Syntheses,Structures And Properties Of Metal-Organic Frameworks Constructed From Carboxylic Ligands With Large Skeleton

Metal-Organic Framework?MOF?composed by metal ions or metal clusters and multidentate oxygen/nitrogen organic ligand through coordination bond is a three-dimensional?3D?network with regular channels.MOFs have some special characters such as rich structures,low density,permanent pores,ultra-high surface area and functional pore space,which are widely used in gas storage and separation,fluorescence,catalysis,sensing,and drug transportation.Rational selection of organic ligands for preparation of MOFs with novel structures and diverse properties is very important.Due to their high stability and various physical properties,MOFs constructed from the pyrene-based carboxylate and nitrogen-containing heterocyclic carboxylate ligands have been well studied.In this paper,1,3,6,8-tetrakis?4-carboxylphenyl?pyrene?H₄-TBAPy?,which is a rigid and high-symmetric ligand based on pyrene core formed by four fused benzene rings,was selected for construction of MOF.The four carboxylate groups of the H₄-TBAPy can exhibit various coordination modes.The high-nuclear cluster-based MOFs can be obtained when the H₄-TBAPy coordinated to the lanthanide ions.The 4'-?3,5-dicarboxyphenyl?-2,2',6',2''-terpyridine?H₂-DCPTP?is also a rigid and high-symmetric ligand,which provides the oxygen and nitrogen donors for bridging the metal ions.The carboxylate and terpyridine motifs can bind the metal displaying diverse coordination modes.Six MOFs based on the lanthanide ions?Eu?III?,Tb?III?,Gd?III?,Zn?II?and Cd?II??and H₄-TBAPy ligand were obtained.In addition,three MOFs constructed from H₂-DCPTP and transition metal ions such as Zn?II?and Ni?II?were isolated.?1?{?Me₂NH₂?₃[Eu₇??₃-O?₂?TBAPy?₅?H₂O?₆]·12.5DMF}_n?2?{?Me₂NH₂?₃[Tb₇??₃-O?₂?TBAPy?₅?H₂O?₆]·12.5DMF}_n?3?{?Me₂NH₂?₃[Gd₇??₃-O?₂?TBAPy?₅?H₂O?₆]·12.5DMF}_n?4?{[NaZn₅?OH?₃?TBAPy?₂?Me₂NH?₂?DMF?]·3DMF·H₂O}_n?5?{?Me₂NH₂?₂[Cd₅?TBAPy?₃?H₂O?₂]·8DMF·2H₂O}_n?6?{[Cd₂?TBAPy??H₂O?₂]·4H₂O}_n?7?[Zn?DCPTP?]_n?8?[Zn?DCPTP?·2DMF·H₂O]_n?9?[Ni_1-x-x Zn_x?DCPTP?·2DMF·H₂O]_nIn this paper,MOFs 1?8 were characterized by X-ray single crystal diffraction,X-ray powder diffraction?PXRD?,thermogravimetry and infrared spectroscopy.The gas adsorption and separation of some MOFs were tested.The fluorescence properties of two MOFs were investigated.Compound 9 was obtained by doping the zinc ions into the[Ni?DCPTP?·2DMF·H₂O]_n.This paper consists of three chapters:The first chapter introduces the research progress and synthesis methods of MOFs synthesized by metal clusters and various ligands.Then the main methods to improve the adsorption and separation performance of MOFs are introduced.The second chapter mainly describes the syntheses,structures,thermal stability,and physical properties of MOFs based on the H₄-TBAPy and H₂-DCPTP ligands.MOFs 1?3are isomorphousand formulated as{?Me₂NH₂?₃[Ln₇??₃-O?₂?TBAPy?₅?H₂O?₆]·12.5DMF}_n which are constructed from the linear trinuclear Eu₃?COO?₆ clusters and planar tetranuclear Eu₄??₃-O?₂?COO?₈ clusters.The trinuclear Eu₃?COO?₆ clusters and tetranuclear Eu₄??₃-O?₂?COO?₈ clusters are bridged by carboxylate groups to generate a 1D Eu-carboxylate rod.Each TBAPy^4–ligand bridges four 1D Eu-carboxylate rods and links the 1D rods to give a 3D framework featuring1D channels with irregular aperture.We have studied the Eu?1?in detail.The strong coordination bonds between high-charged lanthanide ions?strong acid?and carboxylate oxygen?strong base?and strong?···?stacking interactions between?-conjugated pyrenes account for the water-resistant ability of the complex Eu?1?.The PXRD and adsorption tests found that the the sample treated with water for 10 days can maintain a crystallinity and structural integrity.Furthermore,we found that the Eu?1?shows much differential adsorption amounts for C₂H₂ and CO₂,indicating its potential for C₂H₂/CO₂ separation.The C₂H₂/CO₂?50:50?selectivity are 4.8?9.2.Its separation performance was confirmed by transient breakthrough simulation and dynamic gas breakthrough experiments tests.The C₂H₂/CO₂ separation factor calculated by the experimental breakthrough curve is 9.9,which larger than most MOF materials.Finally,the gas separation mechanism of the complex was explored.The plenty of carboxylate oxygen atoms of the 1D Eu-carboxylate rods are exposed on the pore wall,which are the desirable sites for the acidic hydrogens of C₂H₂ molecules but are unfavorable sites for CO₂ molecules with two electronegative oxygen atoms.So the complex exhibits efficient C₂H₂/CO₂ separation performance.The simulation calculated results show that the preferential adsorption sites for C₂H₂ and CO₂ are locate at the channels nearby the1D Eu-carboxylate rods,C₂H₂ molecule forms strong hydrogen bonds with carboxylate oxygens.While CO₂ only forms weak interaction between the electronegative O atom and the positively charged open metal site.The metal-organic framework?4?is formed by two kinds of pentanuclear clusters[Zn₅??₃-OH?₂]connected by sodium ions and hydroxyl groups through carboxylate groups to form 1D rod-shaped structure.Each TBAPy^4?ligand bridges four 1D rods.The 1D rods are connected by TBAPy^4?ligands to generate a 3D porous structure.Compound?4?exhibits an efficient separation of propyne/propylene and propyne/propane mixtures.The separation selectivities at 298 K for propyne/propylene?50:50?mixture are 1.9?2.7 and propyne/propane?50:50?mixture are 3.8?7,respectively.The gas separation mechanism is investigated by grand canonical Monte Carlo simulation,which shows that propyne form strong C?H???O hydrogen bonds with the carboxylate oxygen atoms of the MOF.The propylene hydrogen atoms with smaller acidity form weak hydrogen bonds with the carboxylate oxygen atoms of the MOF.While the propane mainly forms C?H????weak interactions with the MOF.MOF?5?is a 3D structure based on the linear pentanuclear cadmium cluster secondary building units.Each pentanuclear cadmium cluster is surrounded by twelve TBApy^4?ligands,which link the pentanuclear cadmium clusters to give a 3D structure featuring 1D channels.From the results of the gas adsorption test,we can seen that although this compound was activated by several methods,the guest solvents cannot removed from the channels of MOF completely.Thus the suitable activation of the MOF needed to be further studied.Compound?6?is a 3D structure fromed from 1D Cd-carboxylate chains bridged by TBAPy^4?ligands.A few guest water molecules fill the voids of structure.Compound?6?features a nonporous structure and emits luminescent emission.MOF?7?and?8?was synthesized from DCPTP^2?ligands and Zn?II?ions.Each DCPTP^2?ligand bridges three Zn?II?ions in compound?7?.The DCPTP^2?ligands bridges single Zn?II?nodes to give a 3D network.Due to no any solvents in compound?7?,the large voids of the single 3D network is occupied by the same single 3D network.Thus compound?7?is a 2-fold interpenetrated 3D structure and emits luminescence.Changing the reaction conditions for compound?7?,compound?8?was isolated.compound?8?has the same 3D network with compound?7?.However,the guest solvents fill the 1D channels of framework compound?8?,which leads to a porous structure.In fact,compound?8?is isostructural to our reported compound[Ni?DCPTP?·2DMF·H₂O]_n?9a?.Compounds[Ni_1-x-x Zn_x?DCPTP?·2DMF·H₂O]_n were synthesized from dopping the Zn?II?into compound 9a.The amounts of the CO₂capture are increased after dopping.However,the enhacement of CO₂ capture is slightly.The third chapter summarizes of the thesis.