An international group of scientists from the Novosibirsk State University laboratory on the structure and functional properties of molecular systems at the SB RAS Institute of Catalysis, the SB RAS Institute of Inorganic Chemistry, and the University of Manchester have developed a new kind of microporous materials - metal-organic scaffolds, based on the principles of directed molecular design.
Metal-organic frameworks represent a new class of porous hybrid materials with a regular crystal structure consisting of inorganic centers connected by organic bridging ligands. This organization creates conditions for the creation of porous materials with extremely diverse chemical compositions and is a platform for the directed synthesis of functional materials for a wide range of applications.
In a work published in the prestigious international journal, Proceedings of the National Academy of Sciences, scientists describe how they managed to obtain a series of stable porous frameworks combining an extra high specific pore surface (~ 3000-4000 m2 / g) and directional synthesis high working capacity of methane retention (0.24 g / g, 163 cm3 / cm-3 at 298 K, 5-65 bar).
Thus, when using these materials as a filler, it is possible to increase several times the capacity of standard gas cylinders (for example, used in cars with gas engines) while maintaining safe working pressures.
“Our important achievement is the controlled size and geometry of the pores: while maintaining the overall topology of the framework, the length of the cylindrical pores is regulated by a directed change in the central part of the organic linker”, says Danil Kolokolov, associate professor at the NSU laboratory of the structure and functional properties of molecular systems.
Another distinguishing feature of these materials is the presence of highly mobile structural fragments in porous frameworks. Thus, the framework is a regular structure of the stochastic molecular rotors. In this case, the nature of this structural mobility can have a significant effect on other functional properties, for example, on the frequency dependence of the permittivity or the ability to adsorb substances of different chemical nature.
Novosibirsk scientists made the primary contribution to the study of structural mobility of new materials and made it possible to demonstrate that the design of an organic linker allows it to regulate the speed and other parameters of rotation of mobile molecular structural fragments.
According to Kolokolov, on the one hand this result has fundamental importance because with the help of molecular design it was possible to achieve detailed control over the properties of porous frameworks. On the other hand, there are practical applications, it was possible to create a series of materials with adjustable permittivity parameters, which can be used in the creation of new dielectrics, and also as materials for chemical sensors.
