy storage/conversion properties.The work highlights key developments in MXene-COF integration,offering insights into their applications in batteries(Li-ion,K-ion,Na-ion,and Li-S),supercapacitors,and electrocatalysis(HER,OER,RR,NRR,and ORRCO2),while also addressing current challenges and future directions for not only energy conversion but also other electronic devices.
基金supported by the Key Program of the National Natural Science Foundation of China(52336003)the National Natural Science Foundation of China(22373054,52176076)+2 种基金the Natural Science Foundation of Shandong Province(ZR2020MB045)the Key R&D Program of Shandong Province(Major Science and Technology Innovation Project)(2023CXGC010315)the Taishan Scholar Project of Shandong Province(China)(ts20190937).
文摘The chemical structure of covalent organic frameworks(COFs)plays a key role in their response to the surface doping strategy used for tuning their electronic character,but it is still not fully understood.To explore a rational design proposal for their chemical structure,the electronic properties of three n-doped typical COFs,including boroncontaining(COF-1),triazine-based(CTF),and C–C bondlinked(GCOF)COFs,were investigated theoretically in this work.As expected,the chemical doping effects are different for these COFs.The dispersion of the frontier bands,the nuclear-independent chemical shift(NICS)aromaticity index results,distribution of the electron localization function(ELF),and Hirshfeld charge population plots show that part of the transferred electron from dopants will be offset by the intralayer charge transfer of COFs.Thus,chemical doping effects are more significant if the electron distribution in the COFs is more localized.This means the response of COFs to the surface doping strategy should be dominated by the conjugation degree of their chemical structure.Our results prove that the intrinsic conjugation degree of COFs plays a key role in such doping functionalization strategies,which are expected to provide more useful information for the initial structure design of COF materials and facilitate their practical applications as active electronic transport materials in nanoscale devices.
基金support from the Scientific Research Fund of Zhejiang Provincial Education Department(Y202353855)the Zhejiang Provincial Key R&D Project(2021C01056)+1 种基金the Programme of Introducing Talents of Discipline to Universities(No.D17008)the National Natural Science Foundation of China(22208312).
文摘Three large π-conjugated and imine-based COFs,named TFP-TAB,TFP-TTA,and TTA-TTB,were synthesized via the ordered incorporation of benzene and triazine rings in the same host framework to study how the structural units affect the efficiency of CO_(2)photoreduction.Results from both experiments and density-functional theory(DFT)calculations indicate the separation and transfer of the photoinduced charges is highly related to the triazine-N content and the conjugation degree in the skeletons of COFs.High-efficiency CO_(2)photoreduction can be achieved by rationally adjusting the number and position of both benzene and triazine rings in the COFs.Specifically,TTA-TTB,with orderly interlaced triazine-benzene heterojunctions,can suppress the recombination probability of electrons and holes,which effectively immobilizes the key species(COOH)and lowers the free energy change of the potential-determining step,and thus exhibits a superior visible-light-induced photocatalytic activity that yields 121.7 μmol HCOOH g^(-1)h^(-1).This research,therefore,helps to elucidate the effects of the different structural blocks in COFs on inherent heterogeneous photocatalysis for CO_(2)reduction at a molecular level.
