Design Of Column-supported Metal-organic Frameworks And Fluorescence Detection Of Nitro Compounds

Metal-organic frameworks（MOFs）,as a kind of multifunctional structural design plateform composed of metal ions/clusters and organic linkers,exhibit excellent crystallinity,adjustable pore size,and structural diversification.They have become one of the key areas of research and development in the last 25 years.The existing detection technology is limited by the shortcomings in cost,selectivity and application conditions.MOFs,as high-potential chemical sensors,have thus exhibited great potential in detecting hazardous chemicals such as explosives and pesticides.The challenge is how to design a sensitive and efficient fluorescent MOF sensor for the detection of specific explosives.This thesis aims to introduce specific fluorophores and active sites into the three-dimensional structure of MOFs through design and facile synthesis of ligands,so as to realize the detection of new N-heterocyclic explosives and traditional nitroaromatic compounds.The specific content as follows.（1）In Chapter 2,we have designed an organic ligand with a large dipole moment（2,7-dipyridyl-9-fluorenone）and synthesized through a simple organic reaction.By introducing 4,4-diphthalic acid（H₂BPDC）as an auxiliary ligand,we have successfully prepared a new type of triple penetration structuted Zn-based MOF（Zn MOF-1）with high crystallinity,high specific surface area,and rich hydrogen bonds.The MOF exhibit a fluorescence emission spectrum of450-650 nm.Utilizing its excellent fluorescence performance,Zn MOF-1 has realized the detection of emerging energetic compounds of 1,1-diamino-2,2-dinitroethylene（FOX-7）with a detection limit of 0.14 ppm,together with the highest fluorescence quenching constant is3.22×10⁴ M^-1.Density functional theory and molecular simulation results show that hydrogen bonding and dipole-dipole interaction strengthen the host-guest interaction between Zn MOF-1and Triaz FOX,thereby improving detection sensitivity.（2）In Chapter 3,We modified the side chain of the dioxolane ring on theπ-conjugated carbazole unit to introduce oxygen active sites and improve molecular solubility to further reduce the difficulty of synthesis,and synthesize Zn MOF-2 with H₂BPDC as an auxiliary ligand.This material has the characteristics of hydrogen bond active sites,conjugated structure,strong fluorescence,and the emission spectrum covers 375-575 nm.The detection results of different nitro compounds show that Zn MOF-2 has better detection sensitivity for 4-NA than Triaz FOX,and can distinguish different nitroaniline isomers.The detection limits for 4-NA are respectively70 ppb.Its excellent detection ability comes from the unique match between the UV absorption spectra of nitroaniline isomers and the MOF emission spectra and the hydrogen bonding effect compared to other nitro compounds,which provides an additional driving force for detection.In summary,we have designed and synthesized simple ligands to construct Zn-based MOF materials for explosive detection.The results show that through reasonable ligand structure design,the spectral matching and electrostatic interaction between the sensor and the analyte can be changed,which has guiding significance for the design of highly sensitive luminescence sensors of highly polar nitro compounds.