| Coordination polymers have broad application prospects in the fields of molecular recognition,magnetism and gas adsorption and separation due to their advantages of easy structure adjustment and functionalization.However,the self-assembly process of coordi--nation polymers is affected by many factors,therefore,reasonable design and construction of coordination polymers with structural diversity and specific functional is not only a difficult point,but also a key problem that limits their application.In this paper,a series of coordi-nation polymers with novel structures and excellent performance are constructed based on H5L1 and H5L2 aromatic pentacarboxylic acids and transition metal salts under solvent heat conditions.Meanwhile,the structures of these coordination polymers were characterized by X-ray single crystal diffraction,elemental analysis,IR spectroscopy and thermogravimetric analysis.In addition,the fluorescence properties,magnetic properties and gas adsorption properties of partial coordination polymers were studied.The main research contents and results are as follows:（1）Sixteen coordination polymers were synthesized based on H5L1 and H5L2 with transition metal ions.Their chemical formulas are listed below:{[Zn5（L1）2（μ3-OH）2]·2H3O·2CH3CN·0.5H2O}n（1）,{[Cd2（L1）（H2O）2]·0.5C10H10N2·4.75H2O}n（2）,{[Co3（L1）2（μ2-H2O）2]·4NH4·5CH3CN·3.5H2O}n（3）,{[Co2.75（L1）（H2O）3.5（μ3-OH）]·1.5NH4·3CH3CN·4H2O}n（4）,{[Zn2（L1）（4,4′-bipy）0.5（H2O）]·0.5（4,4′-bipy）·4H2O}n（5）,{[Cd2（HL1）（1,4-bipb）0.5（CH3CN）（H2O）]·4H2O}n（6）,{[Co3（L1）（4,4′-biib）（H2O）（μ3-OH）]·EtOH·5H2O}n（7）,{[Zn2（HL1）（1,4-bibb）2]·5H2O}n（8）,{[Zn5（L2）2（H2O）5]·3DMA·2.5EtOH·4.5H2O}n（9）,{[Cd5（L2）2（H2O）6]·DMA·2EtOH·3.5H2O}n（10）,{[Co2（HL2）（H2O）4（μ2-H2O）]·3.5H2O}n（11）,{[Cu2（L2）（1,4-bipb）2]·H2N（CH3）2}n（12）,[Co（H3L2）（1,4-biib）]n（13）,{[Ni5（L2）2（1,4-bibb）2（H2O）4（μ3-OH）2]·2H2N（CH3）2·3DMA·3H2O}n（14）,{[Co2（HL2）（4,4′-bibb）2]·0.5EtOH·2H2O}n（15）,{[Cd（HL2）0.5（4,4′-bibb）1.5]·1.5H2O}n（16）。X-ray single crystal diffraction analysis showed that these coordination polymers presented a variety of structures.（2）By comparing the structure of each coordination polymer,it is found that the pH value,metal ions and ligand configuration of the system play a very important role in the structure of coordination polymers.In this work,two 3D coordination polymers 3 and 4 with different structures were constructed by changing the pH value of the reaction system,and the structural analysis of them showed the pH value of the system would affected the coordi--nation mode of ligands and the composition of SBUs,resulting in different structures.For another example,under different reaction conditions of metal salts,coordination polymers15（3D）and 16（2D）with completely different structures were constructed,which was caused by different coordination properties of metal ions.In addition,the coordination polymers were characterized by powder X-ray diffraction,IR spectroscopy and thermogravimetry,and the results showed the coordination polymers had high phase purity and good thermal stability.（3）In order to reveal the relationship between structures and properties of coordination polymers,the related properties were studied as follows:（1）The fluorescence properties of zinc and cadmium coordination polymers were studied.The results showed that they have high sensitivity and selective recognition to Fe3+,Hg2+,CrO42-and Cr2O72-ions in aqueous solution.In addition,the fluorescence quenching mechanism was investigated through a series of experiments.and it was speculated that the fluorescence quenching might be caused by the competitive absorption and weak interaction between the coordination polymer and the detector.（2）The magnetic properties of copper-based,nickel-based and cobalt-based coordination polymers were tested.The results of the DC susceptibility study showed that there were anti--ferromagnetic interactions between metal ions in coordination polymers 3,4,7,11,12,13and 15,while there were ferromagnetic coupling interactions between Ni（II）ions in 14.The comparison showed that theχMT values of all cobalt-based coordination polymers were higher than the theoretical values,which may be caused by the spin coupling of Co（II）ions.In addition,the AC magnetic susceptibility datas show that coordination polymers 3,4,7,11 and15 have frequency dependence and slow delay of magnetization,which may be caused by the net magnetic moment of the magnetic structure of coordination polymers and the magnetic anisotropy of Co（II）ions.（3）The adsorption properties of N2,H2,CO2 and CH4 were studied for coordination polymers with high porosity.The results show that the adsorption performance of coordi--nation polymers for N2,H2 and CO2 were better than that of CH4.In addition,the separation effects of coordination polymers for natural gas（0.05/0.95）and coal mine tunnel gas（0.5/0.5）were simulated and analyzed by the ideal adsorption solution theory（IAST）model and the results showed that the separation effect was good.Finally,The adsorption heat of gas were calculated by using virial formula（virial-type）,and the results showed the adsorption heat of some coordination polymers to CO2 were higher,indicating that there was a strong force between them and CO2,and the adsorption amount of CO2 was also larger.The above results may be related to the pore size of coordination polymer,the size and configuration of gas molecules and the interaction between the host and the object.In a word,the studies of this work can provide a certain experimental basis for the construction of fluorescent,magnetic,adsorption and separation materials.In addition,the properties of the coordination polymers show that they have potential applications in fluorescent probe,magnetic,gas adsorption and separation,and the results also provides important guidance for the design,construction and application of specific functional coordination polymer materials. |
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