Spin-crossover(SCO)materials that reversibly switch between high-and low-spin states have potential for the storage of spin state-relative information,and have gained much attention incorporating secondary physical properties,such as fluorescence and magneto-optical switching.In this study,we synthesized three octanuclear metal-organic cages(MOCs)using tetraphenylethylene-based luminophores,aldehydes,and Fe^(Ⅱ)salts,by subcomponent self-assembly approach,namely[Fe1]-[Fe3].By controlling the ligand-field strength and guest encapsulation,we finely tuned their SCO properties.Among them,MOC[Fe2]displayed nearly complete SCO behavior in the solid state,which is rare for high-nuclearity complexes.We also demonstrated the coupling of SCO with fluorescence emission in these MOCs by using isostructural Zn^(Ⅱ)complexes([Zn1]-[Zn3])as control experiments,for the first time.Theoretical calculations revealed the energy-transfer mechanism between fluorophores and SCOactive centers,which emphasizes the significant contribution of d-d transitions in the interplay between the occurrence of SCO and fluorescence emission.
Zhi-Kun LiuAlyona A.StarikovaYu-Xia LiKe SunMeng YuZi-Shuo YaoJun Tao
Interface engineering in device fabrication is a significant but complicated issue.Although great successes have been achieved by conventional physical in situ or ex situ methods,it still suffers from complicated procedures.In this work,we present a facile method for fabricating phthalocyanine(Pc)-based two-dimensional conductive metal–organic framework(MOF)films.Based on PcM-Cu(M=Ni,Cu,H_(2))MOF films,spin valves with a vertical configuration of La_(0.67)Sr_(0.33)MnO_(3)/PcM-Cu MOFs/Co were constructed successfully,and exhibited notably high negative magnetoresistance(MR)up to -22% at 50 K.The penetrated Co atoms coordinated with the dehydrogenated hydroxy groups in the MOFs resulting in an antiferromagnetic layer of the PcM-Cu-Co hybrid structure.Interestingly,a significant exchange bias effect was demonstrated at the PcM-Cu MOF/Co interface,beneficial for the MR behavior.Thus,our present study provides new insights into developing high-performance organic spin valves via de novo molecular design.
Potassium-ion batteries(PIBs)represent one of the most promising alternatives to lithium-ion batteries(LIBs),owing to their exceptional attributes such as high voltages,potent power capabilities,and cost-effectiveness.Nonetheless,challenges arise from the sluggish kinetics and significant volume expansion observed during the insertion/extraction of large-radii potassium ions,leading to subpar rate performance and considerable capacity degradation in potassium-ion batteries.Consequently,it becomes imperative to explore advanced anode materials exhibiting high electrochemical activity and robust structural stability.In this regard,the present review focuses on recent progress in metal-organic compounds(MOCs)as anode materials for potassium-ion batteries,systematically discussing their outstanding merits from the perspective of metal speciation.Additionally,the principal mechanism of K ion storage within relevant MOCs is presented.Furthermore,a comprehensive summary of existing drawbacks that hinder the broader application of MOCs-based materials is provided,along with proposed guidelines and strategies for addressing the inferior performance characteristics.This review serves to illuminate the development of MOCs-based anode materials for potassium-ion batteries and offers a valuable reference for future research endeavors.
Jinquan WenQian LiuLing BaiZhen-Dong HuangYanwen Ma
The development of circularly polarized luminescence(CPL)materials with high performance is signifi-cantly important.Herein,we develop a facial strategy for fabricating a CPL-active system by employing an achiral luminescent metal-organic cage(MOC)and chiral boron dipyrromethene(BODIPY)molecules.CPL is achieved by taking advantage of the radiative energy transfer process,in which BODIPY molecules act as energy acceptors and MOCs act as donors.The CPL performance(maximum luminescence dissymme-try factor up to±1.5×10^(−3))can be tuned by adjusting the ratio between MOCs and BODIPY.White-light emission with the CPL feature is obtained by using a ternary system including MOC,chiral BODIPY,and Rhodamine B.The present work provides a facile and universal strategy to construct a CPL-active system by integrating achiral luminophores and chiral molecules.
Zhao-Xia LianXue-Zhi WangChuang-Wei ZhouJiayu LiMing-De LiXiao-Ping ZhouDan Li
Alkaline water electrolysis is an environmentally friendly and promising approach to produce hydrogen.However,high cost,low efficiency,and poor stability are roadblocks to commercialization of electrocatalysts.This work aims to design and develop a highly efficient,durable,and cost-effective electrocatalyst toward water splitting through modifying metal–organic frameworks.The electrocatalytic performance and stability surpass those of noble metal benchmarks at high current density(1–10 A·cm^(−2)).Theoretical calculations and in situ Raman spectra reveal the electronic structure of the synthesized catalyst and the mechanism of the catalytic reaction process,which rationalizes that the high catalytic activity and stability at high current are attributed to the unique electronic structure of cobalt regulated by copper and the protection provided by carbon nanotubes formed in situ,respectively.In addition,this paper proposes that the desorption ability of the catalyst toward the products(H_(2)and O_(2)),rather than the adsorption ability toward the reactants(H^(+)or OH^(−)),is more important to the sustainable and stable electrochemical water splitting progress at high current density,which is a kinetic rather than thermodynamic dominating process.The findings provide alternative insights to design and employ high performance catalysts to fuel hydrogen production as a clean energy source to tackle the global energy crisis.
Metal-organic frameworks(MOFs)have favorable characteristics such as large specific surface area,high porosity,structural diversity,and pore surface modification,giving them great potential for development and attractive prospects in the research area of modern materials electrocatalysis.However,unsatisfactory catalytic activity and poor electronic conductivity are the main challenges facing MOFs.This review focuses on MOF-based materials used in electrocatalysis,based on the types of catalytic reactions that have used MOF-based materials in recent years along with their applications,and also looks at some new electrocatalytic materials and their future development prospects.
Photoresponsiveness of materials is critical to their tunability and efficiency in terminal applications.Photoresponsive metal-organic polyhedra(PMOPs)feature intrinsic pores and remote controllability,but aggregation of PMOPs in solid state hampers their photoresponsiveness seriously.Herein,we report the construction of a new PMOP(Cu_(24)(C_(16)H_(12)N_(2)O_(4))_(12)(C_(18)H_(22)O_(5))12,denoted as MOP-PR-LA),where long alkyl(LA)chains act as the intermolecular poles,propping against adjacent PMOP molecules to create individual microenvironment benefiting the isomerization of photoresponsive(PR)moieties.Upon ultraviolet(UV)-and visible-light irradiation,MOP-PR-LA is much easier to isomerize than the counterpart MOP-PR without LA.For propylene adsorption,MOP-PR has a low change of adsorption capacity(9.9%),while that of MOP-PR-LA reaches 58.6%.Density functional theory calculations revealed that PR in the cis state has a negative effect on adsorption,while the trans state of PR favors adsorption.This work might open an avenue for the construction of photoresponsive materials with high responsiveness and controllability.
Long ZhengPeng TanQian SongSheng-Tao WangMin LiXiao-Qin LiuLin-Bing Sun
In view of novel materials in the field of lithium metal batteries(LMBs), metal-organic frameworks(MOFs) have attracted extensive research interest owing to their controllable pore size, unsaturated metal sites and multifunctional organic groups. A variety of MOFs have been elaborately calculated and synthesized to be applied as separator coating, electrolyte modulators and solid-state electrolyte fillers in LMBs. In this mini-review, we summarize the mechanism of MOFs to limit the migration of anions, improve the Li-ion transference number and prolong the lifespan of LMBs. Suitable pore structure of MOFs can physically restrict the movement of Li^(+). Unsaturated metal sites can adsorb anions by electrostatic interaction. In addition,multifunctional organic functional groups that limit the migration of anions are discussed. Finally, the key challenges and perspectives in the development direction of MOFs-based separators and electrolytes are further elaborated.
