Metal Organic Frameworks: Explorations and Design Strategies for MOF Synthesis
KAUST DepartmentPhysical Sciences and Engineering (PSE) Division
Permanent link to this recordhttp://hdl.handle.net/10754/621964
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AbstractMetal-Organic Frameworks (MOFs) represent an emerging new class of functional crystalline solid-state materials. In the early discovery of this now rapidly growing class of materials significant challenges were often encountered. However, MOFs today, with its vast structural modularity, reflected by the huge library of the available chemical building blocks, and exceptional controlled porosity, stand as the most promising candidate to address many of the overbearing societal challenges pertaining to energy and environmental sustainability. A variety of design strategies have been enumerated in the literature which rely on the use of predesigned building blocks paving the way towards potentially more predictable structures. The two major design strategies presented in this work are the molecular building block (MBB) and supermolecular building block (SBB) -based approaches for the rationale assembly of functional MOF materials with the desired structural features. In this context, we targeted two highly connected MOF platforms, namely rht-MOF and shp-MOF. These two MOF platforms are classified based on their topology, defined as the underlying connectivity of their respective net, as edge transitive binodal nets; shp being (4,12)-connected net and rht being (3,24)-connected net. These highly connected nets were deliberately targeted due to the limited number of possible nets for connecting their associated basic building units. Two highly porous materials were designed and successfully constructed; namely Y-shp-MOF-5 and rht-MOF-10. The Y-shp-MOF-5 features a phenomenal water stability with an exquisite behavior when exposed to water, positioning this microporous material as the best adsorbent for moisture control applications. The shp-MOF platform proved to be modular to ligand functionalization and thus imparting significant behavioral changes when hydrophilic and hydrophobic functionalized ligands were introduced on the resultant MOF. On the other hand, rht-MOF-10 constituting of 24-connected transition metal based-SBB was successfully synthesized and activated using a modified supercritical CO2 drying technique. This allowed access to over 90 % of the total pore volume (1.95cm3/g). High pressure gas sorption measurements of CH4, CO2 and O2 showed that this material has a gravimetric uptake that ranks close to the best materials enlisted for the storage of these corresponding gases.