| As a new type of porous molecular-based crystalline material with outstanding structural design and control,and particularly rich properties and functions,Metal-Organic Frameworks(MOFs)has potential applications in the fields of gas adsorption,small molecule separation,catalysis,special photoelectromagnetic effects and energy conversion.Cluster-based MOF based on multinuclear metal cluster nodes is one of the most important structural categories.It has important research value in MOFs framework chemistry,crystal engineering,structure transformation and post-synthesis modification,function expansion and regulation.The MOF glasses that has emerged in recent years is the intersection of chemistry and physics,and is regarded as one of the key development directions of the next generation of porous functional materials.It also provides a rare opportunity for the study of important scientific issues related to the"glass transition"in the field of amorphous physics.There are only a few examples of MOF glasses that have been reported based on specific zeolite imidazolate-type framework such as ZIF-4 and 1D/2D-coordination polymers of imidazole phosphates,which are mainly prepared by the traditional melt-cooling method.However,the thermal stability of most MOFs is still limited,and it is often not enough to achieve melting and thermal decomposition inevitably occurs,making it difficult to prepare glass.In view of the above background and research challenges,this thesis further expands and deepens the research of the research group in the direction of"preparation of MOF glasses based on dynamic chemistry and tandem perturbation and property modulation".We used multifunctional linear pyridine carboxylate ligands and small size-oriented multidentate chelating ligands to design and synthesize four cubane-type high-nuclear cluster MOFs through mixed ligand strategy design.Reasonably utilize the coordinated substitution of water molecules and the reversible removal under thermal disturbance.The long-distance misalignment of the structure caused by the multi-step tandem disturbance enables high-nucleus cluster-based MOFs to achieve direct glass transition at medium and low temperatures.The crystalline-solid structure transition,glass transition mechanism,and the adjustment of key physicochemical properties such as brittleness coefficient,transition temperature and gas/vapor adsorption are explored.The first chapter systematically introduces the definition of metal-organic frameworks and cluster-based MOFs,the construction and application of cluster-based MOFs;analyzes the current research progress and applications of MOF glasses;briefly introduces the accumulation of this research group in MOFs and MOF glasses,as well as the significance and progress of the topic selection.The second chapter introduces that we have constructed a high cluster core containing{Co15},high symmetry,a hole rate of up to 59%,and a cationic cluster group MOF-[Co15(pybz)9(HOC2H4O)6(OC2H4O)6(NO3)3]·30Glycol(1)(pybz=4-(4-pyridinyl)benzoic acid).The study focused on the crystal structure,guest exchange,gas adsorption and magnetism of compound 1.Water was used as disturbance agent for its right coordination ability to break the dynamic equilibrium between metal nodes and organic linker,and the water is removed by heating.It shows a glass transition at Tg=570.1 K according to DSC results.Its thermal liquid fragility(mt)and kinetic liquid fragility(mk)are 75 and 87.Use TG,DSC,DMA series thermodynamic instruments to characterize and verify the formation of the glass state,combine X-ray single crystal diffraction technology,Powder diffraction,Infrared,Raman,ultraviolet,BET and Magnetometer to explore the structure information,gas adsorption and magnetism of MOF glasses.In Chapter 3,substituting cobalt chloride for cobalt nitrate to obtain compound 2-[Co15(pybz)9(HOC2H4O)6(OC2H4O)6Cl3]·28Glycol(2)with the same anion in the pores but the same framework structure;synthesis of cubane-type 15-nucleus cluster-based MOF compound3-[Co15(pybz)9(HOC3H6O)6(OC3H6O)6(NO3)3]·26Propane-1,2-diol(3)with 1,2-propanediol instead of ethylene glycol;compound 4-[Na Co8(pybz)9(HOC2H4O)6Cl2](pybz-)3(Glycol)6(4)is a highly symmetrical octa-nuclear cluster-based MOF formed by connecting two[Co4O3Cl]cubanes with Na.The glass transition was achieved through water and thermal disturbance,and the glassy MOF of the corresponding compound was successfully prepared,compound 2 Tg=565.0 K,m=71.3;compound 3 Tg=567.4 K,m=78.8;compound 4 Tg=567.2 K,m=70.4. |
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