Document Type
Dissertation
Date of Award
2026
Degree Name
Doctor of Philosophy (PhD)
Department
Chemistry
First Advisor
Zhenqiang Z Wang
Abstract
Porous materials that feature well-defined nanocavities have garnered significant interest due to their potential applications in a wide range of areas including chemical separation, gas storage, catalysis, chemical sensing, and drug delivery. In this research, we introduce a new class of porous molecules, namely, metal-organic supercontainers (MOSCs), which feature both intrinsic and extrinsic porosities, in the form of endo and exo cavities, suitable for trapping, transporting, and transforming other guest molecules. The overarching goal of this dissertation is to employ synthetic manipulations to modify the hierarchical porosities of MOSC in solid and liquid states, thereby enhancing their functional applications. To achieve this goal, we designed a new family of MOSCs by the self-assembly of salicylhydroximate (Shi), dicarboxylate linkers, Ga(III) and lanthanide(III) ions. Gas adsorption studies suggest that molecular solids of Shi-MOSCs are nonporous when analyzed with N2 adsorption at 77 K, yet exhibit favorable and in some cases selective uptake of other guest molecules such as water, acetone, carbon dioxide and refrigerants, which can be attributed to their inherent flexibility termed as adaptive porosity. Adaptive porosity refers to the porosity that is induced in host molecules by the presence of suitable guest species. It arises when host molecules are flexible enough to expand or contract, thus altering their intrinsic/extrinsic porosity in response to guest species. For instance, Shi-MOSCs functionalized with hydrogen-bonding -NH2 groups in carboxylate linkers are nonporous as they lack accessible porosity but display significant water uptake with well-defined S-shaped isotherm due to their flexible packing i.e., extrinsic porosity, highlighting their potential as promising materials for dehumidification. Additionally, anionic MOSCs can be modified with suitable counter cations (e.g., Na+) to customize their extrinsic porosity and enhance uptake of refrigerants such as difluoromethane (R-32) while maintaining selectivity over pentafluoroethane (R-125), illustrating their potential in refrigerant separation. Furthermore, solution studies indicate that anionic MOSCs featuring open metal (Ga3+) sites show selective binding of fluoride ions, attributed to their accessible molecular porosity and favorable interactions with the Lewis acidic metal centers. Collectively, these results highlight the versatility of MOSCs and demonstrate how targeted synthetic modifications can be used to precisely tune their porosity and functionality, enabling diverse applications across solid-state and solution-phase systems.
Subject Categories
Chemistry
Keywords
None Provided
Number of Pages
170
Publisher
University of South Dakota
Recommended Citation
Chitrakar, Kriti, "Hierarchical Porosities in Metal-Organic Supercontainers" (2026). Dissertations and Theses. 445.
https://red.library.usd.edu/diss-thesis/445