Design Of MOF Derivatives And Their Microwave Absorption Properties

With the rapid development of modern technology,the application of electromagnetic waves has become more and more extensive,and electromagnetic waves have become a source of pollution that cannot be ignored.In order to solve the pollution and interference of electromagnetic waves,researchers are committed to synthesizing high-performance electromagnetic wave absorbing materials to achieve effective attenuation of electromagnetic waves.Composite materials with both dielectric loss and magnetic loss can meet the actual requirements of absorbing materials for thinner thickness,lighter weight,stronger absorption,and wider frequency band.Metal-organic Framework(MOF)is a framework structure formed by the combination of metal ions and organic ligands.It has the advantages of high porosity and light weight.It is an ideal precursor for absorbing materials.In this paper,different metal-organic frameworks are used as precursors,and magnetic/dielectric composite materials with excellent absorbing properties are prepared through modification,and the absorbing mechanism is systematically studied and analyzed.The main parts of the paper are as follows:(1)Using ZIF-67 as the precursor,through surface modification of ZIF-67 and high temperature annealing in Ar atmosphere,a Co-C@C composite material with a hollow structure was successfully synthesized.When the absorber thickness is 2.5 mm,the minimum reflection loss(RLmax)is-58.1 dB,and its effective absorption bandwidth(EAB)is 4.56 GHz(9.36-13.92 GHz).Subsequent research proves that the excellent microwave absorption performance of Co-C@C is due to its good impedance matching.This unique hollow structure Co-C@C composite material may have the potential as a high-efficiency microwave absorption material.(2)Non-magnetic MOFs often do not have excellent absorbing properties due to the lack of magnetic loss.By introducing magnetic elements into the non-magnetic MOF,it is converted into a magnetic carbon-based composite material.Through the combined effect of dielectric loss and magnetic loss,excellent microwave absorption performance is obtained.With cubic ZIF-8 as the precursor and FeSO4 as the magnetic source,the Fe/Zn nanocomposite was obtained by annealing at high temperature in Ar atmosphere for 3 h.When the mass load is 40 wt%,at the thickness of 3.3 mm and the frequency of 8.48 GHz,the Fe/Zn nanocomposite has the minimum reflection loss of49.7 dB.The synergistic effect of the dielectric component and the magnetic component increases the attenuation ability of the material to electromagnetic waves,improves the impedance matching of the material,and greatly improves the electromagnetic wave absorption performance of the material.Subsequent researches show that the introduction of magnetic components into non-magnetic MOF is a feasible modification scheme,which provides a reference for the modification of MOF absorbing properties.