In this paper,the third-order nonlinear optical(NLO)properties of covalent organic framework(COF)materials with conjugated amphoteric ion structure are studied for the first time.A highly ordered crystalline ultrathin...In this paper,the third-order nonlinear optical(NLO)properties of covalent organic framework(COF)materials with conjugated amphoteric ion structure are studied for the first time.A highly ordered crystalline ultrathin films of the ionic COF material PySQ-iCOF was successfully fabricated using a solid-liquid interface method,meanwhile the building units extracted to be independent small molecule,1-PySA,were synthesized for comparative studies.Compared to 1-PySA,PySQ-iCOF possesses not only a larger conjugated system but also exhibits enhanced polarization and charge transfer capabilities.The NLO properties of PySQ-iCOF and the small molecule 1-PySA were investigated using Z-scan technique at a wavelength of 532 nm,revealing the PySQ-iCOF thin film exhibits outstanding NLO performance.Specifically,it demonstrates saturable absorption under nanosecond(ns)pulse laser irradiation(β=9.59×10^(-6) m/W),while exhibiting reverse saturable absorption under femtosecond(fs)pulse conditions(β=6.91×10^(-8) m/W).Furthermore,the PySQ-iCOF film exhibits strong negative refractive nonlinearity,−6×10^(-12) m^(2)/W for ns and -3.8×10^(-13) m^(2)/W for fs,respectively.Transient absorption spectroscopy studies indicate that the pulse-width-dependent nonlinear absorption char-acteristics of the PySQ-iCOF film originate from the generation of triplet excited states.Both nonlinear absorption coefficient and nonlinear refractive index of the PySQ-iCOF film surpass those of most reported organic materials measured under comparable conditions,which provides huge potential in all-optical manipulating and switching at the nanoscale as outstanding NLO materials.展开更多
Ultra-thin two-dimensional(2D)organic semiconductors are promising candidates for photocatalysts because of the short charge diffusion pathway and favorable exposure of active sites plus the versatile architecture.Non...Ultra-thin two-dimensional(2D)organic semiconductors are promising candidates for photocatalysts because of the short charge diffusion pathway and favorable exposure of active sites plus the versatile architecture.Nonetheless,the inherent dielectric confinement of 2D materials will induce a strong exciton effect hampering the charge separation.Herein,we demonstrated an effective way to reduce the dielectric confinement effect of 2D ionic covalent organic nanosheets(iCONs)by tailoring the functional group via molecular engineering.Three ultra-thin CONs with different functional groups and the same ionic moieties were synthesized through Schiff base condensation between ionic amino monomer triaminoguanidinium chloride(TG)and aldehyde linkers.The integration of the hydroxyl group was found to significantly increase the dielectric constant by enhancing the polarizability of ionic moieties,and thus reduced the dielectric confinement and the corresponding exciton binding energy(E_(b)).The champion hydroxyl-functional iCON exhibited promoted exciton dissociation and in turn a high photocatalytic hydrogen production rate under visible-light irradiation.This work provided insights into the rationalization of the dielectric confinement effect of low-dimensional photocatalysts.展开更多
The synthesis of ionic covalent organic frameworks(iCOFs)is considerably limited due to the low solubility and challenging synthesis of the required monomers,making the ionic conversion of neutral COFs via post-synthe...The synthesis of ionic covalent organic frameworks(iCOFs)is considerably limited due to the low solubility and challenging synthesis of the required monomers,making the ionic conversion of neutral COFs via post-synthetic modification(PSM)a viable alternative.Herein,we successfully converted a neutral COF(TfaTta)into a cationic COF(TfaTta-Br)through the Menshutkin reaction,utilizing benzyl bromide(BnBr)as the halogenated hydrocarbon,which subsequently underwent ion-exchange with the anionic compound methyl blue(MB)to generate a multifunctional material(TfaTta-MB)with dual emission.Studies demonstrated that TfaTta-MB is capable of ratiometric sensing of dicamba(DMA)and 2,6-dichloro-4-nitroaniline(DCN),two commonly used organochlorine pesticides,with limits of detection as low as 0.0241μM and 0.128μM,respectively.Density functional theory(DFT)calculations were performed for further research on the responsive mechanism.A hydrogel film(TfaTta-MB/AG)was prepared and affixed to a laboratory glove,creating a portable sensing device for detecting pesticide residues on the surface of vegetables.Notably,the obtained material enables colorimetric sensing of DMA and a smart sensing platform has been developed leveraging this functionality.In short,this work not only broadens the scope of ion transformation methods for neutral COFs,but also imposes great improvement in ratiometric sensing for organochlorine pesticide residues.展开更多
Calcium metal batteries(CMBs),utilizing calcium(Ca)as anodes,offer great potential for next-generation high-energy density battery technologies.However,Ca plating/stripping at room temperature(r.t.)is severely impeded...Calcium metal batteries(CMBs),utilizing calcium(Ca)as anodes,offer great potential for next-generation high-energy density battery technologies.However,Ca plating/stripping at room temperature(r.t.)is severely impeded by the formation of ion-insulating passivation layers.Constructing artificial protective layers that can effectively transport Ca^(2+)on Ca metal is crucial for realizing practical CMBs.Nonetheless,identifying a suitable candidate that is both highly ionic conductive(>10^(-4) S cm^(-1) at r.t.)and electrically insulating remains a formidable challenge.Ionic covalent organic frameworks(iCOFs)represent a distinctive class of porous,crystalline polymers containing ionic moieties to facilitate ion conduction in batteries.In this study,we introduce,for the first time,single-ion conductive sulfonate iCOFs with a Ca^(2+) transference number of 0.95 and ionic conductivity of 2.2310-4 S cm^(-1) at r.t.as artificial protective layers for the Ca metal anode.This iCOF protective layer promotes uniform Ca deposition and effective anticorrosion of modified anodes.As a result,full cells equipped with iCOF-protective Ca anodes and polyaniline cathodes demonstrated stable operation up to 75 cycles with high energy density.Our work facilitates the attainment of high-performance CMBs by the construction of iCOF protective layers.展开更多
基金the National Natural Science Foundation of China(22171076)Jing Li at the Technical Institute of Physics and Chemistry,Chinese Academy of Sciences(CAS),for his measurement of dynamic processes.
文摘In this paper,the third-order nonlinear optical(NLO)properties of covalent organic framework(COF)materials with conjugated amphoteric ion structure are studied for the first time.A highly ordered crystalline ultrathin films of the ionic COF material PySQ-iCOF was successfully fabricated using a solid-liquid interface method,meanwhile the building units extracted to be independent small molecule,1-PySA,were synthesized for comparative studies.Compared to 1-PySA,PySQ-iCOF possesses not only a larger conjugated system but also exhibits enhanced polarization and charge transfer capabilities.The NLO properties of PySQ-iCOF and the small molecule 1-PySA were investigated using Z-scan technique at a wavelength of 532 nm,revealing the PySQ-iCOF thin film exhibits outstanding NLO performance.Specifically,it demonstrates saturable absorption under nanosecond(ns)pulse laser irradiation(β=9.59×10^(-6) m/W),while exhibiting reverse saturable absorption under femtosecond(fs)pulse conditions(β=6.91×10^(-8) m/W).Furthermore,the PySQ-iCOF film exhibits strong negative refractive nonlinearity,−6×10^(-12) m^(2)/W for ns and -3.8×10^(-13) m^(2)/W for fs,respectively.Transient absorption spectroscopy studies indicate that the pulse-width-dependent nonlinear absorption char-acteristics of the PySQ-iCOF film originate from the generation of triplet excited states.Both nonlinear absorption coefficient and nonlinear refractive index of the PySQ-iCOF film surpass those of most reported organic materials measured under comparable conditions,which provides huge potential in all-optical manipulating and switching at the nanoscale as outstanding NLO materials.
基金the National Natural Science Foundation of China(22072065,22178162,22222806)the Distinguished Youth Foundation of Jiangsu Province(BK20220053)the Six Talent Peaks Project in Jiangsu Province(JNHB-035)。
文摘Ultra-thin two-dimensional(2D)organic semiconductors are promising candidates for photocatalysts because of the short charge diffusion pathway and favorable exposure of active sites plus the versatile architecture.Nonetheless,the inherent dielectric confinement of 2D materials will induce a strong exciton effect hampering the charge separation.Herein,we demonstrated an effective way to reduce the dielectric confinement effect of 2D ionic covalent organic nanosheets(iCONs)by tailoring the functional group via molecular engineering.Three ultra-thin CONs with different functional groups and the same ionic moieties were synthesized through Schiff base condensation between ionic amino monomer triaminoguanidinium chloride(TG)and aldehyde linkers.The integration of the hydroxyl group was found to significantly increase the dielectric constant by enhancing the polarizability of ionic moieties,and thus reduced the dielectric confinement and the corresponding exciton binding energy(E_(b)).The champion hydroxyl-functional iCON exhibited promoted exciton dissociation and in turn a high photocatalytic hydrogen production rate under visible-light irradiation.This work provided insights into the rationalization of the dielectric confinement effect of low-dimensional photocatalysts.
基金supported by the National Natural Science Foundation of China(22375150)the Developing Science Funds of Tongji University(1380219059).
文摘The synthesis of ionic covalent organic frameworks(iCOFs)is considerably limited due to the low solubility and challenging synthesis of the required monomers,making the ionic conversion of neutral COFs via post-synthetic modification(PSM)a viable alternative.Herein,we successfully converted a neutral COF(TfaTta)into a cationic COF(TfaTta-Br)through the Menshutkin reaction,utilizing benzyl bromide(BnBr)as the halogenated hydrocarbon,which subsequently underwent ion-exchange with the anionic compound methyl blue(MB)to generate a multifunctional material(TfaTta-MB)with dual emission.Studies demonstrated that TfaTta-MB is capable of ratiometric sensing of dicamba(DMA)and 2,6-dichloro-4-nitroaniline(DCN),two commonly used organochlorine pesticides,with limits of detection as low as 0.0241μM and 0.128μM,respectively.Density functional theory(DFT)calculations were performed for further research on the responsive mechanism.A hydrogel film(TfaTta-MB/AG)was prepared and affixed to a laboratory glove,creating a portable sensing device for detecting pesticide residues on the surface of vegetables.Notably,the obtained material enables colorimetric sensing of DMA and a smart sensing platform has been developed leveraging this functionality.In short,this work not only broadens the scope of ion transformation methods for neutral COFs,but also imposes great improvement in ratiometric sensing for organochlorine pesticide residues.
基金Research Grants Council of the Hong Kong SAR Government,Grant/Award Numbers:16306921,16306022,15305022,C6047-23GFShanghai Municipal Natural Science Foundation,Grant/Award Number:22ZR1433400Hong Kong Polytechnic University,G-UARH,Grant/Award Number:1-BBR0。
文摘Calcium metal batteries(CMBs),utilizing calcium(Ca)as anodes,offer great potential for next-generation high-energy density battery technologies.However,Ca plating/stripping at room temperature(r.t.)is severely impeded by the formation of ion-insulating passivation layers.Constructing artificial protective layers that can effectively transport Ca^(2+)on Ca metal is crucial for realizing practical CMBs.Nonetheless,identifying a suitable candidate that is both highly ionic conductive(>10^(-4) S cm^(-1) at r.t.)and electrically insulating remains a formidable challenge.Ionic covalent organic frameworks(iCOFs)represent a distinctive class of porous,crystalline polymers containing ionic moieties to facilitate ion conduction in batteries.In this study,we introduce,for the first time,single-ion conductive sulfonate iCOFs with a Ca^(2+) transference number of 0.95 and ionic conductivity of 2.2310-4 S cm^(-1) at r.t.as artificial protective layers for the Ca metal anode.This iCOF protective layer promotes uniform Ca deposition and effective anticorrosion of modified anodes.As a result,full cells equipped with iCOF-protective Ca anodes and polyaniline cathodes demonstrated stable operation up to 75 cycles with high energy density.Our work facilitates the attainment of high-performance CMBs by the construction of iCOF protective layers.
