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1 2021

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Struktura i właściwości fizykochemiczne polimerów koordynacyjnych oraz materiałów typu MOF kadmu(II) i cynku(II)

Pobłocki Kacper, Drzeżdżon Joanna, Jacewicz Dagmara

Wiadomości Chemiczne

2021

[Z] 75, 7-8

1041--1073

In 1964, J.C. Bailat Jr. was one of the first scientists who use coordination polymers in his research. He established the rules of structure and the composition of compounds containing metal ions and organic ligands connected by coordination bonds to form layered or chain structures. He compared inorganic compounds belonging to polymeric species with organic polymers. The term Metal Organic Frameworks (MOF) was first used in the publication by О. M. Yaghia. Crystalline, microporous structures contain rigid organic ligands (used interchangeably: organic building blocks) that bind metal ions. This is called reticular synthesis. MOF surface area values usually range from 1000 to 10000 m2/g-1, thus exceeding the area values of traditional porous materials such as zeolites and carbons. Metal Organic Frameworks create porous three-dimensional structures, unlike coordination polymers. Inorganic minerals from the aluminosilicate group are used in the widespread heterogeneous catalysis and processes such as: adsorption and ion exchange, while compared to Metal Organic Frameworks, shows a lower potential than zeolites, moreover, the design of structures is less precise and rational due to the lack of shape, size and control functionalization of pores. To date, MOF are the most diverse and most numerous class of porous materials. All aspects have made them ideal structures for storing fuels such as hydrogen and methane. They are perfect for catalytic reactions and are good materials for capturing pollutants, e.g. CO2. The number of publications on coordination polymers (CP), Metal Organic Frameworks (MOF) or a group of hybrid compounds (organic-inorganic) increased tenfold at the turn of 2005, which proves the growing interest in this field by scientists around the world. MOF diversity in terms of structure, size, geometry, functionality and flexibility of MOF has led to the study of over 20,000 different MOF’s over the past decade. The search for new materials consists of combining molecular building blocks with the desired physicochemical properties. To produce a solid, porous material that can be used in the construction of a "molecular scaffold", rigid organic moieties, which are described in the literature as rods, must be combined with multi-core, inelastic inorganic clusters that act as joints (also called SBU secondary building units). By design, multi-core cluster nodes are able to impart thermodynamic stability through strong covalent bonds and mechanical stability due to coordination bonds that can stabilize the position of metals in the molecule. This property contrasts with those of the unstable single coordination polymers. The size and most importantly the chemical environment of the resulting voids are determined by the length and functions of the organic unit. Therefore, adjusting the appropriate properties of the material is made by appropriate selection of the starting materials. The isoretical method made it possible to use MOF structures with large pores (98 Á and low densities (0.13 g/cm3). This method involves changing the size and nature of Metal Organic Frameworks without changing the topology of their substrate. Thanks to this, it was possible to include large molecules such as vitamins (e.g. B12) or proteins (e.g. green fluorescence protein) into their structure and use the pores as reaction vessels. The thermal and chemical stability of many MOFs has made them amenable to functionalization by post-synthetic covalent organic complexes with metals. These properties make it possible to significantly improve gas storage in MOF structures and have led to their extensive research into the catalysis of organic reactions, activation of small molecules such as hydrogen, methane and water, gas separation, biomedical imaging and conductivity. Currently, methods of producing nanocrystals and MOF super crystals for their incorporation into specialized devices are being developed. Crystalline structures of MOF’s are formed by creating strong bonds between inorganic and organic units. Careful selection of MOF components produces crystals of giant porosity, high thermal and chemical stability. These features allow the interior of the MOF to be chemically altered to separate and store gases. The uniqueness of MOF materials is that they are the only solids to modify and increase the particle size without changing the substrate topology.