Research On The Synthesis Of A New Type Of Total Nitrogen Pentaazole Ion Materials

All-nitrogen cyclo-N₅^-compounds are a newly emerging class of energetic materials and have attracted significant attention in recent years.The synthesis and property studies of new cyclo-N₅^-compounds have been a hot topic in the field of energetic materials.Compared with traditional CHNO-based energetic materials,all-nitrogen cyclo-N₅^-compounds can release a large amount of energy in the decomposition reaction of converting N-N and N=N bonds into N2（N=N bond）.In addition,the decomposition products of cyclo-N₅^-compounds are more environmental-friendly and have the characteristic of low characteristic signals.Despite excellent properties,the synthesis of stable cyclo-N₅^-compounds has been a worldwide challenge for a long time.In 2017,the successful synthesis and stabilization of isolated cyclo-N₅^-compound was achieved at room temperature,which represents a significant breakthrough in the field of all-nitrogen compounds.This dissertation will focus on the synthesis of new cyclo-N₅^-compounds.Two new cyclo-N₅^-compounds were successfully obtained through modified synthetic methods,and their structures and properties were well characterized and evaluated.This will provide a guidance for researchers in the field of energetic materials.The content of this dissertation includes three parts:1.A brief review on all-nitrogen compounds and cyclo-N₅^-materialsThis part briefly introduces the research background of all-nitrogen compounds and the development history of cyclo-N₅^-materials.Since 1772 that humans discovered the first all-nitrogen compound N2,the all-nitrogen compounds have experienced the rapid development.In 2017,the researchers from China have achieved new significant breakthroughs in the field of cyclo-N₅^-compounds.The cyclo-N₅^-anion can coordinate or pair with a variety of metal and non-metal ions.It has opened the door of cyclo-N₅^-chemistry.2.Synthesis of zeolite cyclo-N₅^-material（MPF-1）with nano-caged structuresThe synthetic route of cyclo-N₅^-compounds was improved and optimized.Using 2,6-dimethyl-4-pentazolyl phenol as the raw material and in the presence of m-chloroperoxybenzoic acid（m-CPBA）and ferrous glycinate[Fe（Gly）2]as the catalyst,the C-N bond of cyclo-N₅^-anion was successfully cut and the intact cyclo-N₅^-was separated and stabilized at room temperature through hydrogen bonding interactions.Single crystals of MPF-1 were grown from the aqueous solution of cyclo-N₅^-sodium salt at ambient temperature for several days.MPF-1 has 3-dimensional zeolite pores MOFs structure,in which each N atom on cyclo-N₅^-anion is bonded to five adjacent sodium ions.The zeolite-like framework of MPF-1 features two types of nanocages,that is,Na₂₀N₆₀ and Na₂₄N₆₀.The decomposition temperature of MPF-1 is up to 129.4℃.which is higher than that of most reported cyclo-N₅^-compounds.3.Synthesis of bimetallic cyclo-N₅^-framework[LiNa（N₅）₂（H₂O）₄]·H₂OA novel bimetallic cyclo-N₅^-framework[LiNa（N₅）₂（H₂O）₄]·H₂O featuring helical chains was synthesized.It has a 3-dimensional supramolecular structure and the adjacent{Li（H₂O）2（N₅）5} trimers form a left-handed and right-handed helical chain structure through O-H…N hydrogen bonds.Hirshfeld surface analysis and 2D fingerprint spectra revealed that the hydrogen bond interactions of N…H and O…H in the crystal structure significantly improve the stability of[LiNa（N₅）₂（H₂O）₄]·H₂O.The TG-DSC results showed that it started to decompose at T=106.1℃.This work provides a solid theoretical foundation for exploring the coordination chemistry of cyclo-N₅^-anion.