| Framework materials such as covalent organic frameworks(COFs)and metal organic frameworks(MOFs)with advantages of controllable,adjustable pore structure,high crystallinity,and large specific surface area,which can be used in the fields of gas storage and separation,catalysis,electronics,biomedicine and energy.With the excellent application prospects,the development of framework materials has received great attention.At present,the research of framework materials mainly focused on the synthesis and performance of COFs and MOFs.Most of them are constructed with organic cyclic compounds as buliding blocks.However,only few researches reported framework materials with inorganic ring as the building unit.The phosphazene ring is a typical inorganic ring,which is only composed of phosphorus and nitrogen elements with special chemical properties.In this thesis,phosphonitrilic chloride trimer(PCT)was selected as the reaction unit to prepare three new types of inorganic phosphazene framework materials:N3P3,Na3(PO2NH)3·4H2O and KNa2(PO2NH)3·2H2O through the rational chemical design,and their performances in magnetism and piezoelectricity were further studied.The main contents are shown as follows:1.According to the active chemical properties of PCT,copper was selected as the substrate and catalyst,an inorganic two-dimensional sheet-like phosphorous nitride(N3P3)was synthesized through the interfacial polymerization,the optimized synthesis temperature and time was 180?and 36 h,respectively.This synthesis process is facile and efficient,and a small amount of copper salt was produced.The morphology of the two-dimensional layered stacking and crystal structure of N3P3 were revealed.The magnetic properties of N3P3 were studied.It exhibits a typical paramagnetism between 50 K and 300 K by its Curie-Weiss behavior,a Curie transition temperature at 7.5 K and a weak ferromagnetic property at 1.8 K with the coercive field(Hc)of 375 Oe and residual magnetization(Mr)of 0.0657 emu g-1,respectively,which leads its potential applications in the field of spintronics.2.Owing to the hydrolysis characteristics of PCT,it can be hydrolyzed by NaOH in a two-solvent system(DMF/H2O).The addition of NaOH not only can promote the hydrolysis of PCT;but also the Na+can coordinate with the hydrolysate,so as to form Na3(PO2NH)3·4H2O crystals on a large scale.The optimized crystallization condition is shown as follows:oil-water ratio is 1/1,the temperature is 40?,and the reactant molar ratio(PCT/NaOH)is 1/6.The crystal structure of Na3(PO2NH)3·4H2O was revealed by single crystal X-ray diffractometer(XRD).Na3(PO2NH)3·4H2O has a good piezoelectric activity due to its excellent crystallinity and asymmetric crystal structure,which lead it to be used as the piezoelectric active filler.The PNONa-PVDF film was produced by electrospinning of the mixture of crystals and polyvinylidene fluoride(PVDF).When the mass content of Na3(PO2NH)3·4H2O was 10%,the piezoelectric output of PNONa-PVDF film was 3.89 times higher than that of the pure PVDF film.The piezoelectric nanogenerator(PENG)prepared by the composite film can be effectively applied for energy harvesting with a maximum power density of 0.5?W cm-2.In addition,compared to conventional piezoelectric single crystals and piezoelectric ceramics,Na3(PO2NH)3·4H2O has advantages such as no heavy metal elements,simple preparation and cost-effeciency.3.Based on the synthesis of Na3(PO2NH)3·4H2O crystals,the alkali source was changed from NaOH to KOH.It was found that the addition of Na Cl as an auxiliary salt promotes to yield bimetallic KNa2(PO2NH)3·2H2O single crystal with a triclinic symmetry.The electrospun PNONaK-PVDF composite film with a piezoelectric activity was obtained by adding 2.5%KNa2(PO2NH)3·2H2O into PVDF.Its piezoelectric performance output was 60%higher than that of pure PVDF film.In this paper,three kinds of pure inorganic phosphazene framework were prepared based on PCT,and their magnetic and piezoelectric performances were further explored.This work may provide a new idea for expanding the types,synthetic design and application of inorganic framework materials. |
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