This Ph.D. project focused on metal-organic frameworks (MOFs) and their environmental and energy technologies applications. MOFs combine tunable light-harvesting and catalytic functions with excellent reactant adsorption capabilities. For dynamic processes in the liquid phase, the accessibility of active sites becomes a critical parameter as the inherently small micropores limit reactant diffusion. In this work, I developed a strategy to introduce additional mesopores by selectively removing one ligand in mixed-ligand MOFs via thermolysis. Accordingly, photoactive MOFs of the MIL-125-Ti family were designed with two distinct hierarchical pore architectures resembling either large cavities or branching fractures. The samples were characterized by a broad set of ex situ and in situ techniques (X-ray diffraction analysis (XRD), Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS), Nuclear magnetic resonance spectroscopy (NMR), supported by density functional theory (DFT) simulations. The ligand removal follows a 2-step process tunable by temperature and time. Both pore geometries significantly improved the HER rates of the MOFs by up to 400%. This strategy provides a new tool for the purposeful engineering of hierarchical MOFs with advanced applicability in liquid media. Moreover, the impact of selective ligand removal on heat-treated MOFs was investigated on the adsorption of contaminants from water. It is desirable to create novel adsorbents with high adsorption capabilities for the adsorptive removal of hazardous components of organophosphorus pesticides (OPs). In this work, I synthesized MIL-125-Ti, NH2-MIL, 2%NH2-MIL, and their heat-treated versions and examined their performance, kinetics and mechanism for the adsorption of glyphosate (N-(phosphonomethyl)glycine, abbreviated as PMG) from water. Due to their strong affinity for phosphoric groups, the numerous Ti–OH groups resulting from the selective ligand removal acted as natural anchorages for effective glyphosate uptake. The relationship between the most important factors, such as contact duration, OPs concentration, and adsorbent dosage, was investigated, and the impact of these parameters on glyphosate removal effectiveness from contaminated aqueous solution examined. Adsorption capacities of heat-treated MOFs exceeded 440.91 mg g-1 due to strong affinity and appropriate pore size, which ranks these MOFs among the best reported adsorbents. This work also introduces two environmental friendly mixed-ligand Cu-based frameworks (MOFs), Cu2(Hbtc)2(bpe)2(bpe) where bpe refers to 1,2-bis(4-pyridyl)ethane and Hbtc to benzene-1,3,5-tricarboxylat and Cu2(Hbtc)2(bpy)2(H2O)2]·(bpy) where bpy referes to 4,4’-bipy, denoted as TUW-1 and TUW-2 respectively. These MOFs were also tested as adsorbents for fast and highly effective nitrate removal from water and real wastewater. Moreover, these new MOFs are currently the most stable MOFs in water with structural stability confirmed up to at least 200 days. Both MOFs show the currently fastest adsorption kinetics and highest capacity of nitrate adsorption (119.42 mg g-1 for TUW-1 and 105.93 mg g-1 for TUW-2) among all reported adsorbents, even at neutral pH values.
Shaghayegh Naghdi (Fri,) studied this question.