Design,Synthesis And Fluorescence Sensing Properties Of Mofs Based On Functionalized Polycarboxylic Acid

Metal-organic frameworks?MOFs?,as inorganic-organic hybrid material,have various topological structures and can be systematically pre-designed for their structural components compared to inorganic porous materials.The self-assembly of inorganic and organic fluorescent nodes into porous MOFs has allowed us to generate unique luminescent platforms for fluorescence sensing properties.Firstly,based on guest molecules serve as recognition site,we demonstrate that the good control of solvothermal reaction conditions of different coordination modes of transition metal ions(Mn²⁺,Co²⁺,Ni²⁺,etc.)and polycarboxylic acid,depending on amides solvent molecules.Secondly,based on major framework with functional groups as recognition site,the MOFs were synthesized using a serious of the different functional groups ligand.Finally,based on dense of uncoordinated carboxyl oxygen atoms as recognition site,the MOFs were used to synthesize MOFs according to the mixed-ligand strategy of length mismatched carboxylic acid ligands.The research contents are as follows:?1?It is noteworthy that the both?3,6?-connected structure of the complex 1 and 2 have been used to solvothermally synthesize.Both complex 1 and 2 in which guest molecules serve as recognition site can quickly and sensitively identify Fe³⁺.The fluorescence quenching constants K_SV were 5463 M^-1 and 10193 M^-1,respectively.In addition,they have high sensitivity,the detection limits LOD were 0.0026 mM and 0.0020 mM,respectively.?2?The five metal-organic frameworks?MOFs?derived from a serious of the ligands H₄BPTC?3,3',5,5'-biphenyltetracarboxylic acid?inserted three different functional groups between the two benzene rings of H₄BPTC:ligand H₄BNTC?bis?3,5-dicarboxyphenyl?azo?inserted of the azo bond?-N=N-?,inserted m-phenyl group?m-C₆H₄?lead to H₄TPTA?1,3-di?3',5'-dibenzoic acid?benzene?,inserted p-phenyl group?p-C₆H₄?to H₄TPTC?p-terphenyl-3,3'',5,5''-tetracarboxylic acid?ligand,which were synthesized with a major framework with functional groups as recognition site for fluorescence sensing.The sensing experiments show that both complexes 3 and 6 can quickly and sensitively identify Fe³⁺.The fluorescence quenching constants K_SV of 3 and 6 were 9181 M^-1 and 7233 M^-1,respectively,and the detection limits LOD were 0.0026 mM and 0.0029 mM,respectively.According to the DFT method,the structure of the fluorescent molecule H₄BPTC and H₄TPTA was optimized.The spin density distribution shows that the mechanism of fluorescence quenching is mainly the transfer of electron from the benzene ring on the ligand to Fe³⁺,which leads to the fluorescence quenching.?3?Two unique isostructural anion channel-type metal-organnic frameworks?MOFs?,with molecular formula{[Et₂NH₂][M_1.5?Ina??HIna???₂-OH??TPTC?_0.5]}_n?M=Co-Complex 8,Ni-Complex 9?were synthesized under solvothermal conditions using mixed ligands H₄TPTC,isonicotinic acid?HIna?and metal ion Mn²⁺.Its 1D pore wall is decorated with high-density uncoordinated carboxyl oxygen atoms,which can serve as recognition sites.Complex 8 and 9display excellent sensing Fe³⁺properties.The fluorescence quenching constants K_SV of complexes 8 and 9 were 4069 M^-1 and 5263 M^-1,respectively,and the detection limits LOD were 0.0034 mM and 0.0037 mM,respectively.The recognition mechanism of complexes 8and 9 on Fe³⁺was calculated by Gauss.The calculation results show that the fluorescent ligand TPTC^4-is oxidized to non-fluorescent cationic radicals due to the strong oxidizing property of Fe³⁺,resulting in fluorescence signal quenching.