Synthesis,Structure And Adsorption/Separation Properties Of Copper-metal Organic Frameworks Constructed By Multicarboxylate Ligands

Metal-organic frameworks,also known as porous coordination polymers,are readily assembled via metal coordination bonds from inorganic metal ions/clusters and multidentate organic bridging ligands.Therefore,they have the combined characteristics of both inorganic compounds and organic polymers.Compared with the conventional porous materials,MOFs have larger surface area and pore volume,tunable pore size and easily modifiable pore surface,making them have good application prospects in catalysis,sensing,and drug delivery,especially on gas storage and separation.In this thesis,we chose the multicarboxylate ligands and copper ion to construct MOFs materials.The organic ligands were designed and synthesized,and then were used to construct the copper-based MOFs by solvothermal method.The resulting MOFs were characterized by standard spectra technologies such as FTIR,TGA,and PXRD,and their gas adsorption properties were investigated in detail.1.We have designed and synthesized a bent diisophthalate ligand functionalized with aminopyrimidine groups,and constructed via a solvothermal reaction,a porous copper-based framework(ZJNU-54).Single-crystal X-ray diffraction studies show that the framework is a three-dimensional network containing three different types of polyhedral nanocages,which are stacked together to form two distinct types of one-dimensional channels along the crystallographic c axis.The compound after activation shows exceptionally high C2H2 and CO2 uptakes,as well as impressive adsorption selectivities towards C2H2 and CO2 over CH4.This work demonstrates that incorporating specific functional organic sites,aminopyrimidine in this case,within cage-based MOFs provides an efficient strategy for the development of functional MOF materials for highly selective gas storage and separation.2.An anionic metal-organic framework ZJNU-55 was synthesized by a solvothermal reaction of a custom-designed angular diisophthalate and CuCl2·2H2O.The structure is totally different from PCN-307 with a similar ligand.The framework exhibits a mononuclear Cu(COO)4 inorganic secondary building unit,instead of the typical dinuclear Cu2(COO)4 paddlewheel unit.As far as we are aware,this is a rare example of a MOF constructed from mononuclear Cu(COO)4 for selective gas adsorption.The activated ZJNU-55a exhibits highly selective adsorption of C2H2 and CO2 over CH4.This work demonstrates that subtle ligand modification can drastically affect the structures and properties of the resultant MOFs.3.By using a presynthetically cross-linked octacarboxylate ligand,a chemically cross-linked version of the NbO-type MOFs ZJNU-80 was prepared.ZJNU-80 adopts the same topology as the parent compound NOTT-101,and the tethering groups take part in the window partition,not the cage partition.The gas adsorption studies showed that,despite the lower porosity,ZJNU-80a exhibits low-pressure gas adsorption behavior similar to that of the parent MOF toward CO2,CH4,and N2 because of the fact that the window partition as a result of chemical cross-linking does not almost alter the pore-size distributions.However,different adsorption behaviors toward 1-butene,a molecule with even larger kinetic diameter than that of the aforementioned adsorbates,were observed because the window partition alters the efficiency with which 1-butene molecules pack within ZJNU-80a and NOTT-101a at conditions close to saturation.This work provides a fundamental understanding on the effect of chemical cross-linking on the MOF's structure and gas adsorption properties.