| Metal-organic frameworks?MOFs?are self-assembled by metal ions or metal clusters and organic ligands,combining to form a series of materials with novel structures and multifunctions.This type of material has large specific surface area,different pore size distribution,controllable morphology,diversity of structures,and high thermal stability,thereby giving it potential applications in different fields.With good application prospects and easily adjustable organic functional groups and metal nodes,more and more MOFs materials have been prepared.But the application of MOFs is far from enough.How to design and obtain the target products we need is still challenging.It is reported that the[?CH3?2NH2]Mn?HCOO?3 crystal with magnetic metal ion of Mn2+was prepared by a solvothermal method in the Institute of Physics.The paraelectric-ferroelectric phase transition temperature happens at 185 K and the paramagnetic-antiferromagnetic phase transition temperature is 8.5 K.This discovery opened up a new research direction for multiferroic materials.Multiferroic magnetoelectric materials have the ferroelectric and ferromagnetic ordering,which offers possibilities for the design new devices.There is a coupling between magnetic and electrical order.Based on this,the iron-doped[?CH3?2NH2]Mn?HCOO?3 crystals were successfully grown.The effect of Fe-Mn superexchange is expected to increase the magnetic properties of the material.In addition,the acquisition of high-quality single crystals is conducive to the study of the intrinsic physical properties.The doping concentration is 0:10,1:9,2:8 and 3:7 in order of Fe/Mn molar ratio.Which were recorded as[?CH3?2NH2]Mn?HCOO?3?Pure Mn?,[?CH3?2NH2]Fe0.1Mn0.9?HCOO?3(Fe0.1Mn0.9),[?CH3?2NH2]Fe0.2Mn0.8?HCOO?3(Fe0.2Mn0.8),[?CH3?2NH2]Fe0.3Mn0.7-?HCOO?3(Fe0.3Mn0.7).The growth conditions of the four different crystals were explored,and the samples were characterized by structure,phase analysis and morphology analysis.The study focused on the effects of different concentrations of iron doping on the magnetic properties of[?CH3?2NH2]Mn?HCOO?3 crystals;in addition,because the crystals had different pore structures,the electrochemical performance of the samples were studied.The experimental results and conclusions are as follows:1.Using hydrothermal method,FeCl2·4H2O and MnCl2·4H2O as metal ion ligands,N,N-dimethylformamide aqueous solution as the reaction heat solvent successfully prepared the chemical formula[?CH3?2NH2]X?HCOO?3?X=Fe/Mn?metal organic framework material.Through a large number of experiments,it has been found that as the doping concentration of iron increases,crystal growth crystals become more and more difficult.The prepared crystal samples were characterized by X-ray diffraction?XRD?.The crystals were found to grow mainly in the[012]direction;Raman spectroscopy?Raman?determined the vibrational modes of the internal molecules;Scanning Electron Microscopy?SEM?and the Energy Dispersive Spectrometer?EDS?analysis were used to observe the surface morphology,particle size and the ratio of Fe/Mn of the content.2.The magnetic properties of the four crystals were carried out through the magnetic hysteresis loop,zero field cooling and field cooling,and Curie-Weiss fitting analysis.It was found that with increasing iron doping concentration,the magnetization of the samples is enhanced,and the magnetic properties of Fe0.3Mn0.7are different from those of the three crystal samples with low iron doping concentration.It has three magnetic transition temperatures:118.3 K,40.3 K,and 8.3K.This is due to the presence of three molecular chains,-Fe-O-C-O-Fe-,-Fe-O-C-O-Mn-,and-Mn-O-C-O-Mn-,contributing to the magnetic transition.3.In terms of electrochemical performance,cyclic voltammetry tests,galvanostatic charge and discharge tests,alternating current impedance tests,and cycle life tests were sequentially performed.The results showed that Fe0.1Mn0.9exhibited better electrochemical characteristics than other samples.At a current density of 0.01 A g-1,the specific capacitance is 167.95 F g-1,and after 100 cycles,its capacitance retention rate is about 70%. |
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