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Broadening the Application of Organic Molecular Materials in Photocatalysis, Gas Separation and Photo-responsive Graphene-based Transistors
In the last century, organic molecular materials have been extensively explored and utilized due to their highly tailored structure and property. Organic dyes, which possess unique chromophores and rich optoelectronic properties, are promising candidates for host-guest interaction and energy conversion of photon. In combination with recently developed concepts in photo(redox) catalysis, porous organic frameworks (POFs) and field-effect transistors (FETs), the application of organic dyes is significantly broadened. In Part I, photocatalysts based on pyrene derivatives and donor-acceptor (D-A) fluorophores are developed for photo(redox) catalysis. Forming “π-hole–π” complex between pyrene-based catalysts and polyfluoroarenes, the hydrodefluorination reaction is promoted by inner-sphere electron transfer under the irradiation of household compacted fluorescent lamp. Comprehensive studies on reaction mechanism were conducted, including crystallography, NMR titration, and varying the steric hindrance of the photocatalysts as well as the substrates. D-A fluorophores with carbazole/diphenylamine donor and (di)cyanobenzene acceptor are developed as photosensitizers for efficient energy transfer (EnT) photocatalysis. Combining the finetuned accessibility of locally excited and charge transfer triplet states, as well as excited state photoredox property, D-A fluorophore is an effective design principle for the identification of new photosensitizers for EnT-based reactions. In Part II, azobenzene moieties are incorporated in POFs and graphene-based FETs for selective gas separation and photoswitchable electronics, respectively. Two azo-POFs were successfully synthesized by zinc-mediated reductive homo-coupling from tetrakis-nitro monomers. Compared to the ethylene analogs (ene-POFs), azo-POFs show enhanced CO2 uptake (up to 52 %) and CO2/N 2 selectivity (up to 59 %). In another project, multilayer azobenzene moieties were deposited on graphene surfaces with tunable thickness utilizing in situ generated aryl diazonium cations. Cis and trans forms of azobenzene are achieved by irradiation with UV and visible light, respectively, which enables reversible optically tunable change in the doping level of graphene. Bilayer graphene devices show not only robust photoswitching but also preserved conductivity and charge carrier mobilities upon chemical functionalization, which is not the case for monolayer graphene devices.
Lu, Jingzhi, "Broadening the Application of Organic Molecular Materials in Photocatalysis, Gas Separation and Photo-responsive Graphene-based Transistors" (2018). ETD collection for University of Nebraska - Lincoln. AAI10841864.