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
During the utilization of structural and functional advantages of polyoxometalates(POMs)for enhanced applications,a suitable assembly of these clusters in framework materials to act as binding nodes represents a promi...During the utilization of structural and functional advantages of polyoxometalates(POMs)for enhanced applications,a suitable assembly of these clusters in framework materials to act as binding nodes represents a promising approach.In contrast to well-developed coordination/covalent combinations,we have developed a convenient strategy to build porous structures of POMs with smaller-sized counterions as bridging ligands via ionic interactions to reinforce their capability in gas adsorption in parallel to metal-organic frameworks(MOFs)/covalent organic frameworks(COFs).With this goal,a series of POMs-based ionic frameworks(IFs)were constructed with triol-ligand modified Anderson-Evans-type clusters as building blocks,and their sodium counter-cations were used as linkers.The three-dimensional(3D)open-frameworks obtained displayed unusually selective CO_(2) capturing capability and efficient separation from their N_(2),H_(2),and CH_(4) mixtures under low pressure at room temperature.Among the synthesized IFs,the cobalt-centered cluster exhibited the best performance for the uptake and selective separation of CO_(2) over N_(2) and CH_(4) in a range of 0-1 bar,while the nickel-centered cluster displayed the highest selectivity over H_(2) at 1 bar.Breakthrough experiments based on real binary gas mixtures demonstrated that the cobalt-containing framework illustrated high performance in the actual gas separation and sustained stability against a simulated operating environment.展开更多
Elasticity,as an emerging phenomenon of crystals,endows the newfangled properties on crystals owing to the altered local crystallinity in the deformed state,and hence attracts increasing research endeavors.However,onl...Elasticity,as an emerging phenomenon of crystals,endows the newfangled properties on crystals owing to the altered local crystallinity in the deformed state,and hence attracts increasing research endeavors.However,only a few molecular crystals and a limited number of one-dimensional coordination polymer crystals have exhibited such fantastic elastic response under mechanical stress.Herein,we report the first example of elastic hydrogen-bonded ionic framework(HIF)of{(CN_(3)H_(6))_(2)[Ti(μ_(2)-O)(SO_(4))_(2)]}n,assembled from one-dimensional negatively charged inorganic[Ti(μ_(2)-O)(SO_(4))_(2)]n 2n-chains and positively charged organic guanidinium cations via hydrogen bonds and electrostatic interactions.The slender prismatic single crystal exhibits remarkable elasticity with an optimal elastic bending strain(ε)of 2.5%.Impressively,the crystals give rise to two-dimensional elasticity owing to the equivalent crystallographic planes of the exposed faces and an unusual elastic response at liquid nitrogen temperature.The in-depth crystallographic analyses reveal hydrogen bonds and electrostatic interactions between anion chains and cations function like adhesive glue and account for such specific elastic properties,owing to the flexible and dynamic attributes of hydrogen bonds as they can work in a range of distance and orientation.And the channel in HIF provides space for bending with reduced strain.Incorporating these factors into low-dimensional crystals could be a general guidance for designing elastic crystals.Elasticity ganged with other intrinsic properties of HIF materials could inspire their newfangled applications in the near future.展开更多
CO_(2) capture is one of the key technologies for dealing with the global warming and implementing lowcarbon development strategy.The emergence of ionic metal-organic frameworks(I-MOFs)has diversified the field of por...CO_(2) capture is one of the key technologies for dealing with the global warming and implementing lowcarbon development strategy.The emergence of ionic metal-organic frameworks(I-MOFs)has diversified the field of porous materials,which have been extensively applied for gas adsorption and separation.In this work,amino-functionalized imidazolium ionic liquid as organic monodentate ligand was used for one step synthesis microporous Cu based I-MOFs.Precise tuning of the adsorption properties was obtained by incorporating aromatic anions,such as phenoxy,benzene carboxyl,and benzene sulfonic acid group into the I-MOFs via a facile ion exchange method.The new I-MOFs showed high thermal stability and high capacity of 5.4 mmol·g^(-1) under atmospheric conditions for selective adsorption of CO_(2).The active sites of microporous Cu-MOF are the ion basic center and unsaturated metal,and electrostatic attraction and hydroxyl bonding between CO_(2) and modified functional sulfonic groups are responsible for the adsorption.This work provides a feasible strategy for the design of I-MOF for functional gas capture.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
A POMs-based 3D zeolike ionic crystal 1, {[Co（dpdo）2（CH3CN）（H2O）2]2（SiMo12O40）- （HEO）2}n （dpdo = 4,4＇-bipyridine-N,N＇-dioxide）, was constructed via self-assembly by embedding Keggintype [SiMo12O40]^4- po...A POMs-based 3D zeolike ionic crystal 1, {[Co（dpdo）2（CH3CN）（H2O）2]2（SiMo12O40）- （HEO）2}n （dpdo = 4,4＇-bipyridine-N,N＇-dioxide）, was constructed via self-assembly by embedding Keggintype [SiMo12O40]^4- polyanions within the intercrystalline voids as pillars and structurally characterized. The crystal structure was determined by single-crystal X-ray diffraction. The crystal is of triclinic, space group P1 with a = 11.430（3）, b = 12.242（3）, c = 14.279（3）A, α = 106.196（4）,β = 94.316（4）, γ = 98.294（3）°, V = 1884.5（7）A^3 Z = 1, C44H50N10O54CoEMo12Si, Mr = 2880.17, Dc = 2.538 g/cm^3, p = 2.484 mm^-1,F（000） = 1388, the final R = 0.0383 and wR = 0.1096 for 7753 observed reflections with I 〉 2σ（I）. Flack factor is 0.22（3）. Compound 1 is a pillar-layered framework with the [SiMo12O40]^4- anions linearly located on the square voids between the 2D bilayers which are formed by the dpdo ligands and cobalt（II） ions.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National Natural Science Foundation of China(no.21574057)the Assembly and Functionalities of Supramolecular Systems(AFSS no.:BP0618011)+1 种基金the Program for JLU Science,the Technology Innovative Research Team(no.2017TD-10)the 111 Project(no.D18012),and the Project of Educational Commission of Jilin Province of China(no.JJKH20190116KJ)for their financial support.
文摘During the utilization of structural and functional advantages of polyoxometalates(POMs)for enhanced applications,a suitable assembly of these clusters in framework materials to act as binding nodes represents a promising approach.In contrast to well-developed coordination/covalent combinations,we have developed a convenient strategy to build porous structures of POMs with smaller-sized counterions as bridging ligands via ionic interactions to reinforce their capability in gas adsorption in parallel to metal-organic frameworks(MOFs)/covalent organic frameworks(COFs).With this goal,a series of POMs-based ionic frameworks(IFs)were constructed with triol-ligand modified Anderson-Evans-type clusters as building blocks,and their sodium counter-cations were used as linkers.The three-dimensional(3D)open-frameworks obtained displayed unusually selective CO_(2) capturing capability and efficient separation from their N_(2),H_(2),and CH_(4) mixtures under low pressure at room temperature.Among the synthesized IFs,the cobalt-centered cluster exhibited the best performance for the uptake and selective separation of CO_(2) over N_(2) and CH_(4) in a range of 0-1 bar,while the nickel-centered cluster displayed the highest selectivity over H_(2) at 1 bar.Breakthrough experiments based on real binary gas mixtures demonstrated that the cobalt-containing framework illustrated high performance in the actual gas separation and sustained stability against a simulated operating environment.
基金We acknowledge support from the Chinese Academy of Sciences and University of Science and Technology of China,the National Key Research and Development Program of China(No.2021YFA1500402)the National Natural Science Foundation of China(Nos.21571167,51502282,and 22075266)the Fundamental Research Funds for the Central Universities(Nos.WK2060190053 and WK2060190100).
文摘Elasticity,as an emerging phenomenon of crystals,endows the newfangled properties on crystals owing to the altered local crystallinity in the deformed state,and hence attracts increasing research endeavors.However,only a few molecular crystals and a limited number of one-dimensional coordination polymer crystals have exhibited such fantastic elastic response under mechanical stress.Herein,we report the first example of elastic hydrogen-bonded ionic framework(HIF)of{(CN_(3)H_(6))_(2)[Ti(μ_(2)-O)(SO_(4))_(2)]}n,assembled from one-dimensional negatively charged inorganic[Ti(μ_(2)-O)(SO_(4))_(2)]n 2n-chains and positively charged organic guanidinium cations via hydrogen bonds and electrostatic interactions.The slender prismatic single crystal exhibits remarkable elasticity with an optimal elastic bending strain(ε)of 2.5%.Impressively,the crystals give rise to two-dimensional elasticity owing to the equivalent crystallographic planes of the exposed faces and an unusual elastic response at liquid nitrogen temperature.The in-depth crystallographic analyses reveal hydrogen bonds and electrostatic interactions between anion chains and cations function like adhesive glue and account for such specific elastic properties,owing to the flexible and dynamic attributes of hydrogen bonds as they can work in a range of distance and orientation.And the channel in HIF provides space for bending with reduced strain.Incorporating these factors into low-dimensional crystals could be a general guidance for designing elastic crystals.Elasticity ganged with other intrinsic properties of HIF materials could inspire their newfangled applications in the near future.
基金supported by the National Natural Science Foundation of China(Grant No.22272125)Knowledge Innovation Program of Wuhan-Basic Research(Grant No.2022020801010354)+1 种基金Shanxi-Zheda Institute of Advanced Materials and Chemical Engineering(Grant No.2022SX-TD015)Joint Fund of the Yulin University and the Dalian National Laboratory for Clean Energy(Grant No.YLU-DNL Fund 2021021)。
文摘CO_(2) capture is one of the key technologies for dealing with the global warming and implementing lowcarbon development strategy.The emergence of ionic metal-organic frameworks(I-MOFs)has diversified the field of porous materials,which have been extensively applied for gas adsorption and separation.In this work,amino-functionalized imidazolium ionic liquid as organic monodentate ligand was used for one step synthesis microporous Cu based I-MOFs.Precise tuning of the adsorption properties was obtained by incorporating aromatic anions,such as phenoxy,benzene carboxyl,and benzene sulfonic acid group into the I-MOFs via a facile ion exchange method.The new I-MOFs showed high thermal stability and high capacity of 5.4 mmol·g^(-1) under atmospheric conditions for selective adsorption of CO_(2).The active sites of microporous Cu-MOF are the ion basic center and unsaturated metal,and electrostatic attraction and hydroxyl bonding between CO_(2) and modified functional sulfonic groups are responsible for the adsorption.This work provides a feasible strategy for the design of I-MOF for functional gas capture.
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 Natural Science Foundation of Henan Province
文摘A POMs-based 3D zeolike ionic crystal 1, {[Co（dpdo）2（CH3CN）（H2O）2]2（SiMo12O40）- （HEO）2}n （dpdo = 4,4＇-bipyridine-N,N＇-dioxide）, was constructed via self-assembly by embedding Keggintype [SiMo12O40]^4- polyanions within the intercrystalline voids as pillars and structurally characterized. The crystal structure was determined by single-crystal X-ray diffraction. The crystal is of triclinic, space group P1 with a = 11.430（3）, b = 12.242（3）, c = 14.279（3）A, α = 106.196（4）,β = 94.316（4）, γ = 98.294（3）°, V = 1884.5（7）A^3 Z = 1, C44H50N10O54CoEMo12Si, Mr = 2880.17, Dc = 2.538 g/cm^3, p = 2.484 mm^-1,F（000） = 1388, the final R = 0.0383 and wR = 0.1096 for 7753 observed reflections with I 〉 2σ（I）. Flack factor is 0.22（3）. Compound 1 is a pillar-layered framework with the [SiMo12O40]^4- anions linearly located on the square voids between the 2D bilayers which are formed by the dpdo ligands and cobalt（II） ions.
