The traditional high-temperature preparation process of polyimide can cause many problems and limits the wider application in extreme conditions.An important challenge to be solved urgently is the reduction of imidiza...The traditional high-temperature preparation process of polyimide can cause many problems and limits the wider application in extreme conditions.An important challenge to be solved urgently is the reduction of imidization temperature.In this work,twelve kinds of polyimide films with different chain rigidity were prepared at low temperature of 200℃,in the absence or presence of imidazole used as the catalyst.The molecular rigidity and free volume were theoretically calculated,and relationship between structure and properties were systematically studied.The results show that imidization reaction under low temperatures is significantly affected by the rigidity of molecula r chains.The rigid structure of polyimide is not conducive to the low-temperature imidization,but this adverse effect can be eliminated by adding catalyst,resulting the notably increased imidization degree.The optical and thermal properties can be improved to a certain extent for the chemically catalyzed system,resulting in relatively higher heat resistance and thermal stability.While the mechanical performance could be determined by com plicating factors,greatly different from polyimide films prepa red by high temperature method.To investigate aggregation structures of film s,the effect of chain rigidity and catalyst on the stacking or orientation of molecular chains was further elaborated.This wo rk can contribute to the understanding of chemically catalyzed imidization that is rarely reported in the existing research,and will provide guidance for the low-temperature preparation of high-performance polyimides.展开更多
In this study, polyimide fibers at different stages of imidization were characterized by TGA, DSC, and FTIR. The imidization degree （ID） calculated by TGA was based on the weight loss of each sample, which was cause...In this study, polyimide fibers at different stages of imidization were characterized by TGA, DSC, and FTIR. The imidization degree （ID） calculated by TGA was based on the weight loss of each sample, which was caused by the imidization of residual amic acid groups. The results of TGA showed good regularity with the thermal treatment temperature of the PI fibers. For DSC, the ID was calculated based on the area of endothermal peak of each sample. Compared with TGA, DSC showed a relatively higher value because the endothermal peak was reduced by the exothermic re-formation of polyamic acid which may be partially degraded during thermal treatment. The IDs obtained by the FTIR spectra generally showed poorer regularities than those obtained by both TGA and DSC, especially for the results calculated using the 730 cm^-1 band. Based on the 1350 cm^-1 band, the obtained IDs showed better agreement with the TGA or DSC results. The results obtained by these three methods were compared and analyzed. The ID obtained by TGA showed much more reliability among these three methods.展开更多
In order to lower the imidization temperature of polyamic acids（PAA）, the catalytic activities of the curing agents p-hydroxybenzoic acid（PHA）, quinoline（QL）, benzimidazole（BI）, benzotriazole（BTA）, triethyla...In order to lower the imidization temperature of polyamic acids（PAA）, the catalytic activities of the curing agents p-hydroxybenzoic acid（PHA）, quinoline（QL）, benzimidazole（BI）, benzotriazole（BTA）, triethylamine（Et_3N） and 1, 8-diazabicyclo [5.4.0]undec-7-ene（DBU） were investigated in the process of thermal imidization of PAA. In addition, the effect of these various curing agents on the thermal stabilities and mechanical properties of the resultant polyimide（PI） films was determined. Quinoline was found to be an effective curing accelerator in the use of two-step method for synthesizing PI. Due to its moderate base strength, low steric crowding effect and moderate boiling point, quinoline could not only accelerate PAA to achieve imidization completely at 180 ℃, but also maintain the mechanical properties and thermal stability of the ordinary PI film. Any residual quinoline could be removed from PI films by heating at 250 ℃ for 4 h.展开更多
2-substituted-1-amino-o-carboranes 2-R-1-NH_(2)-o-C_(2)B_(10)H_(10)(R=CH_(3),1a;R=Ph,1b)were synthesized and the reactions of these compounds with the yttrium dialkyl complex[Y(L)(CH_(2)SiMe3)_(2)](L=[2-(2,5-Me_(2)C_(...2-substituted-1-amino-o-carboranes 2-R-1-NH_(2)-o-C_(2)B_(10)H_(10)(R=CH_(3),1a;R=Ph,1b)were synthesized and the reactions of these compounds with the yttrium dialkyl complex[Y(L)(CH_(2)SiMe3)_(2)](L=[2-(2,5-Me_(2)C_(4)H_(2)N)C_(6)H4NC(Ph)=NDipp]-,Dipp=2,6-iPr_(2)C_(6)H_(3))were investigated.The 1H NMR spectroscopy indicate that the reaction of ytrrium dialkyl complex with one equivalent of 2-R-1-NH_(2)-o-C_(2)B_(10)H_(10) produce the mixture of ytrrium alkyl-amido complex[Y(L)(2-R-1-NH-o-C_(2)B_(10)H_(10))(CH_(2)SiMe3)](R=CH_(3),2a;R=Ph,2b)and bis(amido)complex[Y(L)(2-R-1-NH-o-C_(2)B_(10)H_(10))_(2)](R=CH_(3),3a;R=Ph,3b).The yttrium bridging imido complex[Y(L)(2-CH_(3)-1-N-o-C_(2)B_(10)H_(10))]_(2)(4a)was obtained by heating the mixture at 55℃for 12 h.Complex 3a was isolated and characterized by treating the yttrium dialkyl complex with two equivalents of 1a.The structures of complexes 3a and 4a were verified by single-crystal Xray diffraction.CCDC:2424136,3a;2424137,4a.展开更多
Glycosyl imidates are among the pioneering donors for catalytic glycosylation.We report a new generation of imidates featuring the presence of a pentafluorophenyl group,introduced via substitution on imidoyl fluoride ...Glycosyl imidates are among the pioneering donors for catalytic glycosylation.We report a new generation of imidates featuring the presence of a pentafluorophenyl group,introduced via substitution on imidoyl fluoride which is easily prepared,stable and user-friendly.The resulting donors exhibit exceptional shelf stability while can be readily activated to achieve high-yielding glycosylation,encompassing comprehensively aldosyl,ketosyl and ulosonyl donors,and both O-and N-glycosylation acceptors.Notably,the reactivity gradient across different generations of imidates,coupled with the accessible imidate acceptor from selective reaction of imidoyl fluoride at the anomeric hydroxyl group,enables a fully catalytic one-pot synthesis of oligosaccharides.展开更多
The major challenge in photocatalytic water splitting lies in water oxidation reactions,which still suffer from poor charge separation.This study overcame inefficient charge separation by establishing a robust interfa...The major challenge in photocatalytic water splitting lies in water oxidation reactions,which still suffer from poor charge separation.This study overcame inefficient charge separation by establishing a robust interfacial electric field through the electrostatic-driven assembly of Co_(3)O_(4) nanoparticles with a perylene imide supramolecule(PDINH).The well-aligned band structures and intimate interfacial contact in the PDINH/Co_(3)O_(4) heterostructure create an enhanced interfacial electric field that is 4.1-and 53.2-fold stronger than those of individual PDINH and Co_(3)O_(4),thus promoting directional charge separation and transfer.Moreover,S-scheme charge transfer strongly preserves the oxidative holes in PDINH to drive efficient water oxidation reactions.Consequently,PDINH/Co_(3)O_(4) composite achieves a photocatalytic oxygen evolution rate of 29.26 mmol g^(–1) h^(–1) under visible light irradiation,8.2-fold improvement over pristine PDINH,with an apparent quantum yield of 6.66%at 420 nm.This study provides fundamental insights into interfacial electric field control for the development of high-performance organic photocatalysts for efficient water oxidation.展开更多
Polymeric carbon nitride(PCN)has garnered increasing attention as a metal-free photocatalyst with a suitable band gap.In efforts to enhance its photocatalytic performance,researchers have examined various PCN material...Polymeric carbon nitride(PCN)has garnered increasing attention as a metal-free photocatalyst with a suitable band gap.In efforts to enhance its photocatalytic performance,researchers have examined various PCN materials,including poly(heptazine imide)(PHI)and poly(triazine imide)(PTI),two isomers within the PCN family that exhibit distinct and superior photocatalytic activity compared to other forms.The challenge,however,lies in the common practice among researchers to categorize PHI and PTI along with other PCN types under the overarching term“g-C_(3)N_(4),”which significantly impedes optimization efforts.The objective of this review is to provide comprehensive insights into the structural features,photoelectrochemical properties,and effective characterization methods employed for distinguishing between PHI and PTI materials.The review also summarizes various optimization strategies,such as crystallinity adjustments,defect engineering,morphology control,constructing heterojunction,and atomic-level metal loading dispersion,to elevate the photocatalytic activity of PHI and PTI,in addition to summarizing the history of carbon nitride development.Furthermore,this review highlights the primary applications of PHI and PTI,encompassing nitrogen fixation,biomass conversion,organic synthesis,CO_(2)reduction,pollutant degradation,H_(2)O_(2)production,and photocatalytic water splitting.Lastly,the prospects and challenges associated with further advancing PHI and PTI are thoroughly examined.展开更多
Poly(triazine imide),as a kind of highly crystalline g-C_(3)N_(4),exhibits a promising potential for photo-catalytic hydrogen production,however,some drawbacks still limit its photocatalytic performance.The strategy o...Poly(triazine imide),as a kind of highly crystalline g-C_(3)N_(4),exhibits a promising potential for photo-catalytic hydrogen production,however,some drawbacks still limit its photocatalytic performance.The strategy of constructing S-scheme heterojunction with different semiconductor photocatalysts enables the effective separation of photogenerated electrons and holes,and the strong oxidative and reductive properties of the original photocatalysts could be retained,which will significantly improve the photo-catalytic activity.In this work,we synthesized the organic-organic S-scheme heterojunction between PTI and organic small molecule poly(barbituric acid)(PBA)by hydrogen bond self-assembly method,which results in a significant enhancement of photocatalytic H_(2)production activity.The H_(2)production rate of the optimum PBA/PTI-2 sample under visible light irradiation is about 0.92 mmol g^(-1),which is 5.5 times higher than that of PTI and 14.4 times higher than that of PBA.This excellent photocatalytic performance is attributed to the successful construction of S-scheme heterojunction between PTI and PBA,which ef-fectively accelerates carrier transport and spatial segregation by the formation of a built-in electric field and band bending at the interface.In addition,the S-scheme heterojunction could also reserve the maxi-mum redox capability and enhance the light absorption of the prepared photocatalytic system.This work provides a new strategy and understanding for the design and development of organic-organic S-scheme heterojunction photocatalysts.展开更多
In order to achieve a wider range of ionizing radiations detection,novel fluorescence sensing materials have been developed that utilize the fluorescence enhancement phenomenon caused by the intramolecular photoinduce...In order to achieve a wider range of ionizing radiations detection,novel fluorescence sensing materials have been developed that utilize the fluorescence enhancement phenomenon caused by the intramolecular photoinduced electron transfer(PET)effect.Two perylene diimide isomers PDI-P and PDI-B were designed and synthesized,and their molecular structures were characterized by high-resolution Fourier transform mass spectrometry(HRMS),nuclear magnetic resonance hydrogen and carbon spectroscopy(~1H and~(13)C NMR).The interaction between ionizing radiation and fluorescent molecules was simulated by HCl titration.The results show that combining PDIs and HCl can improve fluorescence through the retro-PET process.Despite the similarities in chemical structures,the fluorescent enhancement multiple of PDI-B with aromatic amine as electron donor is much higher than that of PDI-P with alkyl amine.In the direct irradiation experiments of ionizing radiation,the emission enhancement multiples of PDI-P and PDI-B are 2.01 and 45.4,respectively.Furthermore,density functional theory(DFT)and time-dependent density functional theory(TDDFT)calculations indicate that the HOMO and HOMO-1 energy ranges of PDI-P and PDI-B are 0.54 e V and 1.13 e V,respectively.A wider energy range has a stronger driving force on electrons,which is conducive to fluorescence quenching.Both femtosecond transient absorption spectroscopy(fs-TAS)and transient fluorescence spectroscopy(TFS)tests show that PDI-B has shorter charge separation lifetime and higher electron transfer rate constant.Although both isomers can significantly reduce LOD during PET process,PDI-B with aromatic amine has a wider detection range of 0.118—240 Gy due to its larger emission enhancement,which is a leap of three orders of magnitude.It breaks through the detection range of gamma radiation reported in existing studies,and provides theoretical support for the further study of sensitive and effective new materials for ionizing radiation detection.展开更多
The notorious growth of zinc dendrite and the water-induced corrosion of zinc metal anodes(ZMAs)restrict the practical development of aqueous zinc ion batteries(AZIBs).In this work,a zinc metallized,imide-pillared cov...The notorious growth of zinc dendrite and the water-induced corrosion of zinc metal anodes(ZMAs)restrict the practical development of aqueous zinc ion batteries(AZIBs).In this work,a zinc metallized,imide-pillared covalent organic framework(ZPC)protective film has been engineered as a stable Zn^(2+)ion-conducting interphase to modulate interfacial kinetics and suppress side reactions for ZMAs.Compared to bare Zn,ZPC@Zn exhibits a higher Zn^(2+)ionic conductivity,a larger Zn^(2+)transference number,a lower electronic conductivity,a smaller desolvation activation energy and correspondingly a significant suppression of corrosion,hydrogen evolution and Zn dendrites.Impressively,the ZPC@Zn||ZPC@Zn symmetric cell obtains a cycling lifespan over 3000 h under 5 mA cm^(-2)for 1 mA h cm^(-2).The ZPC@Zn||NH_(4)V_(4)O_(10)coin-type full battery delivers a specific capacity of 195.8 mA h g^(-1)with a retention rate of78.5%at 2 A g^(-1)after 1100 cycles,and the ZPC@Zn||NH_(4)V_(4)O_(10) pouch full cell shows a retention of70.1%in reversible capacity at 3 A g^(-1)after 1100 cycles.The present incorporation of imide-linked covalent organic frameworks in the surface modification of ZMAs will offer fresh perspectives in the search for ideal protective films for the practicality of AZIBs.展开更多
The evolution of high-frequency communication has accentuated the significance of controlling dielectric properties in polymer media.Traditionally,it has been theorized that rigid molecular chains lead to lower dielec...The evolution of high-frequency communication has accentuated the significance of controlling dielectric properties in polymer media.Traditionally,it has been theorized that rigid molecular chains lead to lower dielectric loss.However,the validity of this proposition at high frequencies remains uncertain.To scrutinize the correlation between chain flexibility and dielectric properties,we synthesized six poly(ester imide)s(PEIs)with systematically varied molecular chain flexibilities by modifying the ester's substitution on the aromatic ring.The introduction of ester bonds bestowed all PEI films with a low dielectric dissipation factor(D_(f)),ranging from 0.0021 to 0.0038 at 10 GHz in dry conditions.The dry D_(f)displayed a pattern consistent with volume polarizability(P/V).Unexpectedly,PI-mmm-T,featu ring the most flexible molecular chain,exhibited the lowest dielectric loss under both dry(0.0021@10 GHz)and hygroscopic(0.0029@10 GHz)conditions.Furthermore,the observed increase in D_(f)after humidity absorption suggests that the high dielectric loss of PEI in applications may be attributed to its hygroscopic nature.Molecular simulations and characterization of the aggregation structure revealed that the smaller cavities within flexible molecular chains,after close stacking,impede the entry of water molecules.Despite sacrificing high-temperature resistance,the precursor exhibited enhanced solubility properties and could be processed into high-quality films.Our research unveils new insights into the relationship between flexibility and highfrequency dielectric loss,offering innovative perspectives on synthesizing aromatic polymers with exceptional dielectric properties.展开更多
The thermal and mechanical properties of the chemically imidized polyimide(CIPI) films and thermally imidized polyimide(TIPI) films were investigated systematically. Experimental results indicated that the CIPI films ...The thermal and mechanical properties of the chemically imidized polyimide(CIPI) films and thermally imidized polyimide(TIPI) films were investigated systematically. Experimental results indicated that the CIPI films show dramatically enhanced tensile strength and modulus with obviously reduced coefficient of thermal expansion(CTE) in comparison with TIPI films. These enhancements results from the high in-plane orientation and close packing of the CIPI backbones. Compared with thermal imidization which starts at about 140 °C, the chemical imidization activated by acetic anhydride and isoquinoline initiates the cyclization even at room temperature.The resulting imide rings restrict the mobility of polymer chains and lead to the in-plane orientation with solvent evaporation.Additionally, fewer small molecules remain in the films after treated at 120 °C by chemical imidization than by thermal imidization. The polymer chain plasticization caused by the evaporation of small molecules at high temperature is obviously restricted. Moreover, the partially imidized polymer inhibits the decomposition of mainchains that occurs at subsequent high temperature process, being beneficial to the formation of high molecular weight PI films. Hence, chemical imidization pathway shows apparent advantage to produce PI films with great combined properties, including high modulus, strength and toughness, as well as high thermal dimension stability etc.展开更多
N-Methyl-N-propylpiperidiniumbis（trifluoromethanesulfonyl）imide （PP13TFSI）, bis（triflu- oromethanesulfonyl）imide lithium salt （LiTFSI）, and poly（vinylidene difluoride-co- hexafluoropropylene） （P（VdF-HFP）...N-Methyl-N-propylpiperidiniumbis（trifluoromethanesulfonyl）imide （PP13TFSI）, bis（triflu- oromethanesulfonyl）imide lithium salt （LiTFSI）, and poly（vinylidene difluoride-co- hexafluoropropylene） （P（VdF-HFP）） were mixed and made into ionic liquid gel polymer electrolytes （ILGPEs） by solution casting. The morphology of ILGPEs was observed by scanning electron microscopy. It was found that the ILGPE had a loosened structure with liquid phase uniformly distributed. The ionic conductivity, lithium ion transference num- bet and electrochemical window were measured by electrochemical impedance spectroscopy, chronoamperometric and linear sweep voltammetry. The ionic conductivity and lithium ion transference number of this ILGPE reached 0.79 mS/cm and 0.71 at room temperature, and the electrochemical window was 0 to 5.1 V vs. Li＋/Li. Battery tests indicated that the ILGPE is stable when being operated in Li/LiFePO4 batteries. The discharge capacity maintained at about 135, 117, and 100 mAh/g at 30, 75, and 150 mA/g rates, respectively. The capacity retentions were almost 100% after 100 cycles without little capacity fading.展开更多
Nowadays,lithium-ion capacitors(LICs) have become a type of important electrochemical energy storage devices due to their high power and long cycle life characteristics with fast response time.As one of the essential ...Nowadays,lithium-ion capacitors(LICs) have become a type of important electrochemical energy storage devices due to their high power and long cycle life characteristics with fast response time.As one of the essential components of LICs,the electrolytes not only provide the anions and cations required during charge and discharge processes,but also supply the liquid environment for ions to migrate between anodes and cathodes in LIC cells.It is well accepted that propylene carbonate(PC) cannot be used as a single solvent for Li-ion electrolyte due to the failure to form stable SEI film on graphite surface.In this work,the compatibility of PC-based electrolyte with commercial soft carbon anode and activated carbon cathode has been validated by using the laminated pouch LIC cells.The effects of additives on the electrochemical properties of PC-based LICs have been systematically investigated.Ethylene sulfite(ES) was proved to be an effective additive to promote capacity retention at high C-rate,which is superior to vinylene carbonate and fluoroethylene carbonate.The addition of 5 wt% ES plays an important role in reducing internal resistance,as well as improving electrochemical stability and low-temperature performances.This study is expected to be beneficial to explore robust electrolyte/additive combinations for LICs to reduce the internal resistance and to improve the lowtemperature performances.展开更多
Development of active and non-noble metal-based catalyst for H2 production via NH3 decomposition is crucial for the implementation of NH3 as a H2 carrier.Co-based catalysts have received increasing attention because o...Development of active and non-noble metal-based catalyst for H2 production via NH3 decomposition is crucial for the implementation of NH3 as a H2 carrier.Co-based catalysts have received increasing attention because of its high intrinsic activity and moderate cost.In this work,we examined the effect of BaNH,CaNH and Mg3 N2 on the catalytic activity of Co in the NH3 decomposition reaction.The H2 formation rate ranks the order as Co-BaNH>Co-CaNH>Co-Mg3 N2≈Co/CNTs within a reaction temperature range of 300-550℃.It is worth pointing out that the H2 formation rate of Co-BaNH at 500℃reaches20 mmolH2 gcat-1 min-1,which is comparable to those of the active Ru/Al2 O3(ca.17 mmolH2 gcat-1 min1)and Ru/AC(21 mmolH2 gcat-1 min-1)catalysts under the similar reaction conditions.In-depth research shows that Co-BaNH exhibits an obviously higher intrinsic activity and much lower Ea(46.2 kJ mol-1)than other Co-based catalysts,suggesting that BaNH may play a different role from CaNH,Mg3 N2 and CNTs during the catalytic process.Combined results of XRD,Ar-TPD and XAS show that a[Co-N-Ba]-like intermediate species is likely formed at the interface of Co metal and BaNH,which may lead to a more energy-efficient reaction pathway than that of neat Co metal for NH3 decomposition.展开更多
Composite polymer electrolytes based on mixing soft-segment waterborne polyurethane （WPU） and 1-butyl-3-methylimidazolium bis[（trifluoromethyl）sulfonyl]imide （BMImTFSI） have been prepared and characterized. The ...Composite polymer electrolytes based on mixing soft-segment waterborne polyurethane （WPU） and 1-butyl-3-methylimidazolium bis[（trifluoromethyl）sulfonyl]imide （BMImTFSI） have been prepared and characterized. The addition of BMImTFSI results in an increase of the ionic conductivity. At high BMImTFSI concentration （BMImTFSI/WPU = 3 in weight ratio）, the ionic conductivity reaches 4.27 × 10^-3 S/cm at 30 ℃. These composite polymer electrolytes exhibit good thermal and electrochemical stability, which are high enough to be applied in lithium batteries.展开更多
A series of novel aromatic poly ( amide imide)s containing phthalazinone moieties were prepared from 2-(4-aminophenyl)-4-[3-methyl-4-(4-aminophenoxy)-2,3-phthalazinone-1], a novel diamine 1 with four diimide-dicarboxy...A series of novel aromatic poly ( amide imide)s containing phthalazinone moieties were prepared from 2-(4-aminophenyl)-4-[3-methyl-4-(4-aminophenoxy)-2,3-phthalazinone-1], a novel diamine 1 with four diimide-dicarboxylic acids by Yamazaki phosphorylation method with the inherent viscosity of 0.36~0.65 dL/g. These polymers had high glass transition temperatures above 300C and they lost 10% weight between 426~475C in N2. The structure of diamine 1 and the polymers was confirmed by IR, 1H NMR and MS. The obtained polymers were readily soluble in polar solvents such as NMP, m-cresol etc. and easily cast into tough, flexible films. The X-ray indicated that they are all amorphous.展开更多
Three novel poly(ether imide)s were synthesized by one-step solution polymerization from 2-(3, 4-dicarboxyl-N-phenyl)-4-(3, 4-dicarboxyl-phenoxyl-4-(2-methyl)-phenyl)-2, 3- phthal-azin-1-one dianhydride and three amin...Three novel poly(ether imide)s were synthesized by one-step solution polymerization from 2-(3, 4-dicarboxyl-N-phenyl)-4-(3, 4-dicarboxyl-phenoxyl-4-(2-methyl)-phenyl)-2, 3- phthal-azin-1-one dianhydride and three amines, and characterized. The polymers show good solubility and thermal properties.展开更多
With the goal of improving processability of imide oligomers and achieving high toughness of thermosetting polyimides, a series of 4-phenylethynylphthalic anhydride（PEPA）-terminated imide oligomers prepared by the r...With the goal of improving processability of imide oligomers and achieving high toughness of thermosetting polyimides, a series of 4-phenylethynylphthalic anhydride（PEPA）-terminated imide oligomers prepared by the reaction of 2,3,3＇,4＇-diphenyl ether tetracarboxylic acid dianhydride（a-ODPA） and 3,4＇-oxydianiline（3,4＇-ODA） with different molecular weights（degree of polymerization： n = 1？9） were formed. The resultant oligomers with different molecular weights were characterized for their chemical architecture, cure behavior, thermal properties, solubility in organic solvents and rheological characteristics. Besides, the thermal properties and tensile test of cured polyimide films were also evaluated. The imide oligomer（degree of polymerization： n = 1） has some somewhat crystalline phase, and imide oligomers（degree of polymerization： n = 2？9） showed excellent solubility（40 wt%） in N-methyl-2-pyrrolidone（NMP） and N,Ndimethylacetamide（DMAc） at room temperature. Furthermore, the rheological properties of imide oligomers showed very low melt viscosity and wider processing window. The cured films exhibited good thermal properties with the glass transition temperatures of 282？373 ？C and 5 wt% thermal decomposition temperatures higher than 551 ？C in nitrogen atmosphere. The elongation at break of the prepared films was found to be high（almost 〉 9.3%）.展开更多
The earth-abundant magnesium metal is a kind of promising anode material due to its low reduction potential (-2.356V vs. SHE), high volumetric and gravimetric specific capacities of 3882 mAh cm-3 and 2234 mAh g_1 resp...The earth-abundant magnesium metal is a kind of promising anode material due to its low reduction potential (-2.356V vs. SHE), high volumetric and gravimetric specific capacities of 3882 mAh cm-3 and 2234 mAh g_1 respectively [1]. Moreover, the magnesium anode shows high safety due to the non-dentritic electrodeposition mechanism during cycling, which is related to the strong Mg-Mg bonding and the consequent high energy barrier between the crystal boundaries of different crystal orientation [2].展开更多
基金financially supported by the National Key Research and Development Program of China(No.2022YFB3603105)Key Programs of the Chinese Academy of Sciences(No.ZDRW-CN-2023-3-2)+1 种基金the National Natural Science Foundation of China(No.51803221)Natural Science Foundation of Beijing Municipality(No.2202068)。
文摘The traditional high-temperature preparation process of polyimide can cause many problems and limits the wider application in extreme conditions.An important challenge to be solved urgently is the reduction of imidization temperature.In this work,twelve kinds of polyimide films with different chain rigidity were prepared at low temperature of 200℃,in the absence or presence of imidazole used as the catalyst.The molecular rigidity and free volume were theoretically calculated,and relationship between structure and properties were systematically studied.The results show that imidization reaction under low temperatures is significantly affected by the rigidity of molecula r chains.The rigid structure of polyimide is not conducive to the low-temperature imidization,but this adverse effect can be eliminated by adding catalyst,resulting the notably increased imidization degree.The optical and thermal properties can be improved to a certain extent for the chemically catalyzed system,resulting in relatively higher heat resistance and thermal stability.While the mechanical performance could be determined by com plicating factors,greatly different from polyimide films prepa red by high temperature method.To investigate aggregation structures of film s,the effect of chain rigidity and catalyst on the stacking or orientation of molecular chains was further elaborated.This wo rk can contribute to the understanding of chemically catalyzed imidization that is rarely reported in the existing research,and will provide guidance for the low-temperature preparation of high-performance polyimides.
基金financially supported by the National Basic Research Program of China(No.2014CB643603)the National Natural Science Foundation of China(No.51173178)
文摘In this study, polyimide fibers at different stages of imidization were characterized by TGA, DSC, and FTIR. The imidization degree （ID） calculated by TGA was based on the weight loss of each sample, which was caused by the imidization of residual amic acid groups. The results of TGA showed good regularity with the thermal treatment temperature of the PI fibers. For DSC, the ID was calculated based on the area of endothermal peak of each sample. Compared with TGA, DSC showed a relatively higher value because the endothermal peak was reduced by the exothermic re-formation of polyamic acid which may be partially degraded during thermal treatment. The IDs obtained by the FTIR spectra generally showed poorer regularities than those obtained by both TGA and DSC, especially for the results calculated using the 730 cm^-1 band. Based on the 1350 cm^-1 band, the obtained IDs showed better agreement with the TGA or DSC results. The results obtained by these three methods were compared and analyzed. The ID obtained by TGA showed much more reliability among these three methods.
文摘In order to lower the imidization temperature of polyamic acids（PAA）, the catalytic activities of the curing agents p-hydroxybenzoic acid（PHA）, quinoline（QL）, benzimidazole（BI）, benzotriazole（BTA）, triethylamine（Et_3N） and 1, 8-diazabicyclo [5.4.0]undec-7-ene（DBU） were investigated in the process of thermal imidization of PAA. In addition, the effect of these various curing agents on the thermal stabilities and mechanical properties of the resultant polyimide（PI） films was determined. Quinoline was found to be an effective curing accelerator in the use of two-step method for synthesizing PI. Due to its moderate base strength, low steric crowding effect and moderate boiling point, quinoline could not only accelerate PAA to achieve imidization completely at 180 ℃, but also maintain the mechanical properties and thermal stability of the ordinary PI film. Any residual quinoline could be removed from PI films by heating at 250 ℃ for 4 h.
文摘2-substituted-1-amino-o-carboranes 2-R-1-NH_(2)-o-C_(2)B_(10)H_(10)(R=CH_(3),1a;R=Ph,1b)were synthesized and the reactions of these compounds with the yttrium dialkyl complex[Y(L)(CH_(2)SiMe3)_(2)](L=[2-(2,5-Me_(2)C_(4)H_(2)N)C_(6)H4NC(Ph)=NDipp]-,Dipp=2,6-iPr_(2)C_(6)H_(3))were investigated.The 1H NMR spectroscopy indicate that the reaction of ytrrium dialkyl complex with one equivalent of 2-R-1-NH_(2)-o-C_(2)B_(10)H_(10) produce the mixture of ytrrium alkyl-amido complex[Y(L)(2-R-1-NH-o-C_(2)B_(10)H_(10))(CH_(2)SiMe3)](R=CH_(3),2a;R=Ph,2b)and bis(amido)complex[Y(L)(2-R-1-NH-o-C_(2)B_(10)H_(10))_(2)](R=CH_(3),3a;R=Ph,3b).The yttrium bridging imido complex[Y(L)(2-CH_(3)-1-N-o-C_(2)B_(10)H_(10))]_(2)(4a)was obtained by heating the mixture at 55℃for 12 h.Complex 3a was isolated and characterized by treating the yttrium dialkyl complex with two equivalents of 1a.The structures of complexes 3a and 4a were verified by single-crystal Xray diffraction.CCDC:2424136,3a;2424137,4a.
基金the National Natural Science Foundation of China(No.21672147)Shanghai University of Traditional Chinese Medicine for financial support。
文摘Glycosyl imidates are among the pioneering donors for catalytic glycosylation.We report a new generation of imidates featuring the presence of a pentafluorophenyl group,introduced via substitution on imidoyl fluoride which is easily prepared,stable and user-friendly.The resulting donors exhibit exceptional shelf stability while can be readily activated to achieve high-yielding glycosylation,encompassing comprehensively aldosyl,ketosyl and ulosonyl donors,and both O-and N-glycosylation acceptors.Notably,the reactivity gradient across different generations of imidates,coupled with the accessible imidate acceptor from selective reaction of imidoyl fluoride at the anomeric hydroxyl group,enables a fully catalytic one-pot synthesis of oligosaccharides.
文摘The major challenge in photocatalytic water splitting lies in water oxidation reactions,which still suffer from poor charge separation.This study overcame inefficient charge separation by establishing a robust interfacial electric field through the electrostatic-driven assembly of Co_(3)O_(4) nanoparticles with a perylene imide supramolecule(PDINH).The well-aligned band structures and intimate interfacial contact in the PDINH/Co_(3)O_(4) heterostructure create an enhanced interfacial electric field that is 4.1-and 53.2-fold stronger than those of individual PDINH and Co_(3)O_(4),thus promoting directional charge separation and transfer.Moreover,S-scheme charge transfer strongly preserves the oxidative holes in PDINH to drive efficient water oxidation reactions.Consequently,PDINH/Co_(3)O_(4) composite achieves a photocatalytic oxygen evolution rate of 29.26 mmol g^(–1) h^(–1) under visible light irradiation,8.2-fold improvement over pristine PDINH,with an apparent quantum yield of 6.66%at 420 nm.This study provides fundamental insights into interfacial electric field control for the development of high-performance organic photocatalysts for efficient water oxidation.
基金supported by the National Natural Science Foundation of China(No.52273264)。
文摘Polymeric carbon nitride(PCN)has garnered increasing attention as a metal-free photocatalyst with a suitable band gap.In efforts to enhance its photocatalytic performance,researchers have examined various PCN materials,including poly(heptazine imide)(PHI)and poly(triazine imide)(PTI),two isomers within the PCN family that exhibit distinct and superior photocatalytic activity compared to other forms.The challenge,however,lies in the common practice among researchers to categorize PHI and PTI along with other PCN types under the overarching term“g-C_(3)N_(4),”which significantly impedes optimization efforts.The objective of this review is to provide comprehensive insights into the structural features,photoelectrochemical properties,and effective characterization methods employed for distinguishing between PHI and PTI materials.The review also summarizes various optimization strategies,such as crystallinity adjustments,defect engineering,morphology control,constructing heterojunction,and atomic-level metal loading dispersion,to elevate the photocatalytic activity of PHI and PTI,in addition to summarizing the history of carbon nitride development.Furthermore,this review highlights the primary applications of PHI and PTI,encompassing nitrogen fixation,biomass conversion,organic synthesis,CO_(2)reduction,pollutant degradation,H_(2)O_(2)production,and photocatalytic water splitting.Lastly,the prospects and challenges associated with further advancing PHI and PTI are thoroughly examined.
基金supported by the National Natural Science Foundation of China(Nos.22008185 and 22008188)the Shaanxi Provincial Key Research and Development Program(No.2022GY-166)+1 种基金the Scientific Research Program Funded by Shaanxi Provincial Education Department(No.22JK0406)the Scientific Research Program Funded by Shaanxi Provincial Education Department(No.23JC033).
文摘Poly(triazine imide),as a kind of highly crystalline g-C_(3)N_(4),exhibits a promising potential for photo-catalytic hydrogen production,however,some drawbacks still limit its photocatalytic performance.The strategy of constructing S-scheme heterojunction with different semiconductor photocatalysts enables the effective separation of photogenerated electrons and holes,and the strong oxidative and reductive properties of the original photocatalysts could be retained,which will significantly improve the photo-catalytic activity.In this work,we synthesized the organic-organic S-scheme heterojunction between PTI and organic small molecule poly(barbituric acid)(PBA)by hydrogen bond self-assembly method,which results in a significant enhancement of photocatalytic H_(2)production activity.The H_(2)production rate of the optimum PBA/PTI-2 sample under visible light irradiation is about 0.92 mmol g^(-1),which is 5.5 times higher than that of PTI and 14.4 times higher than that of PBA.This excellent photocatalytic performance is attributed to the successful construction of S-scheme heterojunction between PTI and PBA,which ef-fectively accelerates carrier transport and spatial segregation by the formation of a built-in electric field and band bending at the interface.In addition,the S-scheme heterojunction could also reserve the maxi-mum redox capability and enhance the light absorption of the prepared photocatalytic system.This work provides a new strategy and understanding for the design and development of organic-organic S-scheme heterojunction photocatalysts.
基金financial support from the National Natural Science Foundation of China(Grant No.21801016)the Science and Technology on Applied Physical Chemistry Laboratory(Grant No.6142602220304)。
文摘In order to achieve a wider range of ionizing radiations detection,novel fluorescence sensing materials have been developed that utilize the fluorescence enhancement phenomenon caused by the intramolecular photoinduced electron transfer(PET)effect.Two perylene diimide isomers PDI-P and PDI-B were designed and synthesized,and their molecular structures were characterized by high-resolution Fourier transform mass spectrometry(HRMS),nuclear magnetic resonance hydrogen and carbon spectroscopy(~1H and~(13)C NMR).The interaction between ionizing radiation and fluorescent molecules was simulated by HCl titration.The results show that combining PDIs and HCl can improve fluorescence through the retro-PET process.Despite the similarities in chemical structures,the fluorescent enhancement multiple of PDI-B with aromatic amine as electron donor is much higher than that of PDI-P with alkyl amine.In the direct irradiation experiments of ionizing radiation,the emission enhancement multiples of PDI-P and PDI-B are 2.01 and 45.4,respectively.Furthermore,density functional theory(DFT)and time-dependent density functional theory(TDDFT)calculations indicate that the HOMO and HOMO-1 energy ranges of PDI-P and PDI-B are 0.54 e V and 1.13 e V,respectively.A wider energy range has a stronger driving force on electrons,which is conducive to fluorescence quenching.Both femtosecond transient absorption spectroscopy(fs-TAS)and transient fluorescence spectroscopy(TFS)tests show that PDI-B has shorter charge separation lifetime and higher electron transfer rate constant.Although both isomers can significantly reduce LOD during PET process,PDI-B with aromatic amine has a wider detection range of 0.118—240 Gy due to its larger emission enhancement,which is a leap of three orders of magnitude.It breaks through the detection range of gamma radiation reported in existing studies,and provides theoretical support for the further study of sensitive and effective new materials for ionizing radiation detection.
基金supported by the National Natural Science Foundation of China (52373065)the Joint Fund of Ministry of Education for Equipment Pre-research (8091B032206)+1 种基金the Guang Dong Basic and Applied Basic Research Foundation (2021A1515111067,2023A1515010735)the start-up funding of“Hundred Talent Program”from Sun Yat-sen University。
文摘The notorious growth of zinc dendrite and the water-induced corrosion of zinc metal anodes(ZMAs)restrict the practical development of aqueous zinc ion batteries(AZIBs).In this work,a zinc metallized,imide-pillared covalent organic framework(ZPC)protective film has been engineered as a stable Zn^(2+)ion-conducting interphase to modulate interfacial kinetics and suppress side reactions for ZMAs.Compared to bare Zn,ZPC@Zn exhibits a higher Zn^(2+)ionic conductivity,a larger Zn^(2+)transference number,a lower electronic conductivity,a smaller desolvation activation energy and correspondingly a significant suppression of corrosion,hydrogen evolution and Zn dendrites.Impressively,the ZPC@Zn||ZPC@Zn symmetric cell obtains a cycling lifespan over 3000 h under 5 mA cm^(-2)for 1 mA h cm^(-2).The ZPC@Zn||NH_(4)V_(4)O_(10)coin-type full battery delivers a specific capacity of 195.8 mA h g^(-1)with a retention rate of78.5%at 2 A g^(-1)after 1100 cycles,and the ZPC@Zn||NH_(4)V_(4)O_(10) pouch full cell shows a retention of70.1%in reversible capacity at 3 A g^(-1)after 1100 cycles.The present incorporation of imide-linked covalent organic frameworks in the surface modification of ZMAs will offer fresh perspectives in the search for ideal protective films for the practicality of AZIBs.
基金financially supported by the National Natural Science Foundation of China(No.52303010)Key-Area Research and Development Program of Guangdong province(No.2019B010941001)+2 种基金Key Technology of Liquid Crystal Polymer Material for 5G/6G High Frequency Communication(No.JSGGZD20220822095201003)Songshan Lake Materials Laboratory(No.2021SLABFK01)the Guangdong Basic and Applied Basic Research Foundation(No.2021A1515110143)。
文摘The evolution of high-frequency communication has accentuated the significance of controlling dielectric properties in polymer media.Traditionally,it has been theorized that rigid molecular chains lead to lower dielectric loss.However,the validity of this proposition at high frequencies remains uncertain.To scrutinize the correlation between chain flexibility and dielectric properties,we synthesized six poly(ester imide)s(PEIs)with systematically varied molecular chain flexibilities by modifying the ester's substitution on the aromatic ring.The introduction of ester bonds bestowed all PEI films with a low dielectric dissipation factor(D_(f)),ranging from 0.0021 to 0.0038 at 10 GHz in dry conditions.The dry D_(f)displayed a pattern consistent with volume polarizability(P/V).Unexpectedly,PI-mmm-T,featu ring the most flexible molecular chain,exhibited the lowest dielectric loss under both dry(0.0021@10 GHz)and hygroscopic(0.0029@10 GHz)conditions.Furthermore,the observed increase in D_(f)after humidity absorption suggests that the high dielectric loss of PEI in applications may be attributed to its hygroscopic nature.Molecular simulations and characterization of the aggregation structure revealed that the smaller cavities within flexible molecular chains,after close stacking,impede the entry of water molecules.Despite sacrificing high-temperature resistance,the precursor exhibited enhanced solubility properties and could be processed into high-quality films.Our research unveils new insights into the relationship between flexibility and highfrequency dielectric loss,offering innovative perspectives on synthesizing aromatic polymers with exceptional dielectric properties.
基金financially supported by National Basic Research Program of China(No.2014CB643604)
文摘The thermal and mechanical properties of the chemically imidized polyimide(CIPI) films and thermally imidized polyimide(TIPI) films were investigated systematically. Experimental results indicated that the CIPI films show dramatically enhanced tensile strength and modulus with obviously reduced coefficient of thermal expansion(CTE) in comparison with TIPI films. These enhancements results from the high in-plane orientation and close packing of the CIPI backbones. Compared with thermal imidization which starts at about 140 °C, the chemical imidization activated by acetic anhydride and isoquinoline initiates the cyclization even at room temperature.The resulting imide rings restrict the mobility of polymer chains and lead to the in-plane orientation with solvent evaporation.Additionally, fewer small molecules remain in the films after treated at 120 °C by chemical imidization than by thermal imidization. The polymer chain plasticization caused by the evaporation of small molecules at high temperature is obviously restricted. Moreover, the partially imidized polymer inhibits the decomposition of mainchains that occurs at subsequent high temperature process, being beneficial to the formation of high molecular weight PI films. Hence, chemical imidization pathway shows apparent advantage to produce PI films with great combined properties, including high modulus, strength and toughness, as well as high thermal dimension stability etc.
文摘N-Methyl-N-propylpiperidiniumbis（trifluoromethanesulfonyl）imide （PP13TFSI）, bis（triflu- oromethanesulfonyl）imide lithium salt （LiTFSI）, and poly（vinylidene difluoride-co- hexafluoropropylene） （P（VdF-HFP）） were mixed and made into ionic liquid gel polymer electrolytes （ILGPEs） by solution casting. The morphology of ILGPEs was observed by scanning electron microscopy. It was found that the ILGPE had a loosened structure with liquid phase uniformly distributed. The ionic conductivity, lithium ion transference num- bet and electrochemical window were measured by electrochemical impedance spectroscopy, chronoamperometric and linear sweep voltammetry. The ionic conductivity and lithium ion transference number of this ILGPE reached 0.79 mS/cm and 0.71 at room temperature, and the electrochemical window was 0 to 5.1 V vs. Li＋/Li. Battery tests indicated that the ILGPE is stable when being operated in Li/LiFePO4 batteries. The discharge capacity maintained at about 135, 117, and 100 mAh/g at 30, 75, and 150 mA/g rates, respectively. The capacity retentions were almost 100% after 100 cycles without little capacity fading.
基金the National Natural Science Foundation of China(Nos.52077207,51822706,51777200 and 51772127)Beijing Natural Science Foundation(No.JQ19012)Dalian National Laboratory for Clean Energy Cooperation Fund,the CAS(No.DNL201912)。
文摘Nowadays,lithium-ion capacitors(LICs) have become a type of important electrochemical energy storage devices due to their high power and long cycle life characteristics with fast response time.As one of the essential components of LICs,the electrolytes not only provide the anions and cations required during charge and discharge processes,but also supply the liquid environment for ions to migrate between anodes and cathodes in LIC cells.It is well accepted that propylene carbonate(PC) cannot be used as a single solvent for Li-ion electrolyte due to the failure to form stable SEI film on graphite surface.In this work,the compatibility of PC-based electrolyte with commercial soft carbon anode and activated carbon cathode has been validated by using the laminated pouch LIC cells.The effects of additives on the electrochemical properties of PC-based LICs have been systematically investigated.Ethylene sulfite(ES) was proved to be an effective additive to promote capacity retention at high C-rate,which is superior to vinylene carbonate and fluoroethylene carbonate.The addition of 5 wt% ES plays an important role in reducing internal resistance,as well as improving electrochemical stability and low-temperature performances.This study is expected to be beneficial to explore robust electrolyte/additive combinations for LICs to reduce the internal resistance and to improve the lowtemperature performances.
基金financial supports from the Project of the National Natural Science Foundation of China(Grant Nos.21633011and 21872137)“Transformational Technologies for Clean Energy and Demonstration”+2 种基金Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA21000000)Youth Innovation Promotion Association CAS(No.2018213)the Shanghai Synchrotron Radiation Facility(SSRF)for providing the beam time。
文摘Development of active and non-noble metal-based catalyst for H2 production via NH3 decomposition is crucial for the implementation of NH3 as a H2 carrier.Co-based catalysts have received increasing attention because of its high intrinsic activity and moderate cost.In this work,we examined the effect of BaNH,CaNH and Mg3 N2 on the catalytic activity of Co in the NH3 decomposition reaction.The H2 formation rate ranks the order as Co-BaNH>Co-CaNH>Co-Mg3 N2≈Co/CNTs within a reaction temperature range of 300-550℃.It is worth pointing out that the H2 formation rate of Co-BaNH at 500℃reaches20 mmolH2 gcat-1 min-1,which is comparable to those of the active Ru/Al2 O3(ca.17 mmolH2 gcat-1 min1)and Ru/AC(21 mmolH2 gcat-1 min-1)catalysts under the similar reaction conditions.In-depth research shows that Co-BaNH exhibits an obviously higher intrinsic activity and much lower Ea(46.2 kJ mol-1)than other Co-based catalysts,suggesting that BaNH may play a different role from CaNH,Mg3 N2 and CNTs during the catalytic process.Combined results of XRD,Ar-TPD and XAS show that a[Co-N-Ba]-like intermediate species is likely formed at the interface of Co metal and BaNH,which may lead to a more energy-efficient reaction pathway than that of neat Co metal for NH3 decomposition.
基金financially supported by the National 863 Program(No.2007AA03Z226)the National Key Program for Basic Research of China(No.2002CB211800 and 2009CB220100).
文摘Composite polymer electrolytes based on mixing soft-segment waterborne polyurethane （WPU） and 1-butyl-3-methylimidazolium bis[（trifluoromethyl）sulfonyl]imide （BMImTFSI） have been prepared and characterized. The addition of BMImTFSI results in an increase of the ionic conductivity. At high BMImTFSI concentration （BMImTFSI/WPU = 3 in weight ratio）, the ionic conductivity reaches 4.27 × 10^-3 S/cm at 30 ℃. These composite polymer electrolytes exhibit good thermal and electrochemical stability, which are high enough to be applied in lithium batteries.
文摘A series of novel aromatic poly ( amide imide)s containing phthalazinone moieties were prepared from 2-(4-aminophenyl)-4-[3-methyl-4-(4-aminophenoxy)-2,3-phthalazinone-1], a novel diamine 1 with four diimide-dicarboxylic acids by Yamazaki phosphorylation method with the inherent viscosity of 0.36~0.65 dL/g. These polymers had high glass transition temperatures above 300C and they lost 10% weight between 426~475C in N2. The structure of diamine 1 and the polymers was confirmed by IR, 1H NMR and MS. The obtained polymers were readily soluble in polar solvents such as NMP, m-cresol etc. and easily cast into tough, flexible films. The X-ray indicated that they are all amorphous.
基金This work was sponsored by the National Natural Science Foundation of China (No. 59473901).
文摘Three novel poly(ether imide)s were synthesized by one-step solution polymerization from 2-(3, 4-dicarboxyl-N-phenyl)-4-(3, 4-dicarboxyl-phenoxyl-4-(2-methyl)-phenyl)-2, 3- phthal-azin-1-one dianhydride and three amines, and characterized. The polymers show good solubility and thermal properties.
基金financially supported by the National 863 Project of China(No.2012AA03A212)the National Natural Science Foundation of China(No.51203019)
文摘With the goal of improving processability of imide oligomers and achieving high toughness of thermosetting polyimides, a series of 4-phenylethynylphthalic anhydride（PEPA）-terminated imide oligomers prepared by the reaction of 2,3,3＇,4＇-diphenyl ether tetracarboxylic acid dianhydride（a-ODPA） and 3,4＇-oxydianiline（3,4＇-ODA） with different molecular weights（degree of polymerization： n = 1？9） were formed. The resultant oligomers with different molecular weights were characterized for their chemical architecture, cure behavior, thermal properties, solubility in organic solvents and rheological characteristics. Besides, the thermal properties and tensile test of cured polyimide films were also evaluated. The imide oligomer（degree of polymerization： n = 1） has some somewhat crystalline phase, and imide oligomers（degree of polymerization： n = 2？9） showed excellent solubility（40 wt%） in N-methyl-2-pyrrolidone（NMP） and N,Ndimethylacetamide（DMAc） at room temperature. Furthermore, the rheological properties of imide oligomers showed very low melt viscosity and wider processing window. The cured films exhibited good thermal properties with the glass transition temperatures of 282？373 ？C and 5 wt% thermal decomposition temperatures higher than 551 ？C in nitrogen atmosphere. The elongation at break of the prepared films was found to be high（almost 〉 9.3%）.
基金supported by the National Natural Science Foundation of China (no. 51772068, 21773049)
文摘The earth-abundant magnesium metal is a kind of promising anode material due to its low reduction potential (-2.356V vs. SHE), high volumetric and gravimetric specific capacities of 3882 mAh cm-3 and 2234 mAh g_1 respectively [1]. Moreover, the magnesium anode shows high safety due to the non-dentritic electrodeposition mechanism during cycling, which is related to the strong Mg-Mg bonding and the consequent high energy barrier between the crystal boundaries of different crystal orientation [2].
