Metal–organic frameworks (MOFs) are newly emerging inorganic–organic hybrid porous materials with diverse crystalline structures, high surface areas, and tunable pores. This dissertation primarily focuses on design and synthesis of MOFs as well as the development of synthetic methodologies to target stable MOFs with desired functionalities.
In the second section, a linker exchange strategy was developed as a route to functionalize a mesoporous MOF, PCN-333, through thermodynamic control. This strategy allowed a facile incorporation of a variety of functional groups into the mesoporous MOF without compromising integrity of the parent MOF.
In the third section, a dual-exchange method was studied using a sequential linker exchange and metal metathesis on PCN-333(Fe) to achieve a chemically robust mesoporous Cr-MOF with desired functional group. Dual exchange showed the potential of this method to be a general approach to highly stable Cr-MOFs with desired functional groups upon selection of appropriate MOF template.
In the fourth section, a new Zn-MOF, SO-PCN, was designed and synthesized as a host of two dye linkers. SO-PCN showed energy transfer between the 2D porphyrinic photosensitizer layer and the photochromic switch pillar in the framework. Using photochromic reaction of the linker in SO-PCN, a reversible control of singlet oxygen generation was demonstrated. The catalytic activity of SO-PCN was also studied for photooxidation of 1,5-dihydroxynaphthalene.
In the fifth section, a new synthetic strategy to incorporate multiple functional molecules within the MOF nanoparticles was demonstrated for control of 1^O2 generation for PDT. This strategy was developed to improve several inherent limitations from SOPCN in the previous section. First, a Zr-MOF nanoplatform showed much improved stability in aqueous media, compatible under physiological conditions. This strategy allows for tuning of the ratios between the photosensitizer and the switch molecule within the Zr-MOF nanoparticles, thus enabling maximization of the 1^O2 generation controllability. As a result, MOF nanoparticle formulation showed an enhanced PDT efficacy with superior 1^O2 control compared to that of homogeneous molecular analogues.
In the sixth section, size-controlled synthesis of Zr-based porphyrinic MOF nanoparticles was studied through a bottom-up approach. The study provided mechanistic insights about the size control of the porphyrinic Zr-MOF nanoparticles. Size-dependent cellular uptake and ensuing PDT efficacy were also investigated to optimize the size of the MOF nanoparticles for PDT. Additionally, folic acid modification on the Zr6 node in the MOF showed further enhanced PDT efficacy via active targeting, demonstrating multifunctional MOF nanoplatform.
In summary, methodologies to allow functionalization of highly stable MOFs have been designed and studied. Conceptual utilizations of MOF nanoparticles for biomedical applications have also been demonstrated with stable MOF nanoparticles, showing the advantages of the MOF formulation. The findings in this dissertation provide design principle and possible options for preparing targeted MOFs as required in desired applications
