Charge Transport, Electro, and Organic Photoredox Catalysis in Metal-Organic Frameworks

Author

Karan Maindan, Southern Illinois University CarbondaleFollow

Date of Award

5-1-2022

Degree Name

Master of Science

Department

Chemistry

First Advisor

Deria, Pravas

Abstract

This thesis documents efforts to synthesize Metal-Organic Frameworks (MOFs) and study their charge transport, electrocatalytic, and photoredox catalytic properties. Chapter 1 introduces concepts of pre-synthetic and post-synthetic metalation of MOFs. A series of four chemically identical but structurally different hydrolytically robust ZrIV-MOFs constructed from tetrakis(4-carboxyphenyl) porphyrinato iron (III) are examined to understand the influence of topological construction on redox hopping conductivity. The structural variation fixes center-to-center distances in the four MOFs and defines the hopping rate. The spin-state variation of the central metal in the porphyrin unit helps in further tuning the TCPP(FeIII/II) reorganization energy of the self-exchange process. The hopping rate significantly increased upon axial coordination of 1-methyl imidazole to the iron center, which converts a weakly halide bound five-coordinated high-spin (HS) TCPP(FeIII/II) to the six-coordinated low-spin (LS) complex. The population of LS vs HS species is shown to be a function of topology in the presence of an excess ligand. Chapter 2 investigates this idea further by using MOFs for electrocatalytic oxygen reduction reaction (ORR). Two cobalt-centered porphyrin-based MOFs are synthesized and deposited on various substrates to afford working electrodes that can be used in an electrochemical cell to catalyze the ORR. Chapter 3 investigates the linker-dependent photoredox catalytic activity of MOFs that possess the same topology. This is the first MOF-based study wherein a heavy metal like ruthenium is not employed to carry out the visible light-dependent photoredox catalysis.