Recent advances in the shaping of metal–organic frameworks
The shaping of metal–organic frameworks (MOFs), referring to the integration of small submillimeter MOF crystals into bulk samples with desired size, shape and mechanical stability, is an important step for the practical use of this class of porous materials in many applications. MOFs are constructed by the coordination bonding of metal ions/clusters and organic ligands. Since coordination bonds are mostly weaker than covalent bands, MOFs show a relatively low stability compared to conventional porous materials, such as zeolites or porous carbon-based materials. Thus, many shaping methods for the conventional porous materials involving treatments under harsh conditions could not be directly applied to prepare shaped MOFs. However, the inorganic–organic hybrid nature of MOFs also affords the opportunity of developing unique methods for shaping the materials. Herein, an overview of some classic methods for the shaping of MOFs is presented, including granulation, extrusion, spray drying, and pressing. In addition, the recently developed methods for the preparation of shaped MOFs used in separation and gas storage, including templated shaping, self-shaping, shaping by in situ growth on substrates, and shaping with sacrificial materials, are highlighted.