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[求助]
求助1段英語翻譯成中文
Metal-organic frameworks (MOFs) are a class of crystalline hybrid materials whose crystal structure is made up of extended 3D networks of metal ions or small discrete clusters connected through multidentate organic spacers. To become a MOF, these building units organize spatially in such a way that crystalline porous structures defining channels and cavities of regular size and shape on the nanometer scale are formed. The crystal framework of MOFs is analogous to that of zeolites and other related purely inorganic porous materials, but there are clear differences between them concerning porosity, range of stability, and feasibility of building a crystal structure by design. In particular, MOFs exhibit values of specific surface areas of up to 3000 m2 g-1 and specific pore volumes of up to 1 g cm-3,
which are among the highest values ever reported for any material. MOFs have an extremely wide-open structure in which the free space available for host molecules can reach up to 90% of the crystal volume. This results in the lowest densities
attained so far for any crystalline material (a value as small as 0.21 g cm-3 has been reported for IRMOF-16). Also in the case of MOFs it is possible to achieve a fine control over the chemical environment and the topology of the internal voids
by selecting appropriate building blocks (dimensions and functionalities of the organic linkers and size of the metal clusters) and the way in which they are connected. However, due to the presence of organic building blocks, MOFs are
obviously much less stable than zeolites to thermal treatments, to moisture, and to chemical agents. |
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