Syntheses,Pore Modification And Properties Of Metal Organic Frameworks Based On Rigid Carboxylates Ligands

Metal-organic frameworks?MOFs?,also named coordination polymers,are built from inorganic metal ions coordinated by organic linkers.Based on the geometric structure of organic ligands and coordination mode of inorganic metal ions,we can design and adjust the structure of different polymers.With high ultra porosity?some MOFs can up to 94%?and specific surface area?may achieve 7140m²/g?,the porous materials are playing an increasingly important role in storage and separation,sensor,proton conduction,drug delivery and other fields.We synthesized three fluorene derivative ligands,which are 9-fluorenone-2,7-dicarboxylate?H₂FODC?,S,S-dioxodibenzothiophen-3,7-dicarboxylic?H₂DTDAO?,9-fluorene-2,7-dicarboxylate?H₂FDC?.Using them as bridging-linkers,under the help of other auxiliary ligands,we synthesized nine compounds under the self-assembly with Zn?II?/Cd?II?.Not only analyzed the structure of the compounds,we also studied the practical application of some functionalized polymers in gas adsorption,dye adsorption and separation.The main contents are listed as follows:1.Studies on the pore modification of porous materials and its effect on the adsorption.With the crystal engineering strategy,we constructed three isomorphic compounds?1-3?with different pore surface successfully under the coordination of fluorene derivative ligands with Zn?II?.Through the structural analysis of the three porous materials,we found both the carbonyl and sulfone groups in 1-2 hanged into the channel.In order to explore the effect of pore modification on the adsorption behavior,we have done the following research:?1?Under the same condition,N₂ and CO₂ adsorption and desorption isotherms of compounds 1-3 were measured.The result showed that 2 could absorb the most CO₂ though with the smallest pore volume.It speculated there exited strong affinity between sulfone and CO₂ molecule,this also proved the effectiveness of the ligands modification.?2?Experiments showed compound 1 had unique selective adsorption behavior on cationic dye in aqueous solution,which is attributed to the electrostatic interaction between carbonyl and the cationic dyes.Therefore,compound 1 has potential application in the adsorption and separation of dyes in aqueous environment.In addition,we studied the dynamic,adsorption isotherm and recycle behaviors of compound 1.The result proved that adsorption of the three dyes all belong to pseudo-second-order kinetic model;MB and RhB is Langmuir adsorption,while Freundlich adsorption for CV.2.Two-dimensional coordination polymers and properties analysis tuned by4,4-azo pyridine?azpy?.Using 4,4-azpy as auxiliary ligand,the three fluorene derivative ligands as bridging ligands,we synthesized three 2D compounds?4-6?based on the self-assembly with Zn?II?under solvothermal method.Compounds 4 and 6 are constructed first through 2D?2D interpenetration,then parallel acculation to form 3D constructure.Compound 5 is constructed only through the parallel acculation of 2D structure.We also measured the fluorescence emission spectra of the three complexs.3.One-dimensional compounds tuned by chelating ligands 2,2?-bpy and phen.We synthesized three 1D supermolecular compounds?7-9?under the diffusion method,taking Cd?II?as the metal center,deprotonated H₂FODC and H₂FDC as bridging-ligands,2,2?-bpy and phen as auxiliary ligands.Compound 7 is 1D composing of double chain.Compound 8 and 9 are stacked in the same way.They all belong to 1D zigzag except the difference of terminal ligands decorated around the Cd?II?.