Supported noble metal nanoparticles （including nanoclusters） are widely used in many industrial catalytic processes. While the finely dispersed nanostructures are highly active, they are usually thermodynamically un...Supported noble metal nanoparticles （including nanoclusters） are widely used in many industrial catalytic processes. While the finely dispersed nanostructures are highly active, they are usually thermodynamically unstable and tend to aggregate or sinter at elevated temperatures. This scenario is particularly true for supported nanogold catalysts because the gold nanostructures are easily sintered at high temperatures, under reaction conditions, or even during storage at ambient temperature. Here, we demonstrate that isolated Au single atoms dispersed on iron oxide nanocrystallites （Aul/FeOx） are much more sintering- resistant than Au nanostructures, and exhibit extremely high reaction stability for CO oxidation in a wide temperature range. Theoretical studies revealed that the positively charged and surface-anchored Aul atoms with high valent states formed significant covalent metal-support interactions （CMSIs）, thus providing the ultra-stability and remarkable catalytic performance. This work may provide insights and a new avenue for fabricating supported Au catalysts with ultra-high stability.展开更多
Graphene has attracted the interest of chemists, physicists, and materials scientists due to its extraordinary structural, mechanical, and electronic properties. While pristine graphene is desirable for applications t...Graphene has attracted the interest of chemists, physicists, and materials scientists due to its extraordinary structural, mechanical, and electronic properties. While pristine graphene is desirable for applications that require a high electrical conductivity, many other applications require modified or functionalized forms of graphene, such as graphene oxide, reduced graphene, or other functionalized forms. Structurally modifying graphene through chemical functionalization reveals the numerous possibilities for tuning its structure; several chemical and physical functionalization methods have been explored to improve the stabilization and modification of graphene. In this review, we report recent progress towards the chemical modification of graphene, including both covalent and noncovalent methods, for use in various applications.展开更多
Covalent organic frameworks(COFs)are a new type of crystalline porous polymers known for chemical stability,excellent structural regularity,robust framework,and inherent porosity,making them promising materials for ca...Covalent organic frameworks(COFs)are a new type of crystalline porous polymers known for chemical stability,excellent structural regularity,robust framework,and inherent porosity,making them promising materials for capturing various types of pollutants from aqueous solutions.This review thoroughly presents the recent progress and advances of COFs and COF-based materials as superior adsorbents for the efficient removal of toxic heavy metal ions,radionuclides,and organic pollutants.Information about the interaction mechanisms between various pollutants and COF-based materials are summarized from the macroscopic and microscopic standpoints,including batch experiments,theoretical calculations,and advanced spectroscopy analysis.The adsorption properties of various COF-based materials are assessed and compared with other widely used adsorbents.Several commonly used strategies to enhance COF-based materials’adsorption performance and the relationship between structural property and sorption ability are also discussed.Finally,a summary and perspective on the opportunities and challenges of COFs and COF-based materials are proposed to provide some inspiring information on designing and fabricating COFs and COF-based materials for environmental pollution management.展开更多
Base excision repair （BER） is an evolutionarily conserved process for maintaining genomic integrity by eliminating several dozen damaged （oxidized or aikylated） or inappropriate bases that are generated endogenous...Base excision repair （BER） is an evolutionarily conserved process for maintaining genomic integrity by eliminating several dozen damaged （oxidized or aikylated） or inappropriate bases that are generated endogenously or induced by genotoxicants, predominantly, reactive oxygen species （ROS）. BER involves 4-5 steps starting with base excision by a DNA glycosylase, followed by a common pathway usually involving an AP-endonuclease （APE） to generate 3＇ OH terminus at the damage site, followed by repair synthesis with a DNA polymerase and nick sealing by a DNA iigase. This pathway is also responsible for repairing DNA single-strand breaks with blocked termini directly generated by ROS. Nearly all glycosylases, far fewer than their substrate lesions particularly for oxidized bases, have broad and overlapping substrate range, and could serve as back-up enzymes in vivo. In contrast, mammalian cells encode only one APE, APEI, unlike two APEs in lower organisms. In spite of overall similarity, BER with distinct subpathways in the mammals is more complex than in E. coli. The glycosylases form complexes with downstream proteins to carry out efficient repair via distinct subpathways one of which, responsible for repair of strand breaks with 3＇ phosphate termini generated by the NEIL family glycosylases or by ROS, requires the phosphatase activity of polynucleotide kinase instead of APE1. Different complexes may utilize distinct DNA polymerases and iigases. Mammalian glycosylases have nonconserved extensions at one of the termini, dispensable for enzymatic activity but needed for interaction with other BER and non-BER proteins for complex formation and organeile targeting. The mammalian enzymes are sometimes covalently modified which may affect activity and complex formation. The focus of this review is on the early steps in mammalian BER for oxidized damage.展开更多
Environmental pollution is one of the most serious problems facing mankind today,and has attracted widespread attention worldwide. The burgeoning class of crystalline porous organic framework materials, metal–organic...Environmental pollution is one of the most serious problems facing mankind today,and has attracted widespread attention worldwide. The burgeoning class of crystalline porous organic framework materials, metal–organic frameworks and covalent organic frameworks present promising application potential in areas related to pollution control due to their interesting surface properties. In this review, the literature of the past five years on the adsorptive removal of various hazardous materials, mainly including heavy metal ions, harmful gases, organic dyes, pharmaceutical and personal care products, and radionuclides from the environment by using COFs and MOFs, is summarized. The adsorption mechanisms are also discussed to help understand their adsorption performance and selectivity. Additionally, some insightful suggestions are given to enhance the performance of MOFs and COFs in the adsorptive removal of various hazardous materials.展开更多
Lithium metal(Li)is believed to be the ultimate anode for lithium-ion batteries(LIBs)owing to the advantages of high theoretical capacity,the lowest electrochemical potential,and light weight.Nevertheless,issues such ...Lithium metal(Li)is believed to be the ultimate anode for lithium-ion batteries(LIBs)owing to the advantages of high theoretical capacity,the lowest electrochemical potential,and light weight.Nevertheless,issues such as uncontrollable growth of Li dendrites,large volume changes,high chemical reactivity,and unstable solid electrolyte interphase(SEI)hinder its rapid development and practical application.Herein a stable and dendrite-free Li-metal anode is obtained by designing a flexible and freestanding MXene/COF framework for metallic Li.COF-LZU1 microspheres are distributed among the MXene film framework.Lithiophilic COF-LZU1 microspheres as nucleation seeds can promote uniform Li nucleation by homogenizing the Li^(+)flux and lowering the nucleation barrier,finally resulting in dense and dendrite-free Li deposition.Under the regulation of the COF-LZU1 seeds,the Coulombic efficiency of the MXene/COF-LZU1 framework and electrochemical stability of corresponding symmetric cells are obviously enhanced.Li-S full cells with the modified Li-metal anode and sulfurized polyacrylonitrile(S@PAN)cathode also exhibited a superior electrochemical performance.展开更多
Covalent organic frameworks（COFs） are an emerging class of porous covalent organic structures whose backbones were composed of light elements（B,C,N,O,Si） and linked by robust covalent bonds to endow such material ...Covalent organic frameworks（COFs） are an emerging class of porous covalent organic structures whose backbones were composed of light elements（B,C,N,O,Si） and linked by robust covalent bonds to endow such material with desirable properties,i.e.,inherent porosity,well-defined pore aperture,ordered channel structure,large surface area,high stability,and multi-dimension.As expected,the abovementioned properties of COFs broaden the applications of this class of materials in various fields such as gas storage and separation,catalysis,optoelectronics,sensing,small molecules adsorption,and drug delivery.In this review,we outlined the synthesis of COFs and highlighted their applications ranging from the initial gas storage and separation to drug delivery.展开更多
Lewis developed a 2D-representation of molecules, charged or uncharged, known as structural formula, and stated the criteria to draw it. At the time, the vast majority of known molecules followed the octet-rule, one o...Lewis developed a 2D-representation of molecules, charged or uncharged, known as structural formula, and stated the criteria to draw it. At the time, the vast majority of known molecules followed the octet-rule, one of Lewis’s criteria. The same method was however rapidly applied to represent compounds that do not follow the octet-rule, i.e. compounds for which some of the composing atoms have greater or less than eight electrons in their valence shell. In a previous paper, an even-odd rule was proposed and shown to apply to both types of uncharged molecules. In the present paper, the even-odd rule is extended with the objective to encompass all single-bonded ions in one group: Lewis’s ions, hypo- and hypervalent ions. The base of the even-odd representation is compatible with Lewis’s diagram. Additionally, each atom is subscripted with an even number calculated by adding the valence number, the number of covalent bonds of the element, and its electrical charge. This paper describes how to calculate the latter number and in doing so, how charge and electron-pairs can actually be precisely localized. Using ions known to be compatible with Lewis’s rule of eight, the even-odd rule is compared with the former. The even-odd rule is then applied to ions known as hypo- or hypervalent. An interesting side effect of the presented rule is that charge and electron-pairs are unambiguously assigned to one of the atoms composing the single-charged ion. Ions that follow the octet rule and ions that do not, are thus reconciled in one group called “electron-paired ions” due to the absence of unpaired electrons. A future paper will focus on the connection between the even-odd rule and molecules or ions having multiple bonds.展开更多
Covalent organic frameworks（COFs） as an emerging class of porous materials have achieved remarkable progress in recent years.Their high surface area,low mass densities,highly ordered periodic structures,and ease of ...Covalent organic frameworks（COFs） as an emerging class of porous materials have achieved remarkable progress in recent years.Their high surface area,low mass densities,highly ordered periodic structures,and ease of functionalization make COFs exhibit superior potential in gas storage and separation,optoelectronic device and catalysis.This mini review gives a brief introduction of COFs and highlights their applications in electronic and optical fields.展开更多
Covalent organic frameworks(COFs)are a class of organic porous polymers with high crystallinity,and their structures can be precisely tailored via topology design.Owing to the characteristics of permanent pores,period...Covalent organic frameworks(COFs)are a class of organic porous polymers with high crystallinity,and their structures can be precisely tailored via topology design.Owing to the characteristics of permanent pores,periodic structures and rich building blocks,COFs have triggered tremendous attention in the past fifteen years and are extensively investigated in various fields.Crystallinity and stability are two crucial features for practical applications.In general,these two features are contradictory for COFs formed via dynamic covalent chemistry(DCC).High thermodynamic reversibility is usually required to attain exceptional crystallinity of COFs,often resulting in limited stability.The first two reported COFs are based on the boroxine and boronate ester linkages,which are unstable in water and even in humid conditions.Therefore,many researchers doubt the stability of COFs for real applications.Actually,in these years,various novel linkages have been developed for the construction of COFs,and numerous newly synthesized COFs are robust towards strong acid/base and even some of them can resist the attack of strong oxidizing and reducing agents.In this review,we focus on the linkage chemistry of the COFs in terms of crystallinity and stability,further extending it to the investigation in the mechanisms of the crystal growth and the overall regulation of the contradiction between stability and crystallinity.The strategies for improving the crystallinity,including selecting building units,introducing non-covalent interactions and slowing nucleation and growth rate,are described in the third section,while the methodologies for increasing the stability from the viewpoints of chemical modification and non-covalent interactions are summarized in the fourth section.Finally,the challenges and perspectives are presented.展开更多
Nanoparticle photosensitizers possess technical advantages for photocatalytic reactions due to enhanced light harvesting and efficient charge transport.Here we report synthesis of semiconductor nanoparticles through c...Nanoparticle photosensitizers possess technical advantages for photocatalytic reactions due to enhanced light harvesting and efficient charge transport.Here we report synthesis of semiconductor nanoparticles through covalent coupling and assembly of metalloporphyrin with condensed carbon nitride.The resultant nanoparticles consist of light harvesting component from the condensed carbon nitride and photocatalytic sites from the metalloporphyrins.This synergetic particle system effectively initiates efficient charge separation and transport and exhibits excellent photocatalytic activity for CO2 reduction.The CO production rate can reach up to 57μmol/(g·h)with a selectivity of 79%over competing H2 evolution.Controlled experiments demonstrate that the combination of light harvesting with photocatalytic activity via covalent assembly is crucial for the high photocatalytic activity.Due to effective charge separation and transfer,the resultant nanoparticle photocatalysts show exceptional photo stability against photo-corrosion under light irradiation,enabling for long-term utilization.This research opens a new way for the development of stable,effective nanoparticle photocatalysts using naturally abundant porphyrin pigments.展开更多
Hydrogels are three-dimensional platforms that serve as substitutes for native extracellular matrix.These materials are starting to play important roles in regenerative medicine because of their similarities to native...Hydrogels are three-dimensional platforms that serve as substitutes for native extracellular matrix.These materials are starting to play important roles in regenerative medicine because of their similarities to native matrix in water content and flexibility.It would be very advantagoues for researchers to be able to regulate cell behavior and fate with specific hydrogels that have tunable mechanical properties as biophysical cues.Recent developments in dynamic chemistry have yielded designs of adaptable hydrogels that mimic dynamic nature of extracellular matrix.The current review provides a comprehensive overview for adaptable hydrogel in regenerative medicine as follows.First,we outline strategies to design adaptable hydrogel network with reversible linkages according to previous findings in supramolecular chemistry and dynamic covalent chemistry.Next,we describe the mechanism of dynamic mechanical microenvironment influence cell behaviors and fate,including how stress relaxation influences on cell behavior and how mechanosignals regulate matrix remodeling.Finally,we highlight techniques such as bioprinting which utilize adaptable hydrogel in regenerative medicine.We conclude by discussing the limitations and challenges for adaptable hydrogel,and we present perspectives for future studies.展开更多
In organic chemistry, as defined by Abegg, Kossel, Lewis and Langmuir, compounds are normally represented using structural formulas called Lewis structures. In these structures, the octet rule is used to define the nu...In organic chemistry, as defined by Abegg, Kossel, Lewis and Langmuir, compounds are normally represented using structural formulas called Lewis structures. In these structures, the octet rule is used to define the number of covalent bonds that each atom forms with its neighbors and multiple bonds are frequent. Lewis’ octet rule has unfortunately shown limitations very early when applied to non-organic compounds: most of them remain incompatible with the “rule of eight” and location of charges is uncertain. In an attempt to unify structural formulas of octet and non-octet molecules or single-charge ions, an even-odd rule was recently proposed, together with a procedure to locate charge precisely. This even-odd rule has introduced a charge-dependent effective-valence number calculated for each atom. With this number and the number of covalent bonds of each element, two even numbers are calculated. These numbers are both used to understand and draw structuralformulas of single-covalent-bonded compounds. In the present paper, a procedure is proposed to adjust structural formulas of compounds that are commonly represented with multiple bonds. In order to keep them compatible with the even-odd rule, they will be represented using only single covalent bonds. The procedure will then describe the consequences of bond simplification on charges locations. The newly obtained representations are compared to their conventional structural formulas, i.e. single-bond representation vs. multiple-bond structures. Throughout the comparison process, charges are precisely located and assigned to specific atoms. After discussion of particular cases of compounds, the paper finally concludes that a rule limiting representations of multiplecovalent bonds to single covalent bonds, seems to be suitable for numerous known compounds.展开更多
Integrating multiple functions into one gel that can be widely applied to electronic devices as well as chemical and biomedical engineering remains a big challenge.Here,a multifunctional ionic liquid/dynamic covalent ...Integrating multiple functions into one gel that can be widely applied to electronic devices as well as chemical and biomedical engineering remains a big challenge.Here,a multifunctional ionic liquid/dynamic covalent bonds (ionic/DCB) type gel was designed and synthesized via one-pot polymerization.With the assistance of electrostatic interaction provided by the imidazolium cations of IL and the reversible DCB of boronic ester,as-prepared ionic/DCB gel showed good stretchable properties and high ionic conductivity at ambient conditions.In addition,the electrostatic interaction between imidazolium cations and sulfonate anions and the reversible DCB led to enhanced chain mobility and thereby excellent self-healing properties.Particularly,sulfonate anions in ionic/DCB gel could alleviate the migration of electronegative polysulfide and promote the transportation of electropositive lithium ion in lithium-sulfur battery system.Therefore,this work provides a new insight to promote the current research on self-healing gels,hopefully expanding their applications in electronic devices.展开更多
Uranium extraction from seawater is of strategic significance for nuclear power generation.Amidoximebased functional adsorbents play indispensable roles in the recovery of seawater uranium with high efficiency.Neverth...Uranium extraction from seawater is of strategic significance for nuclear power generation.Amidoximebased functional adsorbents play indispensable roles in the recovery of seawater uranium with high efficiency.Nevertheless,balancing the adsorption capacity and selectivity is challenging in the presence of complicated interfering ions especially vanadium.Herein,a polyarylether-based covalent organic framework functionalized with open-chain amidoxime(COF-HHTF-AO)was synthesized with remarkable chemical stability and excellent crystallinity.Impressively,the adsorption capacity of COF-HHTF-AO towards uranium in natural seawater reached up to 5.12 mg/g,which is 1.61 times higher than that for vanadium.Detailed computational calculations revealed that the higher selectivity for uranium over vanadium originated from the specific bonding nature and coordination pattern with amidoxime.Combining enhanced adsorption capacity,excellent selectivity and ultrahigh stability,COF-HHTF-AO serves as a promising adsorbent for uranium extraction from the natural seawater.展开更多
In recent years,as a new class of two-dimensional polymer,covalent organic frameworks（COFs） have attracted intensive attention and developed rapidly.This review provides an overview of a type of COFs which can be ut...In recent years,as a new class of two-dimensional polymer,covalent organic frameworks（COFs） have attracted intensive attention and developed rapidly.This review provides an overview of a type of COFs which can be utilized as organic semiconductors.Carefully choosing monomers as the building blocks will bestow different types of semiconducting character on COFs.We summarize the p-type,n-type and ambipolar semiconducting COFs and highlight the effects of π-functional building blocks on the photoconductive behaviors of the semiconducting COFs.展开更多
文摘Supported noble metal nanoparticles （including nanoclusters） are widely used in many industrial catalytic processes. While the finely dispersed nanostructures are highly active, they are usually thermodynamically unstable and tend to aggregate or sinter at elevated temperatures. This scenario is particularly true for supported nanogold catalysts because the gold nanostructures are easily sintered at high temperatures, under reaction conditions, or even during storage at ambient temperature. Here, we demonstrate that isolated Au single atoms dispersed on iron oxide nanocrystallites （Aul/FeOx） are much more sintering- resistant than Au nanostructures, and exhibit extremely high reaction stability for CO oxidation in a wide temperature range. Theoretical studies revealed that the positively charged and surface-anchored Aul atoms with high valent states formed significant covalent metal-support interactions （CMSIs）, thus providing the ultra-stability and remarkable catalytic performance. This work may provide insights and a new avenue for fabricating supported Au catalysts with ultra-high stability.
文摘Graphene has attracted the interest of chemists, physicists, and materials scientists due to its extraordinary structural, mechanical, and electronic properties. While pristine graphene is desirable for applications that require a high electrical conductivity, many other applications require modified or functionalized forms of graphene, such as graphene oxide, reduced graphene, or other functionalized forms. Structurally modifying graphene through chemical functionalization reveals the numerous possibilities for tuning its structure; several chemical and physical functionalization methods have been explored to improve the stabilization and modification of graphene. In this review, we report recent progress towards the chemical modification of graphene, including both covalent and noncovalent methods, for use in various applications.
基金Financial support from NSFC(21836001)National Key Research and Development Program of China(2017YFA0207002 and 2018YFC1900105)+1 种基金Science Challenge Project(TZ2016004)Beijing Outstanding Young Scientist Program were greatly appreciated.
文摘Covalent organic frameworks(COFs)are a new type of crystalline porous polymers known for chemical stability,excellent structural regularity,robust framework,and inherent porosity,making them promising materials for capturing various types of pollutants from aqueous solutions.This review thoroughly presents the recent progress and advances of COFs and COF-based materials as superior adsorbents for the efficient removal of toxic heavy metal ions,radionuclides,and organic pollutants.Information about the interaction mechanisms between various pollutants and COF-based materials are summarized from the macroscopic and microscopic standpoints,including batch experiments,theoretical calculations,and advanced spectroscopy analysis.The adsorption properties of various COF-based materials are assessed and compared with other widely used adsorbents.Several commonly used strategies to enhance COF-based materials’adsorption performance and the relationship between structural property and sorption ability are also discussed.Finally,a summary and perspective on the opportunities and challenges of COFs and COF-based materials are proposed to provide some inspiring information on designing and fabricating COFs and COF-based materials for environmental pollution management.
文摘Base excision repair （BER） is an evolutionarily conserved process for maintaining genomic integrity by eliminating several dozen damaged （oxidized or aikylated） or inappropriate bases that are generated endogenously or induced by genotoxicants, predominantly, reactive oxygen species （ROS）. BER involves 4-5 steps starting with base excision by a DNA glycosylase, followed by a common pathway usually involving an AP-endonuclease （APE） to generate 3＇ OH terminus at the damage site, followed by repair synthesis with a DNA polymerase and nick sealing by a DNA iigase. This pathway is also responsible for repairing DNA single-strand breaks with blocked termini directly generated by ROS. Nearly all glycosylases, far fewer than their substrate lesions particularly for oxidized bases, have broad and overlapping substrate range, and could serve as back-up enzymes in vivo. In contrast, mammalian cells encode only one APE, APEI, unlike two APEs in lower organisms. In spite of overall similarity, BER with distinct subpathways in the mammals is more complex than in E. coli. The glycosylases form complexes with downstream proteins to carry out efficient repair via distinct subpathways one of which, responsible for repair of strand breaks with 3＇ phosphate termini generated by the NEIL family glycosylases or by ROS, requires the phosphatase activity of polynucleotide kinase instead of APE1. Different complexes may utilize distinct DNA polymerases and iigases. Mammalian glycosylases have nonconserved extensions at one of the termini, dispensable for enzymatic activity but needed for interaction with other BER and non-BER proteins for complex formation and organeile targeting. The mammalian enzymes are sometimes covalently modified which may affect activity and complex formation. The focus of this review is on the early steps in mammalian BER for oxidized damage.
基金supported by the National Natural Science Foundation of China (No. 21806083)the National Key R&D Program of China (No. 2018YFD0400703)+1 种基金the 111 Program of the Ministry of Education, China (No. T2017002)the Fundamental Research Funds for the Central Universities
文摘Environmental pollution is one of the most serious problems facing mankind today,and has attracted widespread attention worldwide. The burgeoning class of crystalline porous organic framework materials, metal–organic frameworks and covalent organic frameworks present promising application potential in areas related to pollution control due to their interesting surface properties. In this review, the literature of the past five years on the adsorptive removal of various hazardous materials, mainly including heavy metal ions, harmful gases, organic dyes, pharmaceutical and personal care products, and radionuclides from the environment by using COFs and MOFs, is summarized. The adsorption mechanisms are also discussed to help understand their adsorption performance and selectivity. Additionally, some insightful suggestions are given to enhance the performance of MOFs and COFs in the adsorptive removal of various hazardous materials.
基金This work was supported by the Natural Science Foundation of Shandong Province(No.ZR2020JQ19)Taishan Scholars Program of Shandong Province(Nos.tsqn201812002 and ts20190908)+3 种基金the National Natural Science Foundation of China(No.51972198)the Young Scholars Program of Shandong University(No.2016WLJH03)the State Key Program of National Natural Science of China(No.61633015),Shenzhen Fundamental Research Program(No.JCYJ20190807093405503)the Project of the Taishan Scholar(No.ts201511004).
文摘Lithium metal(Li)is believed to be the ultimate anode for lithium-ion batteries(LIBs)owing to the advantages of high theoretical capacity,the lowest electrochemical potential,and light weight.Nevertheless,issues such as uncontrollable growth of Li dendrites,large volume changes,high chemical reactivity,and unstable solid electrolyte interphase(SEI)hinder its rapid development and practical application.Herein a stable and dendrite-free Li-metal anode is obtained by designing a flexible and freestanding MXene/COF framework for metallic Li.COF-LZU1 microspheres are distributed among the MXene film framework.Lithiophilic COF-LZU1 microspheres as nucleation seeds can promote uniform Li nucleation by homogenizing the Li^(+)flux and lowering the nucleation barrier,finally resulting in dense and dendrite-free Li deposition.Under the regulation of the COF-LZU1 seeds,the Coulombic efficiency of the MXene/COF-LZU1 framework and electrochemical stability of corresponding symmetric cells are obviously enhanced.Li-S full cells with the modified Li-metal anode and sulfurized polyacrylonitrile(S@PAN)cathode also exhibited a superior electrochemical performance.
基金the National Natural Science Foundation of China(Nos.51673084,51473061)the JLU Cultivation Fund for the National Science Fund for Distinguished Young Scholars,for financial support
文摘Covalent organic frameworks（COFs） are an emerging class of porous covalent organic structures whose backbones were composed of light elements（B,C,N,O,Si） and linked by robust covalent bonds to endow such material with desirable properties,i.e.,inherent porosity,well-defined pore aperture,ordered channel structure,large surface area,high stability,and multi-dimension.As expected,the abovementioned properties of COFs broaden the applications of this class of materials in various fields such as gas storage and separation,catalysis,optoelectronics,sensing,small molecules adsorption,and drug delivery.In this review,we outlined the synthesis of COFs and highlighted their applications ranging from the initial gas storage and separation to drug delivery.
文摘Lewis developed a 2D-representation of molecules, charged or uncharged, known as structural formula, and stated the criteria to draw it. At the time, the vast majority of known molecules followed the octet-rule, one of Lewis’s criteria. The same method was however rapidly applied to represent compounds that do not follow the octet-rule, i.e. compounds for which some of the composing atoms have greater or less than eight electrons in their valence shell. In a previous paper, an even-odd rule was proposed and shown to apply to both types of uncharged molecules. In the present paper, the even-odd rule is extended with the objective to encompass all single-bonded ions in one group: Lewis’s ions, hypo- and hypervalent ions. The base of the even-odd representation is compatible with Lewis’s diagram. Additionally, each atom is subscripted with an even number calculated by adding the valence number, the number of covalent bonds of the element, and its electrical charge. This paper describes how to calculate the latter number and in doing so, how charge and electron-pairs can actually be precisely localized. Using ions known to be compatible with Lewis’s rule of eight, the even-odd rule is compared with the former. The even-odd rule is then applied to ions known as hypo- or hypervalent. An interesting side effect of the presented rule is that charge and electron-pairs are unambiguously assigned to one of the atoms composing the single-charged ion. Ions that follow the octet rule and ions that do not, are thus reconciled in one group called “electron-paired ions” due to the absence of unpaired electrons. A future paper will focus on the connection between the even-odd rule and molecules or ions having multiple bonds.
基金the 973 Program(No.2013CB834704)the National Natural Science Foundation of China(Nos.21471018,21201018,21404010)1000 Plan (Youth) for financial support
文摘Covalent organic frameworks（COFs） as an emerging class of porous materials have achieved remarkable progress in recent years.Their high surface area,low mass densities,highly ordered periodic structures,and ease of functionalization make COFs exhibit superior potential in gas storage and separation,optoelectronic device and catalysis.This mini review gives a brief introduction of COFs and highlights their applications in electronic and optical fields.
基金supported by the National Natural Science Foundation of China(21922502,21674012)Beijing Institute of Technology Research Fund Program。
文摘Covalent organic frameworks(COFs)are a class of organic porous polymers with high crystallinity,and their structures can be precisely tailored via topology design.Owing to the characteristics of permanent pores,periodic structures and rich building blocks,COFs have triggered tremendous attention in the past fifteen years and are extensively investigated in various fields.Crystallinity and stability are two crucial features for practical applications.In general,these two features are contradictory for COFs formed via dynamic covalent chemistry(DCC).High thermodynamic reversibility is usually required to attain exceptional crystallinity of COFs,often resulting in limited stability.The first two reported COFs are based on the boroxine and boronate ester linkages,which are unstable in water and even in humid conditions.Therefore,many researchers doubt the stability of COFs for real applications.Actually,in these years,various novel linkages have been developed for the construction of COFs,and numerous newly synthesized COFs are robust towards strong acid/base and even some of them can resist the attack of strong oxidizing and reducing agents.In this review,we focus on the linkage chemistry of the COFs in terms of crystallinity and stability,further extending it to the investigation in the mechanisms of the crystal growth and the overall regulation of the contradiction between stability and crystallinity.The strategies for improving the crystallinity,including selecting building units,introducing non-covalent interactions and slowing nucleation and growth rate,are described in the third section,while the methodologies for increasing the stability from the viewpoints of chemical modification and non-covalent interactions are summarized in the fourth section.Finally,the challenges and perspectives are presented.
基金E B.acknowledges the support from the National Natural Science Foundation of China(Nos.21771055 and U1604139)Zhongyuan high level talents special support plan(No.204200510010)Scientific and Technological Innovation Team in University of Henan Province(No.20IRTSTHN001).
文摘Nanoparticle photosensitizers possess technical advantages for photocatalytic reactions due to enhanced light harvesting and efficient charge transport.Here we report synthesis of semiconductor nanoparticles through covalent coupling and assembly of metalloporphyrin with condensed carbon nitride.The resultant nanoparticles consist of light harvesting component from the condensed carbon nitride and photocatalytic sites from the metalloporphyrins.This synergetic particle system effectively initiates efficient charge separation and transport and exhibits excellent photocatalytic activity for CO2 reduction.The CO production rate can reach up to 57μmol/(g·h)with a selectivity of 79%over competing H2 evolution.Controlled experiments demonstrate that the combination of light harvesting with photocatalytic activity via covalent assembly is crucial for the high photocatalytic activity.Due to effective charge separation and transfer,the resultant nanoparticle photocatalysts show exceptional photo stability against photo-corrosion under light irradiation,enabling for long-term utilization.This research opens a new way for the development of stable,effective nanoparticle photocatalysts using naturally abundant porphyrin pigments.
基金support of the National Key Research and Development Program of China(2016YFE0132700)National Natural Science Foundation of China(51822306,51673171)+1 种基金Science Technology Department of Zhejiang Province(2020C03042)the Fundamental Research Funds for the Central Universities of China.
文摘Hydrogels are three-dimensional platforms that serve as substitutes for native extracellular matrix.These materials are starting to play important roles in regenerative medicine because of their similarities to native matrix in water content and flexibility.It would be very advantagoues for researchers to be able to regulate cell behavior and fate with specific hydrogels that have tunable mechanical properties as biophysical cues.Recent developments in dynamic chemistry have yielded designs of adaptable hydrogels that mimic dynamic nature of extracellular matrix.The current review provides a comprehensive overview for adaptable hydrogel in regenerative medicine as follows.First,we outline strategies to design adaptable hydrogel network with reversible linkages according to previous findings in supramolecular chemistry and dynamic covalent chemistry.Next,we describe the mechanism of dynamic mechanical microenvironment influence cell behaviors and fate,including how stress relaxation influences on cell behavior and how mechanosignals regulate matrix remodeling.Finally,we highlight techniques such as bioprinting which utilize adaptable hydrogel in regenerative medicine.We conclude by discussing the limitations and challenges for adaptable hydrogel,and we present perspectives for future studies.
文摘In organic chemistry, as defined by Abegg, Kossel, Lewis and Langmuir, compounds are normally represented using structural formulas called Lewis structures. In these structures, the octet rule is used to define the number of covalent bonds that each atom forms with its neighbors and multiple bonds are frequent. Lewis’ octet rule has unfortunately shown limitations very early when applied to non-organic compounds: most of them remain incompatible with the “rule of eight” and location of charges is uncertain. In an attempt to unify structural formulas of octet and non-octet molecules or single-charge ions, an even-odd rule was recently proposed, together with a procedure to locate charge precisely. This even-odd rule has introduced a charge-dependent effective-valence number calculated for each atom. With this number and the number of covalent bonds of each element, two even numbers are calculated. These numbers are both used to understand and draw structuralformulas of single-covalent-bonded compounds. In the present paper, a procedure is proposed to adjust structural formulas of compounds that are commonly represented with multiple bonds. In order to keep them compatible with the even-odd rule, they will be represented using only single covalent bonds. The procedure will then describe the consequences of bond simplification on charges locations. The newly obtained representations are compared to their conventional structural formulas, i.e. single-bond representation vs. multiple-bond structures. Throughout the comparison process, charges are precisely located and assigned to specific atoms. After discussion of particular cases of compounds, the paper finally concludes that a rule limiting representations of multiplecovalent bonds to single covalent bonds, seems to be suitable for numerous known compounds.
基金financially supported by the National Natural Science Fund for Distinguished Young Scholars (No. 21425417)the National Natural Science Foundation of China (Nos. 21835005, U1862109, and 21704071)the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘Integrating multiple functions into one gel that can be widely applied to electronic devices as well as chemical and biomedical engineering remains a big challenge.Here,a multifunctional ionic liquid/dynamic covalent bonds (ionic/DCB) type gel was designed and synthesized via one-pot polymerization.With the assistance of electrostatic interaction provided by the imidazolium cations of IL and the reversible DCB of boronic ester,as-prepared ionic/DCB gel showed good stretchable properties and high ionic conductivity at ambient conditions.In addition,the electrostatic interaction between imidazolium cations and sulfonate anions and the reversible DCB led to enhanced chain mobility and thereby excellent self-healing properties.Particularly,sulfonate anions in ionic/DCB gel could alleviate the migration of electronegative polysulfide and promote the transportation of electropositive lithium ion in lithium-sulfur battery system.Therefore,this work provides a new insight to promote the current research on self-healing gels,hopefully expanding their applications in electronic devices.
基金supported by the Science Challenge Project(TZ2016004)the National Natural Key Research and Development Program of China(2018YFC1900105 and 2017YFA0207002)Beijing Outstanding Young Scientist Program。
文摘Uranium extraction from seawater is of strategic significance for nuclear power generation.Amidoximebased functional adsorbents play indispensable roles in the recovery of seawater uranium with high efficiency.Nevertheless,balancing the adsorption capacity and selectivity is challenging in the presence of complicated interfering ions especially vanadium.Herein,a polyarylether-based covalent organic framework functionalized with open-chain amidoxime(COF-HHTF-AO)was synthesized with remarkable chemical stability and excellent crystallinity.Impressively,the adsorption capacity of COF-HHTF-AO towards uranium in natural seawater reached up to 5.12 mg/g,which is 1.61 times higher than that for vanadium.Detailed computational calculations revealed that the higher selectivity for uranium over vanadium originated from the specific bonding nature and coordination pattern with amidoxime.Combining enhanced adsorption capacity,excellent selectivity and ultrahigh stability,COF-HHTF-AO serves as a promising adsorbent for uranium extraction from the natural seawater.
基金the support from National Program for Thousand Young Talents of Chinathe National Natural Science Foundation of China(No.21544001)Fudan University
文摘In recent years,as a new class of two-dimensional polymer,covalent organic frameworks（COFs） have attracted intensive attention and developed rapidly.This review provides an overview of a type of COFs which can be utilized as organic semiconductors.Carefully choosing monomers as the building blocks will bestow different types of semiconducting character on COFs.We summarize the p-type,n-type and ambipolar semiconducting COFs and highlight the effects of π-functional building blocks on the photoconductive behaviors of the semiconducting COFs.
