| Metal-organic frameworks(MOFs), also known as coordination polymers, wereregarded to have first been developed around20years before. They have infinitecrystalline lattices which generally involve two main components of inorganicvertices (metal ions or clusters) and organic linkers/struts. The two main componentsare connected to each other by coordination bonds, together with other intermolecularinteractions, to afford a network having definite topology with pores usually occupiedby solvent molecules.Emerging as a new class of porous materials, MOFs have attracted tremendousattention in recent years, as can be seen from the rapidly increasing publicationsdevoted to this field. In contrast to the preferred new structure explorations andinvestigations in early stage, the development of multifunctional applications ofMOFs have attracted more scientific interest in recent decades. Due to the closecorrelation between MOF structures and their potential properties, the‘‘real design’’of desirable structures with expected properties becomes very important and attractivealthough it is still a very challenging issue. Generally speaking, most of the functionalproperties of MOFs are dominated by their pores. Therefore, to construct MOFs withsuitable pore sizes, shapes and environments is of great interest and importance fortheir functional applications.Porous MOFs generally have microporous (<2nm) characters whereas the poresizes could be tuned from several angstroms to several nanometers by typicallycontrolling the length of the rigid organic ligands or by controlling theinterpenetration. Moreover, the pore walls and environments can be modified/functionalized by specific ligand design or postsynthetic modification. The extensivemodulations of pore sizes and framework structures of MOFs endow them anincredibly high surface area, These unique characteristics of MOFs set them apartfrom other traditional porous materials. Zeolites and mesoporous silica are usuallycrystalline but fully inorganic and thus lack synthetic flexibility and structuraldiversity/tailorability, and porous carbon materials and aerogels are almost amorphous or partially ordered. Porous MOFs were found to have extremely plentiful structuresand topologies, and have been developed as multifunctional materials to displayversatile excellent physical properties, such as, magnetism, fluorescence, catalysis,gas storage and separation, hosting guest molecules or nanoparticles (NPs) or asnanoreactors, thin films, sensing or recognition, proton conduction, drug delivery,and so on. Considering the available reviews on MOFs, in this feature article, wefocus on the recent developments concerning the following four newly emergingfunctional applications: sorption and separation, heterogeneous catalysis (mainly,gas-phase), as supports/host matrices for small metal NPs, and as templates/nanoreactors for new material syntheses. Additionally, one of the main weaknesses ofMOF materials maybe ascribed to their rather low thermal, hydrothermal, andchemical stabilities when compared with zeolites, a fact that may undoubtedly limittheir use in large scale in dustrial applications. However, we recently presented a firstgeneration of a zirconium-based MOF(UiO-66) characterized by very high surfacearea and with an unprecedented thermal stability. In this respect, the recentlysynthesized MOF UiO-66(Zr) has attracted particular interest. UiO-66(Zr) exhibits ahigh surface area, a very good thermal stability, and interestingly an outstandingchemical stability (against water, acetone, dimethylformamide, and benzene).We successfully synthesized UIO-66and UIO-66-NO2of metal–organicframeworks (MOFs) in this critical review and tried to prepare two MOFs membranesystem of the two membrane-forming properties of MOFs. Studies have shown thatUIO-66-NO2shows a relatively good membrane-forming properties, but also to befurther studied. UIO-66and polyethersulfone (PES) the composite preparationUIO-66/PES mixed-matrix membranes(MMMs), and studied the morphology of themixed-matrix membranes. |
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