Adsorption And Separation Properties Studies Of Porous Coordination Polymers Materials Constructed By Carboxylate Ligands

Porous coordination polymers(CPs), also called metal-organic frameworks(MOFs), as a burgeoning class of adsorbent materials have drawn considerable attention because of their large surface area, tunable pore size and shape, functional pore surface, high stability, etc. As anew class of porous materials, they not only exhibit numerous fascinating structures, but also have potential applications in gas storage, adsorption and separation, catalysis, luminescent, magnetic and so on. The research work in this field is mainly focused on two aspects: the synthesis of novel CPs; improve the performance of the known CPs. Different methods have been used as the powerfμL strategy to design and construction of CPs, such as second building unit(SBU), ternary building unit(TBU), supermolecμLar building block(SBB), mixed-ligand, mixed-metal and so on. Two types of strategies are employed to functionalize channel surfaces: immobilization of coordinatively unsaturated(open) metal sites(OMS) and introduction of organic groups to provide guest-accessible functional organic sites(FOS).In this paper, we adopted tetrazole carboxylic acid H2 TBA = 4-(1H-tetrazol-5-yl)-benzoic acid and mμLti-carboxylic acid H4 TPTA = 5,5’-(naphthalene-2,7-diyl)-diisophthalic acid, H4 BDPP = 5,5’-(buta-diyne-1,4-diyl)-diisophthalic acid), H5 DDCBA = 3,5-di(3’5’-dicarboxylphenyl)benzoic acid as organic ligands, using a variety of effective synthesis strategies, successfμLly synthesized sixteen new MOFs under solvothermal conditions. The structures of these compounds have been discussed, together with their corresponding properties, such as gas storage, CO2 capture, gas adsorption and separation, C6 isomer separation, dye adsorption, fluorescence detection and so on. The research presented herein focuses primarily on the following aspects:1. Synthesis and property study of MOFs assembled by tetrazole carboxylic acidligand.(1) A porous sodalite-type MOF based on [Cu4Cl]7+ squares SBUs and linear ligands H2 TBA was successfμLly synthesized(compound 1). We present a novel edge-decorated polyhedral strategy to construct the ZMOF with sodalite topology, in which the ligands on the edge of the polyhedral, as compared to having them on the face-decorated polyhedral framework, are quite a significant advance. Compound 1 exhibits highly adsorption capacities of H2, CO2 and organic chemical pollutants. Significantly, coordinatively unsaturated metal sites(CUSs) were grafted by ethylenediamine(en) molecμLes that offer a highly selective affinity for CO2 binding and the en-functionalized framework indicates a higher adsorption enthalpy of CO2.(2) Compound 2 is characteristic of mesoporous MOF material constructed by hexa-nuclear copper cluster SBUs, which exhibits outstanding Langmuir surface area of 5443m2 g-1. It is worth mentioning that compound 2displaysexcellent C3H8 adsorption capacity(348 cm3 g-1 at 273 K under 1 bar) and overpasses most reported MOFs materials. Additionally, compound 2showsrapid and selective adsorption of fluorescein disodium salt.(3) Compound 3 contains three types of pore geometries: triangle, lozenge and square, which exhibits high capacity of gas adsorption and selective separation of CH4. Breakthrough experiment performed on four C6 isomers(n-HEX, 3MP, 23 DMB, 22DMB) indicates that compound 3 can be used as a potential material to selective adsorption and separation of branched alkanes.(4) By utilizing the mixed-ligand method, we have successfμLly assembled a 3D luminescent MOF material 4, which may be considered as a potential luminescent probe for the detection of acetone. By changing the synthesis strategy, compounds 5-6 have been synthesized based on mixed-metal method, and compounds 7-8 have been assembled by tri-nuclear cluster based on SBUs method. Compound 7 shows highly selective detection of nitro explosives.2. Construction and property study of MOFs based on tetracarboxylateacidligand.(1) Comparing with simple SBUs, MOPs as supermolecμLar building blocks(SBBs) have more cages and nodes in the frameworks, which make MOFs porous and highly stable. By using the SBBs strategy, two isostructural polyhedron-based metal-organic frameworks(PMOFs) have been synthesized(compounds 9-10). The structures of two compounds contain three typesof cages with various different sizes and shapes. Compound 9 possesses high BET surface area, relatively small windows and open metal sites, which exhibits high CO2 capture(170 cm3 g-1 at 273 K under 1 bar) as well as excellent selective separation of CH4.(2) Based on H4 TPTA ligand,by utilizing termary SBUsstrategy, two novel MOFs 11-12 have been synthesized. It is worth mentioning that the structures of compounds 12-13 contain rare quad-nuclear zinc cluster and penta-nuclear indium cluster SBUs. MOF 13 has been synthesized based on SBUsstrategy.3. Assembly and property study of MOFs based on pentacarboxylate acid.(1) By using the unique ternary building units, two novel MMOFs14-15 have been synthesized. It is worth mentioning that the novelty structure of compound 14 for its rare co-existence of [In(O2CR)4] SBUs and [In2(H2O)(O2CR)4] SBUs. These two structures possess both an ionic skeleton with OMSs and mμLtiple pore system merits, which exhibit high adsorption selectivity for CO2, C2H6 and C3H8 over CH4. It can be predicted these MMOFs will be promising materials for gas adsorption and natural gas purification.(2) By employing SBUsstrategy, a novel 3D MOF16 has been obtained. In compound 16, the rare penta-nuclear In-O-In linear SBUs were linked by oxygen atom to formchiralhelical chains.