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Abstract
Metal-organic frameworks (MOFs) are an emerging class of hybrid molecular materials
with extended structures constructed from inorganic metal nodes/ions interconnected with
multidentate organic linkers. They have been explored in a broad range of applications owing to
their modular nature. However, MOFs suffer from restricted diffusion of substrates and products
through relatively small channels. To overcome diffusional limitation, our group recently reduced
the thickness of one dimension of MOFs to a monolayer to afford a new class of hybrid materials,
metal-organic layers (MOLs). This dissertation focuses on the development of new MOFs and
MOLs for sensing and catalytic applications.
The first part (Chapter 1) of this dissertation focuses on rational design of MOFs for oxygen
sensing. We developed a novel strategy of using mixed ligands of very different chemical nature
to construct functional MOFs. Using this method, we synthesized a phosphorescence/fluorescence
dual-emissive nanoscale metal-organic framework (nMOF) as an intracellular oxygen sensor. The
nMOF contains a Pt(II)-porphyrin ligand as an O2-sensitive probe and a Rhodamine-B
isothiocyanate (RITC) ligand as an O2-insensitive reference probe, and exhibits good crystallinity,
high stability, and excellent ratiometric luminescence response to O2 partial pressure. In vitro
experiments confirmed the applicability of this nMOF as an intracellular O2 biosensor.
The second part (Chapter 2-4) of the dissertation reports the synthesis of functional MOLs
as novel single-site solid catalysts for a variety of organic transformations. MOLs overcome
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substrate size and diffusion limitations often seen in MOFs owing to their unique monolayer
structures. We demonstrated the superior performance of MOLs over MOFs in many catalytic
reactions. In Chapter 2, we incorporated Ru(bpy)32+ photosensitizer into BPY-MOL via post
synthetic metalation to afford photoactive RuBPY-MOL. RuBPY-MOL exhibits higher efficacy
than RuUiO-67 in multicomponent photoreactions such as intramolecular and crossed [2+2]
photocyclization of bis(enones) and photocatalytic Meerwein addition reactions. In Chapter 3, we
report the synthesis of IrBPY-MOL containing cyclometalated iridium complex. IrBPY-MOL was
an efficient catalyst for photopolymerization of methyl methacrylate (MMA), benzyl methacrylate
(BnMA) and tert-butyl methacrylate (tBuMA). The resulting polymers possessed high-number
average molar masses and low polydispersity indices. We also showed that IrBPY-MOL
significantly outperformed IrUiO-69 MOF. In Chapter 4, we immobilized enantiopure pybox
ligand onto the SBUs of MOLs through ligand exchange. The resultant pybox-MOLs functioned
as heterogeneous asymmetric catalysts of A3-coupling reaction (aldehyde-alkyne-amine) in good
yields and high enantioselectivities.