Abstract |
This thesis delves into the study of reticular chemistry, specifically the chemistry
of metal-organic frameworks (MOFs). First, we study the complex behavior of the
third generation of MOFs, the dynamic/flexible MOFs. We report the synthesis and
characterization of a chemically robust, flexible microporous MOF based on a
functionalized carboxylate linker, a diamine linker, and nickel. This material has been
thoroughly characterized, focusing on its vapor sorption capabilities. Notably, in the
case of polar vapors, the material displays a stepwise sorption isotherm associated
with framework flexibility. On the other hand, non-polar vapors are not being
adsorbed, indicating a high selectivity towards the polar ones. Pre-synthetic and
post-synthetic modification procedures using this MOF as a base, with the diamine
linker or metal substitution, led to the formation of five more MOF materials of which
the flexible behavior, if any, was investigated. Moreover, another flexible MOF was
synthesized based on the same functionalized carboxylate linker with manganese.
This structure possessed many coordinated solvent molecules, and their substitution
by other solvent molecules led to a non-reversible structural transformation. Despite
that, this MOF proved to possess a higher affinity toward the sorption of more polar
vapors. The flexible behavior of the MOFs investigated in this work proved to be
important for industrial-level gas storage and gas separation applications among
many other potential applications. In a different study, we utilized the isoreticular
expansion technique to explore the creation of MOFs with an extended tetratopic
bicarbazole linker as a building block. Our goal was to construct porous structures
with larger cavities and more porosity. We experimented with various metal sources
but only managed to produce either microcrystalline, microporous MOF structures or
interpenetrated ones. This extension of the linker by adding aromatic rings introduces
strong π-π interactions between the molecules, and makes them less soluble in most
MOF synthesis solvents. Moreover, using this linker favors the formation of
interpenetrated frameworks due to the strong π-π interactions and large cavities
created. We solved these challenges by adding methyl groups to the extended linker,
increasing its solubility in the solvents used in MOF synthesis, and decreasing the
probability of forming interpenetrated frameworks. We created two new MOF
structures using zirconium and yttrium, with the zirconium-based MOF containing the
first in literature 16-connected Zr6 cluster. Our findings show that adding alkyl groups
during MOF synthesis can reduce the problems of solubility of the ligand, and
formation of interpenetrated frameworks, leading to the discovery of novel MOFs with
larger cavities and higher porosity that can address many important energy
problems.
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