| Nov 06, 2024 |
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(Nanowerk News) Metal-Organic Frameworks (MOFs) are porous crystalline materials whose structure resembles a scaffold of beams around a large empty space; this internal space can be used to store gases like hydrogen and methane or to absorb impurities.
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The research team led by Mauro Gemmi at the Center for Materials Interfaces of Istituto Italiano di Tecnologia (IIT-Italian Institute of Technology) in Pontedera (Pisa) recently developed a new environmentally sustainable MOF, both in terms of the green chemistry techniques used and the material itself: one of its components, protocatechuic acid, is a compound naturally found in various edible plants, including onions, brown rice, and gooseberries.
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The research was published in the journal Crystal Growth and Design (“Mechanochemical Synthesis and Three-Dimensional Electron Diffraction Structure Solution of a Novel Cu-Based Protocatechuate Metal–Organic Framework”) and originated as part of the NanED project funded by the European Union.
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MOFs are materials made by organic molecules that connect metal centers. The IIT team created and determined the atomic arrangement of a new MOF by linking copper atoms with protocatechuic acid bridges, a compound naturally occurring and therefore easily obtainable. This makes the new material more economically and environmentally sustainable.
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Additionally, the MOF was synthesized through mechanochemistry, a procedure that combines reagents in a shaker mill without adding any harsh solvents. The effect of this green technique is the production of very small crystals (i.e., less than 1 micron in size), which are usually difficult to study to determine their crystal structure, a critical step for understanding their chemical and physical properties
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Our expertise in electron crystallography was essential for studying the new materials,” comments Mauro Gemmi. “Through 3D electron diffraction, which uses a transmission electron microscope, we were able to analyze how a tiny electron beam is scattered by these nanoscale, invisible crystals, thus determining the arrangement of atoms in the various three-dimensional structures”
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The study has been carried out within the European NanED project, which aims at developing 3D electron diffraction technique applications in different fields. This technique is particularly useful to get the crystal structure (i.e. the atomic arrangement) of nanocrystals, since to date it is the only method that can provide these data.
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However, 3D electron diffraction is so recent that it is still under development, requiring the education of new experts in the field. The NanED project sees 14 PhD students trained in the development and application of 3D electron diffraction to several different fields, from solid state chemistry to organic chemistry, from protein crystallography to nanoelectronics.
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The project has already achieved important outcomes, such as the crystal structure determination of nanocrystalline pharmaceuticals, the application of artificial intelligence tools to the structure determination of macromolecules, such as proteins, and the characterization of the crystal structure of thin films, which could find important applications in nanoelectronics.
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“We used natural ingredients to synthesize in a fully sustainable way a new MOF – explains Gemmi – that could be used, among others, also as pollutant absorber. This, coupled to innovative and powerful characterization methods, which allows us to study the crystalline matter at a level of definition never achieved before, could pave the way for a so called green chemistry”.
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