Synthesis,Structure And Capacitance Performance Of MOFs Based On Aromatic Tetracarboxylic Acid

Metal organic frameworks（MOFs）,large specific surface area and rich pore structure,have very strong potential in the field of supercapacitors.The usage of the four ligands,3,3′,5,5′-biphenyltetracarboxylic acid（L1 = H₄BPTC）,5-（2-（（3,5-dicarboxybenzyl）oxy）ethoxy）isophthalic acid（L2 = H₄PDTA）,5,5’-（1,4-phenylenebis（methyleneoxy））disophthalic（L3 = H₄PDPA）and 1,3-di（3’,5’-dicarboxylphenyl）benzene（L4 = H₄DPB）,and matal,Cd,Co,In and Li,allowed for the solvothermal synthesis of eight new porous MOFs:{Cd₂（L1）（CH₃CH₂O）（DMA）（H₂O）}_n（1）{Co₂（L1）（DMA）（H₂O）₂?（DMA）₂}_n（2）{In（L1）?（DMP）}_n（3）{In（L1）?（DMF）}_n（4）{[Li_5.5（L1）₄（DMF）（H₂O）?（H₂O）]}_n（5）{[Li₃（L2）（DMF）（H₂O）?（H₂O）]}_n（6）{[Li₄（L3）（DMF）₂]}_n（7）{[Li₅（L4）₂（H₂O）?（H₂O）]}_n（8）The physical and chemical properties of all the compounds have been studied by single X-ray crystallography,Powder X-ray crystallography,Infrared spectroscopy,Thermal gravimetric analysis,Fluorescence spectrum,Semiconductor performance,Capacitor performance and so on.The main contents include two parts as follows:（1）Based on 3,3’,5,5’-biphenyl tetracarboxylate for compounds 1-5,isomorphic compounds 1 and 2,binuclear clusters M₂（COO）₃(M = Cd²⁺,Co²⁺),the binuclear clusters and ligands which extend into the two-dimensional layer in the ac plane,have formed a three-dimensional structure with two different types of pores in the direction of b-axis direction.For isomers 3 and 4,differing angles resulted within the two ligand benzene rings which are 61.9 ° and 16.0° respectively,were self-assembled under the different solvents.The compound 5,a tetranuclear cluster（LiO₄）₄ which formed by connecting the sides of the LiO₄ tetrahedra,and which has a wave-like one-dimensional chain {（LiO₄）₄}_n forms two types of sandwich-like two-dimensional layers,which then form a three-dimensional structure.The capacitive properties of the above five compounds were studied.When the current density is 1A g^-1,the capacitance of the compound 1-5 are 35.9 F g^-1、111.9 F g^-1,25.0 F g^-1,34.7 F g^-1and 49.6F g^-1.（2）Based on the flexible ligands L2,L3 and L4 regarding the respective compound 6-8.The compound 6,trinuclear-lithium cluster Li₃（COO）₃,has one-dimensional columnar chains which formed the three-dimensional channel using a ligand at an angle of 79.2° which in turn produced a（6,6）-connected topology network structure.The compound 7,tetranuclear lithium clusters Li₄（μ₂-O）₂（COO）₄,has three-dimensional channel which were formed by sharing both the one-dimensional chain and two carboxyl groups.The compound 8,mononuclear lithium clusters（Li（1）O₄）,binuclear clusters（Li₂（COO）₄）and butterfly-type hexanuclear Li₆（COO）₆,possess a scissor-like two-dimensional plane that intersects through a shared hexanuclear lithium clusters.Then,the two-dimensional layers are connected by hexanuclear clusters to form a three-dimensional diamond-shaped channel structure.When the current density is 1 A g^-1,the capacitance of the compounds 6-8 are 34.1 F g^-1、35.0 F g^-1 and 17.9 F g^-1.