Newly Emerging Metal–Organic Frameworks (MOF), MXenes and Zeolite …
221
2 Metal–Organic Framework, Zeolite and MXene
Nanosheets
2.1 MOF Nanosheets
High surface areas and well-ordered porous structures make crystalline porous materials (CPM) that show great potential in separation and adsorption [24]. Among them,
MOFs, which are typically constructed from metal ions/clusters and organic ligands
via coordination bonds, have attracted much attention [25, 26]. Both the metal ions
chemistry and ligand preparation versatility endow MOFs with great tunability and
distinguished interesting properties, such as chemical functionality, porosity, and
stability, compared with other porous materials. Thus, MOFs have been of particular interest and have been used in multidisciplinary areas since its first discovery in
1995 [27]. Thanks to their facile synthesis, large surface area, and chemical stability;
MOFs show great potential applications in purification and separation [28].
Tailorable pore structure and sizes, and porous structures with numerous active
sites make MOFs very promising in treating contaminants through adsorption [10].
Compared with other adsorbents, such as zeolites whose pores are limited by small
size formed through inorganic crosslinking anions, MOFs display advances owing
to their variable choices of metal ions and building blocks. The pore sizes of MOFs
could be tuned in the range of few angstroms to several nanometers.
Layered MOFs constitute 2D layers assembled in a vertical direction by stacking
via weak interactions, such as Van der Waals forces, hydrogen bonding, and π-π
stacking. These weak interactions can be easily disrupted. As a result, the stacked
MOFs would be exfoliated to 2D MOF nanosheets. For 2D MOF nanosheets, more
accessible active sites are exposed on surface, facilitating the interactions between
active sites and substrate molecules and improving the separation performance.
2.2 Zeolite Nanosheets
Zeolite, typically in forms of NaA, MFI, FAU, etc., is a kind of aluminosilicate
minerals with a microstructures composed of three-dimensionally (3D) connected
nanopores of 0.3–0.8 nm [29]. Considerable attention has been paid to layered
zeolites with a thickness varying from one to several unit cells [30]. Moreover,
232 distinct zeolite topologies have been identified and included in the International
Zeolite Associations (IZA) database to date, while 48 millions or more have been
theoretically predicted [31].
221
2 Metal–Organic Framework, Zeolite and MXene
Nanosheets
2.1 MOF Nanosheets
High surface areas and well-ordered porous structures make crystalline porous materials (CPM) that show great potential in separation and adsorption [24]. Among them,
MOFs, which are typically constructed from metal ions/clusters and organic ligands
via coordination bonds, have attracted much attention [25, 26]. Both the metal ions
chemistry and ligand preparation versatility endow MOFs with great tunability and
distinguished interesting properties, such as chemical functionality, porosity, and
stability, compared with other porous materials. Thus, MOFs have been of particular interest and have been used in multidisciplinary areas since its first discovery in
1995 [27]. Thanks to their facile synthesis, large surface area, and chemical stability;
MOFs show great potential applications in purification and separation [28].
Tailorable pore structure and sizes, and porous structures with numerous active
sites make MOFs very promising in treating contaminants through adsorption [10].
Compared with other adsorbents, such as zeolites whose pores are limited by small
size formed through inorganic crosslinking anions, MOFs display advances owing
to their variable choices of metal ions and building blocks. The pore sizes of MOFs
could be tuned in the range of few angstroms to several nanometers.
Layered MOFs constitute 2D layers assembled in a vertical direction by stacking
via weak interactions, such as Van der Waals forces, hydrogen bonding, and π-π
stacking. These weak interactions can be easily disrupted. As a result, the stacked
MOFs would be exfoliated to 2D MOF nanosheets. For 2D MOF nanosheets, more
accessible active sites are exposed on surface, facilitating the interactions between
active sites and substrate molecules and improving the separation performance.
2.2 Zeolite Nanosheets
Zeolite, typically in forms of NaA, MFI, FAU, etc., is a kind of aluminosilicate
minerals with a microstructures composed of three-dimensionally (3D) connected
nanopores of 0.3–0.8 nm [29]. Considerable attention has been paid to layered
zeolites with a thickness varying from one to several unit cells [30]. Moreover,
232 distinct zeolite topologies have been identified and included in the International
Zeolite Associations (IZA) database to date, while 48 millions or more have been
theoretically predicted [31].