Doctor of Philosophy (Ph.D.)
Degree Granting Department
Shengqian Ma, Ph.D.
James Leahy, Ph.D.
John Kuhn, Ph.D.
Brian Space, Ph.D.
Arash Takshi, Ph.D.
Pore Surface Engineering, Porous Materials, Task-Specific Design, Transition Metals
Linking small organic molecules into an extended solid usually afford disordered amorphous polymers. The instigation of order into such a material is of profound interest to induce inherent fine control of the overall structure. Covalent organic frameworks (COFs) are new class of porous crystalline material prepared by connecting organic building blocks via strong covalent bonds. The judicious choice of organic monomers can give rise to highly ordered and predictable frameworks with high crystallinity, surface area, and thermal/chemical stability. The role of connecting linkages such as B─O, C─C, C─N extends the principle of fundamental molecular covalent chemistry to the formation of crystalline materials. Among the diverse family of organic building blocks, bipyridine, catechol, and 2-phenylpyridine has gained attraction as organic monomer due to its excellent binding affinity with various transition metal ions. The metal ions, vanadium, palladium, and iridium were adopted to construct modified hybrid porous materials through pore surface engineering of frameworks.
In this dissertation, the role of pore surface engineering in covalent organic frameworks to form hybrid porous materials as heterogeneous catalysts for critical organic and organometallic conversions are demonstrated. Vanadium-modified frameworks (VO-TAPT-2,3-DHTA and VOPyTTA-2,3-DHTA) were synthesized by the reaction of catechol decorated COFs (TAPT-2,3-DHTA and PyTTA-2,3-DHTA) with vanadyl acetylacetonate. The hybrid porous materials serve as effective heterogeneous catalysts for Prins reaction, modified Mannich-type reaction, and sulfide oxidation (chapter 2). In addition to catechol decorated framework, bipyridine functionalized, Py-2,2´-BPyPh COF was used as scaffold to successfully immobilize iridium metal ions (Ircod(I)@Py-2,2´-BPyPh COF) to significantly broaden the spectrum of metal binding in this field. Ircod(I)@Py-2,2´-BPyPh COF acts as a reusable and recyclable catalyst for an effective C─H borylation reactions (chapter 3). The penultimate chapter of the dissertation illustrate an insight of metal docking via post synthetic modification of controllable bipyridine content of dual-pore imine-linked [(BPyDC)]x%-ETTA COFs (x = 0%, 25%, 50%, 75%, 100%), thereby imparts controlled palladium immobilization through binding with bipyridine units. The dual-pore palladium docked framework used as catalyst for C─H to C─O and C─X (X = Br, Cl) functionalization, which was compared with single pore palladium immobilized COF, Pd(II)@Py-2,2´-BPyPh to establish structure function relationship. Finally, in the last chapter of dissertation, first ever palladium-assisted intramolecular C─H functionalization, namely C─X (X = Cl, Br), C─O, and C─C within 2-phenylpyridine decorated PyTTA-FPPY framework is summarized.
Characterization of the pristine and modified porous frameworks includes powder X-ray diffraction (PXRD), surface area measurement at 77 K, thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), solid state 13C CP-MAS NMR, scanning electron microscopy (SEM), transmission electron microscopy (TEM), elemental analysis, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and electron paramagnetic resonance spectroscopy (EPR). In addition, intramolecular C─H functionalization were also studied by electrospray ionization-mass spectrometry (ESI-MS), and high-performance liquid chromatography (HPLC), which may provide ample opportunities to develop novel covalent organic framework, which are difficult to synthesize via de novo synthesis.
Scholar Commons Citation
Vardhan, Harsh, "Covalent Organic Frameworks as an Organic Scaffold for Heterogeneous Catalysis including C-H Activation" (2020). USF Tampa Graduate Theses and Dissertations.