| Metal-organic frameworks(MOFs)is a kind of crystalline materials with periodic structure and infinite network formed by metal centers and organic ligands through coordination bonds.MOFs not only have elegant topological structures but also own high surface area.The diverse functional MOFs can be obtained through ligands’modification.In recent years,researchers have introduced different functional groups and metal ions into MOFs to diversify their functionalities,which have the potential applications in proton conduction,second-order nonlinear optics,catalysis,and uranyl adsorption.In this paper,the 2,2’-bipyridine-5,5’-dicarboxylic acid(H2-BPYDC),4,4’-biphenyl dicarboxylic acid(H2-BPDC),and 4,4’-dipyridylamine(DPA)were used to construction of MOFs.A series of MOFs constructed from these ligands and the metal ions such as Fe(Ⅲ),Co(II),Ni(Ⅱ),and Zn(Ⅱ)ions were synthesized.These MOFs were structurally characterized by X-ray single-crystal diffraction and IR spectra.The proton conduction,electrocatalytic performance,gas adsotpion and non-linear optical properties of some compounds were studied.Some MOFs exhibit the functional materials characters.The formula of compounds 1-11 is as following:{[Fe(H-BPYDA)(C2O4)]·(Me2NH)0.5·2H2O}n(1){[Co(H2-BPYDA)(C2O4)]·(Me2NH)0.5·2H20}n(2){[Zn(H2-BPYDA)(C2O4)]·(Me2NH)0.5·2H20}n(3){(Me2NH2)2[Zn6(μ4-O)(ad)4(BPDC)4]}n(4){[Ni(DPA)2(CrO4)(H2O)].2H20}n(5){[Co(DPA)2(CrO4)(H2O)]·2H20}n(6)[Ni(DPA)2(CrO4)]n(7)[Co(DPA)2(CrO4)]n(8)[Ni(DPA)2(WO4)]n(9)[Co(DPA)2(WO4)]n(10)[(H2-DPA)2(SiF6)]n(11)This paper is mainly divided into four chapters:The first chapter is the preface.It mainly introduces the research background,synthesis methods,classification of metal-organic frameworks,and the research on gas adsorption and separation,uranyl adsorption,proton conduction,electrocatalysis and second-order nonlinear optical effects of MOFs.It also gives a brief overview of the basis and significance of this paper.In the second chapter,three isomorphous MOFs of 1,2,and 3 were synthesized from 2,2’-bipyridine-5,5’-dicarboxylic and oxalic ligands.Based on the fact that the carboxylic group owing the proton transfer character,the 2,2’-bipyridine-5,5’-dicarboxylic and oxalic ligands were selected for construction of the MOFs.MOFs 1,2,and 3 have a one-dimensional(1D)chain structure.The 1D chains are connected by the hydrogen bonds to give the three-dimensional(3D)supramolecular framework featuring 1D channels.The water molecules in the 1D channels are hydrogen-bonded to each other to generate 1D water chains.Such a structural features will enhance the proton transfer of the MOFs.All compounds display good proton conductivity.The proton conductivity of compound 1 reaches 1.14×10-3 S cm-1 at 85℃ and 98%RH.The nuclear wastewater containing radionuclide of uranyl(UO22+)is produced in the nuclear energy power generation and uranium mining processes.Thus the uranyl separation from water is a hot topic.Compound 4 reported by our group previously was synthesized from adenine and 4,4’-biphenyl dicarboxylic ligands.Compound 4 has a 3D structure with the 1D channels wherein the uncoordinated carboxylate oxygen atoms exposed on the pores.The uncoordinated carboxylate oxygen atoms are expected to be the sorption sites for uranyl ions.Detailed experiments showed that compound 4 exhibits excellent uranyl adsorption performance and can remove the uranyl from water quickly.The maximum adsorption value is 114.7 mg·g-1 at pH=4.Thus we demonstrated an elegant example for uranyl adsorption.In Chapter 3,compounds 5-11 were synthesized with 4,4’-dipyridine amine(DPA)ligand.Compounds 5 and 6 are isomorphic structures.The pyridine nitrogen atoms of the DPA ligand can coordinate to the divalent metal ions to give robust coordination bonds.As a result,such MOFs are expected have high stability.Moreover,the stability of the MOFs are enhanced by introduced the inorganic anions including the CrO42-and WO42-into the system.Compounds 5 and 6 with the monodentate CrO42-ligand are isomorphic structures,which have a diamondoid network.The solvent molecules fill a few voids of the single diamondoid network.Thus the 4-fold interpenetrating diamondoid network is formed.Compounds 7-10 composed of Co(Ⅱ)and Ni(Ⅱ)ions are isostructural.In these compounds the metal ions are connected by the DPA and CrO42-and WO42-bridging ligands to form the 3D framework.Compounds 7-10 exhibit a catalytic oxygen production capacity in a neutral aqueous solution.Compound 8 exhibits better oxygen evolution performance in 1M KOH solution.When the current density is 10 mA cm-2,the overpotential is 398 mV and the Tafel slope is 100.12 mV dec-1.Compound 11 has 1D hydrogen-bonded helical chain based on the SiF62-and the protonated H2-DPA cations,which is crystallized in the non-centrosymmetric space group.The non-linear optical effect of compound 11 is studied in detail.The results show that compound 11 exhibits a large second-harmonic generation(SHG)effect,which is approximately 1.4 times that of KDP.Thus it is a good nonlinear optic material.The mechanism of the SHG effect was discussed briefly.Chapter 4 summarizes and prospects the work of this paper. |
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