39 research outputs found
Tailored Multifunctional Heterometallic Metal-Organic Frameworks
Metal-organic frameworks (MOFs), which are well-defined and porous extended structures consisting of organic linkers connected to inorganic secondary building units, are a class of materials that have received tremendous attention over the last decade. This geometrically growing interest in MOFs is attributed to their properties of porosity, tunability, modularity, crystallinity, flexibility, and long-term stability, which makes them attractive candidates for various applications. This dissertation focuses on two major studies, the first part encompasses the strategic design, preparation, and extensive studies of actinide containing MOFs (An-MOFs). This work, presented within the first two chapters, demonstrates the effective utilization of MOF modularity and versatility for radionuclide incorporation and sequestration. The highlights of the performed research include: (i) the synthesis of the first examples of actinide-based MOFs with unsaturated metal nodes necessary for the incorporation of a high actinide content within the MOF, (ii) thermodynamic studies of profoundly water-stable An-MOFs, (iii) “structural memory” effect of An-MOFs upon solvent exposure, and (iii) electronic structure studies of heterometallic multinuclear An-MOFs, prepared via metal node engineering. The fundamental knowledge gained from these studies is aimed towards developing novel waste forms for more effective nuclear waste management. The second part which is presented in the last two chapters, reveal investigative studies of the effect of the incorporation of a second metal on the electronic structure and catalytic proficiency of three distinct classes of heterometallic multinuclear MOFs. Utilizing the metal node vi engineering technique, we are able to preserve MOF porosity while tuning framework electronic structure and catalytic activity. Combination of experimental and theoretical studies of the heterometallic MOFs, for example, single crystal and powder X-ray diffraction, X-ray photoelectron spectroscopy and theoretical modeling, allowed us not just to establish the structure-property relationship of these systems, but also provide valuable insights into the improvement and expansion of MOF applications
Sequestration of Radionuclides in Metal–Organic Frameworks from Density Functional Theory Calculations
Nadia Houcke (1926-2011) et son poney Peggy
Growing
necessity for efficient nuclear waste management is a driving
force for development of alternative architectures toward fundamental
understanding of mechanisms involved in actinide (An) integration
inside extended structures. In this manuscript, metal–organic
frameworks (MOFs) were investigated as a model system for engineering
radionuclide containing materials through utilization of unprecedented
MOF modularity, which cannot be replicated in any other type of materials.
Through the implementation of recent synthetic advances in the MOF
field, hierarchical complexity of An-materials was built stepwise,
which was only feasible due to preparation of the first examples of
actinide-based frameworks with “unsaturated” metal nodes.
The first successful attempts of solid-state metathesis and metal
node extension in An-MOFs are reported, and the results of the former
approach revealed drastic differences in chemical behavior of extended
structures versus molecular species. Successful utilization of MOF
modularity also allowed us to structurally characterize the first
example of bimetallic An–An nodes. To the best of our knowledge,
through combination of solid-state metathesis, guest incorporation,
and capping linker installation, we were able to achieve the highest
Th wt % in mono- and biactinide frameworks with minimal structural
density. Overall, the combination of a multistep synthetic approach
with homogeneous actinide distribution and moderate solvothermal conditions
could make MOFs an exceptionally powerful tool to address fundamental
questions responsible for chemical behavior of An-based extended structures
and, therefore, shed light on possible optimization of nuclear waste
administration
Flipping the Switch: Fast Photoisomerization in a Confined Environment
Stimuli-responsive materials are
vital for addressing emerging
demands in the advanced technology sector as well as current industrial
challenges. Here, we report for the first time that coordinative integration
of photoresponsive building blocks possessing photochromic spiropyran
and diarylethene moieties within a rigid scaffold of metal–organic
frameworks (MOFs) could control photophysics, in particular, cycloreversion
kinetics, with a level of control that is not accessible in the solid
state or solution. On the series of photoactive materials, we demonstrated
for the first time that photoisomerization rates of photochromic compounds
could be tuned within almost 2 orders of magnitude. Moreover, cycloreversion
rates of photoresponsive derivatives could be modulated as a function
of the framework structure. Furthermore, through MOF engineering we
were able to achieve complete isomerization for coordinatively immobilized
spiropyran derivatives, typically exhibiting limited photoswitching
behavior in the solid state. For instance, spectroscopic analysis
revealed that the novel monosubstituted spiropyran derivative grafted
to the backbone of the MOF pillar exhibits a remarkable photoisomerization
rate of 0.16 s<sup>–1</sup>, typical for cycloreversion in
solution. We also applied the acquired fundamental principles toward
mapping of changes in material properties, which could provide a pathway
for monitoring material aging or structural deterioration
Flipping the Switch: Fast Photoisomerization in a Confined Environment
Stimuli-responsive materials are
vital for addressing emerging
demands in the advanced technology sector as well as current industrial
challenges. Here, we report for the first time that coordinative integration
of photoresponsive building blocks possessing photochromic spiropyran
and diarylethene moieties within a rigid scaffold of metal–organic
frameworks (MOFs) could control photophysics, in particular, cycloreversion
kinetics, with a level of control that is not accessible in the solid
state or solution. On the series of photoactive materials, we demonstrated
for the first time that photoisomerization rates of photochromic compounds
could be tuned within almost 2 orders of magnitude. Moreover, cycloreversion
rates of photoresponsive derivatives could be modulated as a function
of the framework structure. Furthermore, through MOF engineering we
were able to achieve complete isomerization for coordinatively immobilized
spiropyran derivatives, typically exhibiting limited photoswitching
behavior in the solid state. For instance, spectroscopic analysis
revealed that the novel monosubstituted spiropyran derivative grafted
to the backbone of the MOF pillar exhibits a remarkable photoisomerization
rate of 0.16 s<sup>–1</sup>, typical for cycloreversion in
solution. We also applied the acquired fundamental principles toward
mapping of changes in material properties, which could provide a pathway
for monitoring material aging or structural deterioration
Flipping the Switch: Fast Photoisomerization in a Confined Environment
Stimuli-responsive materials are
vital for addressing emerging
demands in the advanced technology sector as well as current industrial
challenges. Here, we report for the first time that coordinative integration
of photoresponsive building blocks possessing photochromic spiropyran
and diarylethene moieties within a rigid scaffold of metal–organic
frameworks (MOFs) could control photophysics, in particular, cycloreversion
kinetics, with a level of control that is not accessible in the solid
state or solution. On the series of photoactive materials, we demonstrated
for the first time that photoisomerization rates of photochromic compounds
could be tuned within almost 2 orders of magnitude. Moreover, cycloreversion
rates of photoresponsive derivatives could be modulated as a function
of the framework structure. Furthermore, through MOF engineering we
were able to achieve complete isomerization for coordinatively immobilized
spiropyran derivatives, typically exhibiting limited photoswitching
behavior in the solid state. For instance, spectroscopic analysis
revealed that the novel monosubstituted spiropyran derivative grafted
to the backbone of the MOF pillar exhibits a remarkable photoisomerization
rate of 0.16 s<sup>–1</sup>, typical for cycloreversion in
solution. We also applied the acquired fundamental principles toward
mapping of changes in material properties, which could provide a pathway
for monitoring material aging or structural deterioration
Flipping the Switch: Fast Photoisomerization in a Confined Environment
Stimuli-responsive materials are
vital for addressing emerging
demands in the advanced technology sector as well as current industrial
challenges. Here, we report for the first time that coordinative integration
of photoresponsive building blocks possessing photochromic spiropyran
and diarylethene moieties within a rigid scaffold of metal–organic
frameworks (MOFs) could control photophysics, in particular, cycloreversion
kinetics, with a level of control that is not accessible in the solid
state or solution. On the series of photoactive materials, we demonstrated
for the first time that photoisomerization rates of photochromic compounds
could be tuned within almost 2 orders of magnitude. Moreover, cycloreversion
rates of photoresponsive derivatives could be modulated as a function
of the framework structure. Furthermore, through MOF engineering we
were able to achieve complete isomerization for coordinatively immobilized
spiropyran derivatives, typically exhibiting limited photoswitching
behavior in the solid state. For instance, spectroscopic analysis
revealed that the novel monosubstituted spiropyran derivative grafted
to the backbone of the MOF pillar exhibits a remarkable photoisomerization
rate of 0.16 s<sup>–1</sup>, typical for cycloreversion in
solution. We also applied the acquired fundamental principles toward
mapping of changes in material properties, which could provide a pathway
for monitoring material aging or structural deterioration
Multifaceted Modularity: A Key for Stepwise Building of Hierarchical Complexity in Actinide Metal–Organic Frameworks
Growing
necessity for efficient nuclear waste management is a driving
force for development of alternative architectures toward fundamental
understanding of mechanisms involved in actinide (An) integration
inside extended structures. In this manuscript, metal–organic
frameworks (MOFs) were investigated as a model system for engineering
radionuclide containing materials through utilization of unprecedented
MOF modularity, which cannot be replicated in any other type of materials.
Through the implementation of recent synthetic advances in the MOF
field, hierarchical complexity of An-materials was built stepwise,
which was only feasible due to preparation of the first examples of
actinide-based frameworks with “unsaturated” metal nodes.
The first successful attempts of solid-state metathesis and metal
node extension in An-MOFs are reported, and the results of the former
approach revealed drastic differences in chemical behavior of extended
structures versus molecular species. Successful utilization of MOF
modularity also allowed us to structurally characterize the first
example of bimetallic An–An nodes. To the best of our knowledge,
through combination of solid-state metathesis, guest incorporation,
and capping linker installation, we were able to achieve the highest
Th wt % in mono- and biactinide frameworks with minimal structural
density. Overall, the combination of a multistep synthetic approach
with homogeneous actinide distribution and moderate solvothermal conditions
could make MOFs an exceptionally powerful tool to address fundamental
questions responsible for chemical behavior of An-based extended structures
and, therefore, shed light on possible optimization of nuclear waste
administration
Multifaceted Modularity: A Key for Stepwise Building of Hierarchical Complexity in Actinide Metal–Organic Frameworks
Growing
necessity for efficient nuclear waste management is a driving
force for development of alternative architectures toward fundamental
understanding of mechanisms involved in actinide (An) integration
inside extended structures. In this manuscript, metal–organic
frameworks (MOFs) were investigated as a model system for engineering
radionuclide containing materials through utilization of unprecedented
MOF modularity, which cannot be replicated in any other type of materials.
Through the implementation of recent synthetic advances in the MOF
field, hierarchical complexity of An-materials was built stepwise,
which was only feasible due to preparation of the first examples of
actinide-based frameworks with “unsaturated” metal nodes.
The first successful attempts of solid-state metathesis and metal
node extension in An-MOFs are reported, and the results of the former
approach revealed drastic differences in chemical behavior of extended
structures versus molecular species. Successful utilization of MOF
modularity also allowed us to structurally characterize the first
example of bimetallic An–An nodes. To the best of our knowledge,
through combination of solid-state metathesis, guest incorporation,
and capping linker installation, we were able to achieve the highest
Th wt % in mono- and biactinide frameworks with minimal structural
density. Overall, the combination of a multistep synthetic approach
with homogeneous actinide distribution and moderate solvothermal conditions
could make MOFs an exceptionally powerful tool to address fundamental
questions responsible for chemical behavior of An-based extended structures
and, therefore, shed light on possible optimization of nuclear waste
administration