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Light-induced stepped thermal relaxation in a Hofmann-type metal-organic framework

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Science China chemistry 2024年第6期67卷 1983-1989页

作者： Wen Cui Wei-Wei Wu Ze-Yu Ruan Yan-Cong Chen Guang-Jun Zeng Guan-Xi Chen Si-Guo Wu Zhao-Ping Ni Ming-Liang Tong Key Laboratory of Bioinorganic and Synthetic chemistry of Ministry of Education School of ChemistryInstitute of Green Chemistry and Molecular EngineeringGuangdong Basic Research Center of Excellence for Functional Molecular EngineeringSun Yat-sen UniversityGuangzhou510275China

Spin-crossover(SCO)materials with light-induced multistability have potential applications in multi-addressable opto-magnetic memory devices and multiple switches.Here,we reported a three-dimensional Hofmann-type metal-organic framework(MOF)[Fe(bpy){Pt(CN)_(4)}]·coumarin(1·coumarin,bpy=4,4′-bipyridine),which exhibits an incomplete and hysteretic SCO behavior.Most importantly,the light-induced stepped thermal relaxation(LISTR)with obvious magnetic plateau for a hidden intermediate spin state is firstly realized.This hidden spin state is also observed for the first time in the thermal relaxation after light-assisted spin state annealing(LASSA).Meanwhile,an extremely rare bi-directional light-induced excited spin-state trapping(LIESST)with the highest reverse-LIESST temperature is observed.Therefore,five spin states can be captured in 1·coumarin and the tristability can be modulated below 102 K through the excitation-relaxation mechanism.Hence,the light-and temperatureinduced multistability provides a new strategy for developing multistable materials.

关键词： light magnetic multistability iron metal-organic framework spin-crossover

Covalent triazine frameworks modified by ultrafine Pt nanoparticles for efficient photocatalytic hydrogen production

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Nano Research 2024年第6期17卷 4908-4915页

作者： Xu Han Xueying Ge Wen-Wen He Wangwang Shen Tao Zhou Jian-Sen Wang Rong-Lin Zhong Abdullah MAl-Enizi Ayman Nafady Shengqian Ma School of chemistry and Life Science Advanced Institute of Materials ScienceChangchun University of TechnologyChangchun 130012China Laboratory of Theoretical and Computational chemistry Institute of Theoretical ChemistryCollege of ChemistryJilin UniversityChangchun 130021China Department of chemistry University of North Texas1508 W.Mulberry St.DentonTX 76201USA Department of chemistry College of ScienceKing Saud UniversityRiyadh 11451Saudi Arabia

Pt nanoparticles(PtNPs)as active species have always been considered as one of the best semiconductor materials for photocatalytic hydrogen production.In this study,a Schottky heterojunction has been successfully constructed by evenly loading ultrafine PtNPs onto a triazine-based covalent organic frameworks(COFs).This strategy maintained the high activity of these ultra-small PtNPs while maximizing the utilization of the Pt active sites.The fabricated PtNPs@covalent triazine-based framework-1(CTF-1)composite accomplished a significantly high rate of hydrogen evolution(20.0 mmol·g^(−1)·h^(−1),apparent quantum efficiency(AQE)=7.6%,atλ=450 nm)with 0.40 wt.%Pt loading,giving rise to a 44-fold-increase in the efficiency of the photocatalytic hydrogen production compared to the pristine CTF-1.Theoretical calculations revealed that the strong electron transfer(Q(Pt)=−0.726 qe,in the analysis of Bader charge,Q(Pt)is the charge quantity transferred from Pt cluster to CTF-1,and qe is the unit of charge transfer quantity)between PtNPs and CTF-1 triggers a strong interaction,which makes PtNPs being firmly attached to the structure of CTF-1,thereby enabling high stability and excellent hydrogen production efficiency.Importantly,the hydrogen binding free energy(ΔGH*)of PtNPs@CTF-1 is much lower than that of the unmodified CTF-1,leading to a much lower intermediate state and hence a significant improvement in photocatalytic performance.The overall findings of this work provide a new platform to incorporate metallic NPs into COFs for the design and fabrication of highly efficient photocatalysts.

关键词： Pt nanoparticles covalent triazine-based framework-1(CTF-1) photocatalysts hydrogen evolution reaction

Engineering molecular regulation for SiO_(x) with long-term stable cycle and high Coulombic efficiency as lithium-ion battery anodes

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Rare Metals 2024年第2期43卷 588-598页

作者： Fei Wang Han Gao Zhao-Yu Niu Yao-Peng Zheng Ming-Yan Chuai Jia-Nan Xu State Key Laboratory of Electroanalytical chemistry Changchun Institute of Applied ChemistryChinese Academy of SciencesChangchun130022China University of Science and Technology of China Hefei230026China

In the current situation where the practical application of silicon anode materials encounters great challenges,silicon oxide(SiO_(x),0≤x≤2)has attracted the attention of researchers due to its relatively small volume expansion,stable cycling performance,and low cost,which is possible to realize commercial applications earlier than silicon anode.However,it remains a challenge to prepare SiO_(x)materials with long-term stable cycling performance and high Coulombic efficiency using low-cost methods.In this work,SiO_(x)anode material with high Coulombic efficiency and good long-term cycling stability was prepared at a low cost by hydrolysis of siloxane and in situ polymerization of phenolic resin.The hydrolysis of siloxane was further regulated by different silane coupling agents to regulate the size and microstructure of prepared SiO_(x)materials,which displayed the substantially improved electrochemical performance.The excellent electrochemical performance of SiO_(x)prepared by regulated hydrolysis of siloxane with silane coupling agents is attributed to the effect of silane coupling agent on size and microstructure of SiO_(x),revealing that the strategy of modulating the hydrolysis of siloxane by silane coupling agent is a potential method to prepare high-performance SiO_(x)materials.

关键词： Hydrolysis Silane coupling agent Long cycle SiO_(x) anode Lithium-ion battery(LIB)

Solid-state impedance spectroscopy studies of dielectric properties and relaxation processes in Na_(2)O–V_(2)O_(5)–Nb_(2)O_(5)–P_(2)O_(5) glass

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International Journal of Minerals,Metallurgy and Materials 2024年第1期31卷 186-196页

作者： Sara Marijan Luka Pavic Division of Materials chemistry Ruđer Boskovic InstituteBijenicka 54HR-10000 ZagrebCroatia

Solid-state impedance spectroscopy(SS-IS)was used to investigate the influence of structural modifications resulting from the addition of Nb2O5 on the dielectric properties and relaxation processes in the quaternary mixed glass former(MGF)system 35Na_(2)O–10V_(2)O_(5)–(55-x)P_(2)O_(5)–xNb_(2)O_(5)(x=0–40,mol%).The dielectric parameters,including the dielectric strength and dielectric loss,are determined from the frequency and temperature-dependent complex permittivity data,revealing a significant dependence on the Nb2O5 content.The transition from a predominantly phosphate glass network(x<10,region I)to a mixed niobate–phosphate glass net-work(10≤x≤20,region II)leads to an increase in the dielectric parameters,which correlates with the observed trend in the direct-cur-rent(DC)conductivity.In the predominantly niobate network(x≥25,region III),the highly polarizable nature of Nb5+ions leads to a fur-ther increase in the dielectric permittivity and dielectric strength.This is particularly evident in Nb-40 glass-ceramic,which contains Na_(13)Nb_(35)O_(94) crystalline phase with a tungsten bronze structure and exhibits the highest dielectric permittivity of 61.81 and the lowest loss factor of 0.032 at 303 K and 10 kHz.The relaxation studies,analyzed through modulus formalism and complex impedance data,show that DC conductivity and relaxation processes are governed by the same mechanism,attributed to ionic conductivity.In contrast to glasses with a single peak in frequency dependence of imaginary part of electrical modulus,M″(ω),Nb-40 glass-ceramic exhibits two distinct contributions with similar relaxation times.The high-frequency peak indicates bulk ionic conductivity,while the additional low-fre-quency peak is associated with the grain boundary effect,confirmed by the electrical equivalent circuit(EEC)modelling.The scaling characteristics of permittivity and conductivity spectra,along with the electrical modulus,validate time-temperature superposition and demonstrate a strong correlation with composition and modific

关键词： phosphate glasses glass-ceramics impedance spectroscopy dielectric properties relaxation processes permittivity scaling conductivity scaling modulus formalism

Dielectric Constant Calculation of Poly(vinylidene fluoride)Based on Finite Field and Density Functional Theory

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Chinese Journal of Polymer Science 2024年第5期42卷 655-662,I0009页

作者： Yong-Zhi Lin Lu-Kun Feng Ya-Dong Li Chao-Fan Chang Cai-Zhen Zhu Ming-Liang Wang Jian Xu College of chemistry and Environmental Engineering Shenzhen UniversityShenzhen518055China Chengdu institute of Organic chemistry Chinese Academy of SciencesChengdu610041China

In this study,we proposed a novel method that integrates density functional theory(DFT)with the finite field method to accurately estimate the polarizability and dielectric constant of polymers.Our approach effectively accounts for the influence of electronic and geometric conformation changed on the dielectric constant.We validated our method using polyethylene(PE)and polytetrafluoroethylene(PTFE)as benchmark materials,and found that it reliably predicted their dielectric constants.Furthermore,we explored the impact of conformation variations in poly(vinylidene fluoride)(PVDF)on its dielectric constant and polarizability.The resulting dielectric constants ofα-andγ-PVDF(3.0)showed excellent agreement with crystalline PVDF in experiments.Our findings illuminate the relationship between PVDF’s structural properties and its electrical behavior,offering valuable insights for material design and applications.

关键词： Dielectric constant PVDF Finite field DFT

Diatomic Fe-Co catalysts synergistically catalyze oxygen evolution reaction

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Nano Research 2024年第5期17卷 3794-3800页

作者： Tianmi Tang Jingyi Han Zhenlu Wang Xiaodi Niu Jingqi Guan institute of Physical chemistry College of ChemistryJilin UniversityChangchun 130021China College of Food Science and Engineering Jilin UniversityChangchun 130062China

The design of diatomic catalysts with uniformly dispersed metal atoms is expected to improve catalytic performance,which is conducive to the intensive comprehending of the synergistic mechanism between dual-metal sites for the oxygen evolution reaction(OER)at the atomic level.Herein,we design a strategy to immobilize bimetallic Fe-Co atoms onto nitrogen-doped graphene to obtain a diatomic catalyst(DA-FC-NG)with FeN_(3)-CoN_(3) configuration.The DA-FC-NG shows excellent OER activity with a low overpotential(η_(10)=268 mV),which is superior to commercial iridium dioxide catalysts.Theoretical calculations uncover that the excellent activity of DA-FC-NG is due to the interaction between Fe and Co diatoms,which causes charge rearrangement and induces the adsorption of intermediates on the Fe-O-Co bridge structure,thus improving the catalytic OER performance.This work is of great significance for the design of highly active diatomic catalysts to replace noble metal catalysts for energy-related applications.

关键词： oxygen evolution reaction diatomic catalyst FeN_(3)-CoN_(3) X-ray absorption spectroscopy(XAS)spectrum theoretical calculation

Upper-rim-modified thioether thiacalix[4]arene used for liquid-liquid extraction of Au(Ⅲ)and Pd(Ⅱ)in hydrochloric acid medium

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Chinese Journal of Chemical Engineering 2024年第2期66卷 110-118页

作者： Sheng Wan Rong Xie Jianhong Fan Kewen Tang Department of chemistry and Chemical Engineering Hunan Institute of Science and TechnologyYueyang 414006China

Gold(Au)and palladium(Pd)play an increasing role in the production and human life;Therefore,it is of great significance to study their recovery.A 5,11,17,23-tetra-ethylthio-25,26,27,28-tetra-hydroxyl thiacalix[4]arene(TCAET)was synthesized specifically for the capture of Au(Ⅲ)and Pd(Ⅱ)from HCl medium by liquid-liquid extraction.In a 0.1 mol·L^(-1)HCl medium,the transfer of Au(Ⅲ)and Pd(Ⅱ)from the aqueous phase to the organic phase was highly efficient,with a transfer ratio of 100%for Au(Ⅲ)and 98%for Pd(Ⅱ).Furthermore,the extraction equilibrium time for Au(Ⅲ)was just 5 min.Job's method data demonstrated that TCAET formed complexes with Au(Ⅲ)and Pd(Ⅱ)in a ratio of 2:3 and 1:1,respectively,during the extraction process.TCAET showed high selectivity toward Pd(Ⅱ)and Au(Ⅲ)over other competing metal ions.Moreover,both Au(Ⅲ)and Pd(Ⅱ)could be successfully stripped from the loaded organic phases with a 1.0 mol·L^(-1)thiourea in 0.5 mol·L^(-1)HCl and 0.5 mol·L^(-1)thiourea in 0.5 mol·L^(-1)HCl,respectively.Results obtained from five consecutive extraction-stripping cycles showed good reusability of TCAET toward Au(Ⅲ)and Pd(Ⅱ)recovery.The conclusion can provide a certain reference for thiacalixarene in the recovery of precious metal species.

关键词： Thiacalixarene Upper-rim modification Liquid-liquid extraction Precious metal Thioether

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Key role of electron accessibility at the noble metal-free catalytic interface in hydrogen evolution reaction

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Nano Research 2024年第4期17卷 2538-2545页

作者： Dongchen Han Nanxing Gao Yuyi Chu Zhaoping Shi Ying Wang Junjie Ge Meiling Xiao Changpeng Liu Wei Xing State Key Laboratory of Electroanalytical chemistry Changchun Institute of Applied ChemistryChinese Academy of SciencesChangchun 130022China School of Applied chemistry and Engineering University of Science and Technology of ChinaHefei 230026China Laboratory of Advanced Power Sources Changchun Institute of Applied ChemistryChinese Academy of SciencesChangchun 130022China Jilin Province Key Laboratory of Low Carbon Chemical Power Sources Changchun 130022China State Key Laboratory of Rare Earth Resource Utilization Changchun Institute of Applied ChemistryChinese Academy of SciencesChangchun 130022China

The reactant concentration at the catalytic interface holds the key to the activity of electrocatalytic hydrogen evolution reaction(HER),mainly referring to the capacity of adsorbing hydrogen and electron accessibility.With hydrogen adsorption free energy(ΔGH)as a reactivity descriptor,the volcano curve based on Sabatier principle is established to evaluate the hydrogen evolution activity of catalysts.However,the role of electron as reactant received insufficient attention,especially for noble metal-free compound catalysts with poor conductivity,leading to cognitive gap between electronic conductivity and apparent catalytic activity.Herein we successfully construct a series of catalyst models with gradient conductivities by regulating molybdenum disulfide(MoS_(2))electronic bandgap via a simple solvothermal method.We demonstrate that the conductivity of catalysts greatly affects the overall catalytic activity.We further elucidate the key role of intrinsic conductivity of catalyst towards water electrolysis,mainly concentrating on the electron transport from electrode to catalyst,the electron accumulation process at the catalyst layer,and the charge transfer progress from catalyst to reactant.Theoretical and experimental evidence demonstrates that,with the enhancement in electron accessibility at the catalytic interface,the dominant parameter governing overall HER activity gradually converts from electron accessibility to combination of electron accessibility and hydrogen adsorbing energy.Our results provide the insight from various perspective for developing noble metal-free catalysts in electrocatalysis beyond HER.

关键词： conductivity molybdenum disulfide catalytic interface electron accessibility hydrogen evolution charge transfer.

Bio-Based Rigid Polyurethane Foams for Cryogenic Insulation

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Journal of Renewable Materials 2024年第3期12卷 585-602页

作者： Laima Vevere Beatrise Sture Vladimir Yakushin Mikelis Kirpluks Ugis Cabulis Latvian State institute of Wood chemistry RigaLV-1006Latvia

Cryogenic insulation material rigid polyurethane(PU)foams were developed using bio-based and recycled feedstock.Polyols obtained from tall oil fatty acids produced as a side stream of wood biomass pulping and recycled polyethylene terephthalate were used to develop rigid PU foam formulations.The 4th generation physical blowing agents with low global warming potential and low ozone depletion potential were used to develop rigid PU foam cryogenic insulation with excellent mechanical and thermal properties.Obtained rigid PU foams had a thermal conductivity coefficient as low as 0.0171 W/m·K and an apparent density of 37-40 kg/m^(3).The developed rigid PU foams had anisotropic compression strength properties,which were higher parallel to the foaming direction.Moreover,the compression strength was also influenced by the type of applied bio-based polyol.The bio-based polyols with higher OH group functionality delivered higher crosslinking density of polymer matrix;thus,the mechanical properties were also higher.The mechanical strength of the foams increased when materials were tested at liquid nitrogen temperature due to the stiffening of the polymer matrix.The thermal properties of the developed materials were determined using differential scanning calorimetry,dynamic mechanical analysis,and thermogravimetric analysis methods.Lastly,the developed rigid PU foams had good adhesion to the aluminium substrate before and after applying cyroshock and an excellent safety coefficient of 4-5.Rigid PU foams developed using Solstice LBA delivered adhesion strength of~0.5 MPa and may be considered for application as cryogenic insulation in the aerospace industry.

关键词： Cryogenic insulation polyurethanes tall oil 4th generation physical blowing agents