Construction And Properties Of Microporous Coordination Complexes Based On Carboxylate-Containing Ligands

During the last decade, metal-organic framework (MOFs) or porous coordination polymers (PCPs) rapidly emerging as a new class of porous material have attracted considerable attention not only because of their intriguing varieties of architectures and topologies, but also due to their potential applications in sorption, magnetism, catalysis, non-linear optics, and so on. Most of studies in this field have been focused on design and construction of MOFs, and attempt to open out their structure-property relationship. Although a great progress has been achieved, it is still a challenge to rational design and synthesis MOFs with definite structure and property. Undoubtedly, from the viewpoint of crystal engineering, the most effective and facile approach is the appropriate choice of well-designed organic ligands together with metal centers with specific coordination preferences.In the dissertation, four compounds with carboxylate groups namely, N-(4-pyridylmethyl)iminodiacetic acid (H2PMIDA), [1,1’:3’,1"-terphenyl]-4,4",5’-tricarboxylic acid (H3TPTC),5-(pyridin-4-yl)isophthalic acid (H2PYIP),3,5-di(pyridine-4-yl)benzoic acid (HDPB) are used to reaction with metal salts, and obtained nine new complexes. All the complexes are characterized by single crystal X-ray diffraction, elemental analyses, IR, powder X-ray diffraction (PXRD) and thermogravimetric analyses. Sorption properties of some complexes are studied in detail. There are four main parts in the dissertation:1. The reactions of H2PMIDA with Cd(Ⅱ)/Zn(Ⅱ) salts gave three novel MOFs namely {[Cd(PMIDA)(H2O)]·1.8H2O}n (1),{[Cd(PMIDA)(H2O)]·2H2O}n (2) and {[Zn(PMIDA)(H2O)]·2H2O}n (3). Complex 1 has a unique irl topologic 3D framework constructed from rod-shaped Cd(Ⅱ) carboxylate secondary building units (SBUs), whereas complexes 2 and 3 are isostructural and possess dia topology based on tetra-nuclear square Cd(Ⅱ)/Zn(Ⅱ) carboxylate SBUs. Interestingly, complexes 1 and 2 obtained by the same reaction are supramolecular isomers with different 3D structures and topologies. Second-order non-linear optical (NLO) effect of the complexes, ferroelectric property of 1 as well as sorption properties of 1 and 3 were investigated. The flexible frameworks endow complexes 1 and 3 with stepwise behavior and large hysteresis for H2O adsorption and selective sorption properties for H2O and MeOH over N2 and EtOH.2. A new micro-porous MOF{[Cu3(TPTC)2(DABCO)(H2O)]·15H2O·9DMF}n (4) (DABCO= 1,4-diazabicyclo[2.2.2]octane) has been synthesized by the reaction of H3TPTC and DABCO with copper(II) nitrate trihydrate under solvothermal conditions, which showed good stability up to 533 K after the removal of lattice solvent molecules. Complex 4 is a 3D non-interpenetrated porous framework. Interestingly, complex 4 showed very good adsorption capacity for H2 (54.3 mg g-1 at 77 K and 20 bar), CO2 (871 mg g-1 at 298 K and 20 bar), CH4 (116.7 mg g-1,99 cm3(STP) cm-3 at 298 K and 20 bar) and n-pentane (686 mg g-1 at 298 K and 1 bar), respectively. In addition, complex 4 exhibits excellent selectivity toward CO2 over N2 at ambient temperature.3. Three porous MOFs, namely,{[Co(L)(PIN)]·dioxane·H2O}n (5),{[Co(L)(DPE)]·0.5DPE}n (6) and{[Co(L)(BPE)]·4H20}n (7) with the same 2-fold interpenetrating hms topology were constructed by reactions of H2PYIP and different pillar ligands of N-(4-pyridyl)isonicotinamide) (PIN), 1,2-di(4-pyridyl)ethylene) (DPE) and 1,2-bis(4-pyridyl)ethane (BPE). Interestingly,5 possesses a flexible framework upon desolvation and H2O/MeOH/EtOH vapor adsorption, and the desolvated sample exhibits a stepwise uptake of CO2(195 K), H2O (298 K) and MeOH (298 K). More importantly, the desolvated 5 shows high enthalpy of CO2 adsorption and high selectivity for CO2 over N2 at 298 K. In addition, second-order non-linear optical (NLO) effect and ferroelectric property of 7 were investigated.4. Two novel isostructural microporous MOFs, namely,{[Ni(DPB)2]·4H2O}n (8) and {[Co(DPB)2]·4H2O}n (9), with uncoordinated pyridine decorated pores were synthesized by the reactions of HDPB with Co(Ⅱ)/Ni(Ⅱ) salts under hydrothermal conditions. Remarkably,8 and 9 possess flexible frameworks with high stability and excellent sorption selectivity and higher adsorption enthalpy for CO2. In addition, H2O, MeOH and EtOH vapor sorption isotherms are investigated.