The Structure Regulation And Properties Of Coordination Polymers Based On Symmetric Polycarboxylic Acid Ligands

At present,coordination polymers as a new inorganic-organic hybrid materials have received wide attention due to their unique structure,which have already been studied extensively in the fields of fluorescence probe,gas adsorption,photocatalysis and magnetism and so on.In this study,we have synthesized eighteen novel coordination polymers based on3,5-di（2’,5’-dicarboxylphenyl）benozoic acid（H₅L）and 3,5-di（2’,5-dicarboxylphenyl）pyridine（H₄L）and transition metal ions under hydrothermal/solvothermal conditions,and characterized by X-ray single-crystal diffraction analysis,IR spectrum analysis,thermogravi-metric analysis and powder X-ray diffraction analysis.The behaviour of luminescent sensing anions and cations or small organic molecules for some complexes and gas adsorption experiments for CO₂、CH₄、H₂、N₂ of partial complexes have been studied.Magnetic testing determined the electron states of metal ions for some complexes.1.We chose a V-shaped symmetric polycarboxylic acid ligand 3,5-di（2’,5’-dicarboxylphenyl）benozoic acid（H₅L）and Cd（Ⅱ）/Ni（Ⅱ）to construct three MOFs{[Cd₃（L）（OH）（H₂O）₃]_n·2H₂O}（1）,{Cd₅（L）₂（H₂O）₉}_n（2）and{Ni（H₃L）（H₂O）}_n（3）.The synthesis procedure for complexes 1 and 2 was the same except for different solvent and pH value.Complex 1 is a porous 3D structure with the trinuclear[Cd₃（OH）（COO）₅]SBUs,complex 2 displays a 3D framework structure with the pentanuclear[Cd₅（COO）₁₀（H₂O）₉]SBUs,Complex 3 is a 1D infinite chain structure with[Ni（μ₂-H₂O）（μ₂-COO）（μ₁-COO）₂]_n SBUs.The structural comparisons of complexes 1-3 show that solvents and metal ions play a decisive role in the regulation of structure.Furthermore,fluorescence measurements indicated that 1 show potential application in the detection for Fe³⁺,CrO₄^2-and Cr₂O₇^2-ions in aqueous solution.Gas adssorption property exhibits that complex 1 has better hydrogen storage performance,and has a certain application prospect in hydrogen storage.2.A series of auxiliary ligands were added on the basis of original experiment,which have been constructed twelve MOFs based on 3,5-di（2’,5’-dicarboxylphenyl）benozoic acid（H₅L）and Cd/Zn/Co/Ni ions:{[Cd₂（HL）（4,4-bipy）（H₂O）]_n·H₂O}（4）,{Zn₂（HL）（phen）}_n（5）,{Zn₂（HL）（2,2-bipy）}_n（6）,{[Pb₂（HL）（phen）]_n·2H₂O}（7）,{Cd₂（L）（1,4-bib）（NH₄）}_n（8）,{Ni₃（H₂L）₂（4,4-bpyb）₂}_n（9）,{[Ni（H₃L）（4,4-bipy）_1.5（H₂O）₄]·6H₂O}_n（10）,{[Ni₂（HL）（1,4-bibb）（H₂O）]·（CH₃CN）·（H₂O）}_n（11）,{[Co₂（HL）（1,4-bibb）（H₂O）]·（CH₃CN）·（H₂O）}_n（12）,{[Co₂（HL）（2,2-bipy）]·（H₂O）}_n（13）,{[Co₃（L）（OH）（H₂O）₄]·（1,4-bmib）}_n（14）and{[Co₆（L）₂（OH）₂（4,4-biyb）]·2（CH₃CN）·3（H₂O）}_n（15）.Besides,the synthesis process of complex 8 was similar to that of 1 except for the addition of auxiliary ligand.X-ray single crystal diffraction analyses showed that they were chain structure,sheet structure or skeleton structure.The structural comparisons of complexes show that the auxiliary ligands with different lengths and flexibility also play a important role in the structure.In addition,fluorescence measurements reveal that 4,5,6,7,and 8 show potential application in the detection for Fe³⁺or Cu²⁺,CrO₄^2-or Cr₂O₇^2-ions in aqueous solution.Gas adsorption property exhibits that complex 8 has better hydrogen storage performance.3.We chose a 3,5-di（2’,5-dicarboxylphenyl）pyridine（H₄L）ligand and Cd（Ⅱ）to constructthreeMOFs{[Cd₂（L）（1,4-bpmb）（H₂O）]_n·H₂O·0.5EtOH}_n（16）,{[Cd₂（L）（1,3-bib）（H₂O）]_n·H₂O}_n（17）and{[Cd₂（L）（1,3-btyb）_0.5（H₂O）（DMA）]·H₂O}_n（18）.16and 17 are isostructural,which display a porous 3D structure,18 is 3D structure with[Cd₂（COO）₄N₂]SBUsand[Cd₂（COO）₄（H₂O）₂N₂]SBUs.Moreover,fluorescence measurements display that 16 has potential application in the detection for acetone and Fe³⁺.Gas adsorption property exhibits that 16 has higher CO₂ adsorption capacity than CH₄,and has a certain application prospect in capture CO₂.