12 Kinetic Assembly of Porous Coordination Networks …
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and unstable species has hampered progress in their basic understanding. Herein, we
demonstrated the advantages of using interactive pores to trap labile and unstable
species and observe their reactivities by X-ray analysis. The representative example
was the detection of metastable small sulfur allotropes and their interconversion for
the first time inside the pores of the helical CuI network. Interactive pores used
in these studies can be created by kinetic assembly of the coordination networks
from their precursors. Application of this method to monitoring of catalytic transformations could lead to deeper understandings of their reaction mechanisms. These
kinds of studies are crucial for the future design and development of novel functional
materials.
12.1.12 Future Perspective
Self-assembly of coordination networks has been studied intensively by many
researchers over the past quarter century. However, while the formation of kinetic
side-products has been frequently noted, their detailed investigations have been
scarce due to low stability and poor crystallinity. We demonstrated that kinetic
assembly of porous coordination networks could be used to produce materials with
interactive pore sites. The properties of these sites largely determine the possible
applications of the kinetic materials.
One promising application for the interactive pore sites is trapping and visualization of unstable species. The range of potential unstable allotropes than can be
targeted is broad and includes sulfur, phosphorus, and selenium among others. For
example, in the case of phosphorus, only it is more widely known and a more stable
form, P 4 , was encapsulated in the interactive pores. However, there are still no examples of stabilization and visualization of elusive dimer, P 2 , even though it is known
to exist at high temperatures, and has the same electronic configuration as N 2 . Therefore, this phosphorus allotrope could be a highly interesting candidate for the future
encapsulation studies.
Another intriguing application is the control of transition states. If an interactive
pore could behave like an enzyme pocket, it could be used to modulate transition
states of various transformations. Achieving such degree of control could open up new
reaction pathways that cannot be reached with the conventional methods. In addition,
interactive sites could also function as active catalytic centers, if their interactions
with a substrate lower the activation energy. Therefore, the design and construction of
the desired interactive sites from suitable metal connectors and ligands could present
and powerful approach for the development tailor-made catalysts. Some of the best
catalytic systems in existence, natural enzymes, utilize interactive sites extensively in
their functions. These systems enable unprecedented acceleration of otherwise difficult reactions, such as methane monooxygenase (MMO), which oxidizes methane
to methanol. Our ultimate goal is to develop such bio-mimetic catalysts by utilizing
interactive sites generated in kinetically assembled networks.
245
and unstable species has hampered progress in their basic understanding. Herein, we
demonstrated the advantages of using interactive pores to trap labile and unstable
species and observe their reactivities by X-ray analysis. The representative example
was the detection of metastable small sulfur allotropes and their interconversion for
the first time inside the pores of the helical CuI network. Interactive pores used
in these studies can be created by kinetic assembly of the coordination networks
from their precursors. Application of this method to monitoring of catalytic transformations could lead to deeper understandings of their reaction mechanisms. These
kinds of studies are crucial for the future design and development of novel functional
materials.
12.1.12 Future Perspective
Self-assembly of coordination networks has been studied intensively by many
researchers over the past quarter century. However, while the formation of kinetic
side-products has been frequently noted, their detailed investigations have been
scarce due to low stability and poor crystallinity. We demonstrated that kinetic
assembly of porous coordination networks could be used to produce materials with
interactive pore sites. The properties of these sites largely determine the possible
applications of the kinetic materials.
One promising application for the interactive pore sites is trapping and visualization of unstable species. The range of potential unstable allotropes than can be
targeted is broad and includes sulfur, phosphorus, and selenium among others. For
example, in the case of phosphorus, only it is more widely known and a more stable
form, P 4 , was encapsulated in the interactive pores. However, there are still no examples of stabilization and visualization of elusive dimer, P 2 , even though it is known
to exist at high temperatures, and has the same electronic configuration as N 2 . Therefore, this phosphorus allotrope could be a highly interesting candidate for the future
encapsulation studies.
Another intriguing application is the control of transition states. If an interactive
pore could behave like an enzyme pocket, it could be used to modulate transition
states of various transformations. Achieving such degree of control could open up new
reaction pathways that cannot be reached with the conventional methods. In addition,
interactive sites could also function as active catalytic centers, if their interactions
with a substrate lower the activation energy. Therefore, the design and construction of
the desired interactive sites from suitable metal connectors and ligands could present
and powerful approach for the development tailor-made catalysts. Some of the best
catalytic systems in existence, natural enzymes, utilize interactive sites extensively in
their functions. These systems enable unprecedented acceleration of otherwise difficult reactions, such as methane monooxygenase (MMO), which oxidizes methane
to methanol. Our ultimate goal is to develop such bio-mimetic catalysts by utilizing
interactive sites generated in kinetically assembled networks.