Coordination Polymers Based On Chiral Polyfunctional Ligands Synthesis, Characterization And Performance Study

Crystalline porous coordination polymers or metal-organic frameworks (MOFs) with periodic network structures are auto-assembled by the coordination of multidentate ligand molecules to metal centers. Compared with traditional porous materials, MOFs are synthesized under mild conditions and thus allow rational design of novel materials by incorporating bridging ligands with desired size, shape and electronic properties. Moreover, chirality can be imparted on MOFs using chiral ligands as the linkers of the networks. Chiral MOFs combine both chirality and porosity properties. It is challenging to design and synthesize such crystalline materials combining both properties so far.In this thesis, we designed and synthesized three octahydrobinaphthalene-derived multifunctional chiral ligands (showed as H₂Lx₁ - HLx₃). We used hydrothermal and solvothermal synthesis to obtain six chiral metal-organic frameworks (showed as FDCX-n) by the reactions with one of chiral ligands, (R)-2,2'-dimethoxy-5,5',6,6',7,7',8,8'-octahydro-1,1'-binaphthyl-3,3'-dicarboxylic acid (H₂Lx₁), and transition metal salts, showed as: [Cu(Lx₁)(Py)₃](FDCX-1), [Cd(Lx₁)(Py)₃](FDCX-2), [Zn(Lx₁)(Py)₂](FDCX-3), {Na[Cd(Lx₁)(HLx₁)]·2.5H₂O} (FDCX-4), {[NH₂(CH₃)₂][Cd(Lx₁')₂]·DMF·H₂O}(FDCX-5) and [Zn₄(Lx₁)₄] (FDCX-6); used diffusional synthesis to get a chiral MOFs: {[NH₂(CH₃)₂]₂ [Cd₃O(Lx₁)₃(H₂O)₃]₂·6H₂O}(FDCX-7). X-ray single-crystal diffraction, elemental analysis, infrared spectroscopy (IR) and thermogravimetric analysis (TGA) were performed. The crystalline phase purity of each sample was independently confirmed by powder X-ray diffraction.X-ray single-crystal diffraction studies reveal that FDCX-1 and FDCX-2 both adopt one-dimensioanl (1D) infinite helical structures, while FDCX-3 possesses 1D linear chain network. FDCX-4 holds 2D layer structure which is composed of Cd²⁺ ions as nodes and chiral ligands Lx₁^2- and HLx₁ as linkers, dopting ABAB offset stacking modes. In the structure of FDCX-6, the chiral ligands Lx₁^2- joint the five-connect binuclear secondary building units(SBU) "Zn₂(RCO₂)₃(RCO₂)₂" to form 1D chain structures by a three-connect coordination mode, and then other ligands Lx₁^2- join the 1D chains to form 2D layer networks by a two-connect coordination modes. FDCX-7 adopts 2D layer network with hexagonal pore made of rare six-connect trinuclear secondary building units(SBU) "Cd₃O(RCO₂)₃(RCO₂)₃(H₂O)₃" as vertexs and chiral ligands Lx₁^2-as nodes.The two methoxy groups of chiral ligand H₂Lx₁ were hydrolyzed in situ to form another ligand Lx₁'^2- in the structure of FDCX-5. The chiral ligands Lx₁'^2- link the four-connect eight-coordinate dodecahedron Cd²⁺ ions to form a two-dimensional (2D) layer structure along a axis and c axis. FDCX-5 adopts ABCDABCD offset stacking mode.Thermogravimetric analyses (TGA) display that FDCX-4 is thermally stable to 330℃and FDCX-6 is thermally stable to 350℃, which are rare for homochiral MOFs. The solid fluorescence emission spectra of FDCX-2 - 4 show purple photofluorescence at room temperature. FDCX-1 could adsorption racemic 2-butanol when actived by heating in the vacuum.