Construction And Gas Adsorption Study Of Metal-Organic Frameworks Based On Azole/Azolecarboxylate Ligands

The main energy source of human production activities comes from the burning of fossil fuels.However,the resulting large amounts of untreated carbon dioxide emissions into the atmosphere will cause global warming and pose a serious threat to the healthy development of the ecological environment.Thus,the selective adsorption and separation of CO₂ has been becoming a promising approach to encounter this rapid global environmental problem.Among various adsorbents,MOFs with particular structural characteristicshave showed unique advantages for CO₂ capture:?1?open metal sites or Lewis base sites;?2?structural characteristics of ultramicro-pore;?3?interpenetrating structure and so on.Therefore,the design and synthesis of MOFs with the above characteristics are of great value for controlling greenhouse gas emissions.On the other hand,organic ligand plays an important role in MOFs design.According to Hard-Soft-Acid-Base,MOFs formed by the coordination of azolic nitrogen with Co²⁺,Ni²⁺,Cu²⁺reveal relatively higher stability,and the uncoordinated Lewis base sites can promote the CO₂ adsorption behavior.Therefore,in this paper,we mainly focuse on the synthesis of MOFs with azole and azolecarboxylate Ligands and study of their CO₂ adsorption and separation.In this thesis,five novel MOFs have been successfully synthesized under solvothermal conditions.Crystallographic analysis indicates that Compound 1 and compound 2 with different metal ions are isoreticular and both constructed by binuclear[M₂??₂-Cl??COO?₂N₄]?M=Co,Ni?and a 3-connected hetero-N,O donor ligand.The overall framework possesses a?3,6?-connected dag topology.Furthermore,both of them feature ultramicroporous channels of 3.5?×3.4?,which is suitable to adsorb the smaller carbon dioxide but not the larger nitrogen gas.Therefore,They exhibit good performance for CO₂/N₂ separation,which are promising materials for gas adsorption and purificaiton.Compound 3 is a three-dimensional copper-based organic framework formed by BTBA and Cu?NO₃?₂·3H₂O.There are two kinds ofone-dimensional channels in its structure,which are 5?×12?and 10?×10?,respectively.Compound 4 is also a three-dimensional Cu-based organic frameworks formed by TBTB and Cu?NO₃?₂·3H₂O,which reveals two kinds of pores,one is 11?×5?along the X-axis and Y-axis,and the other along the Z-axis is 9?×6?.The behaviour of the high adsorption enthalpy indicates the strong interactions between the CO₂ and the framework of MOFs,which can be ascribed to the uncoordinated N-heteroatom sites.Compound 5 is a two-dimensional framework formed by TBIB and CuCl₂·2H₂O.