Enantioselective Catalysis and Nitrogen Reduction Promoted by Visible Light With Abundant Dyes and Catalysts.

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Approximately 180 million tons of NH3 were produced in 2016 using the Haber-Bosch process. The Haber-Bosch (H-B) process requires high T, P, H2, and it accounts for ~2% of the worldwide annual energy consumption by utilizing methane steam reforming (MSR) to produce H2. H-B presently emits ~ 2 tons CO2/ton NH3, plus additional greenhouse gases through fugitive methane leaks. The photoelectrochemical nitrogen reduction reaction (NRR) is a promising carbon-zero method to produce NH3 fertilizer. As well, liquid NH3 is a highly promising medium to store and transport renewable energy. This proposal will develop new Earth-abundant nanoparticle catalysts for the electrochemical NRR. We will also incorporate known electrochemical, photochemical, and photoelectrochemical NRR catalysts with the highest faradic or quantum yields, and that are Earth-abundant and easy to prepare. The proposal will develop new strategies to incorporate the NRR catalysts with our new derivatives of the organic chromophore 2,4,5,6-tetra(9H-carbazol-9-yl)isophthalonitrile, 4CzIPN. 4CzIPN is a recent, important photocatalyst for photoredox- and energy transfer organic photoreactions. 4CzIPN is also being investigated in organic light-emitting diode displays. The derivatives we will study include NH2-CzIPN, with an amine group at the 3-position of the 5-carbazole group; IMID-CzIPN, with 1-imidazole at the 5-position of the IPN ring; BnzIMID-CzIPN, with 3-benzyl-1-imidazolium at the 5-position of the IPN ring, and NHC-CzIPN, the corresponding free N-heterocyclic carbene. We note that NHC-CzIPN is the first example of an NHC ligand containing the CzIPN photocatalyst. The NRR catalysts and the new CzIPN-based chromophores will be incorporated into NRR photocathodes using diazonium electrografting, NHC coordination to Mo, H-bonding for bifunctional N2 activation, and carbazole electropolymerization. For example, the first dithiourea photocatalysts based upon CzIPN will be prepared in one step from NH2-CzIPN using established isothiocyanate chemistry. These dithioureas will be utilized to photoreduce and activate N2 in a new bifunctional manner with H-bonding acting synergistically with N2 coordination to Mo. The supports will be carbon fibre or ITO nanoparticles or nanorods. The new electrocatalysts and modes of activation can also be applied to the direct electrochemical NRR reaction powered by photovoltaics. New chiral dithiourea photocatalysts will also be prepared from NH2-CzIPN and utilized as H-bonding organic photocatalysts for enantioselective intra- and intermolecular-[2+2]-photocycloaddition reactions including the DeMayo reaction. As well, cobaloxime-NHC-CzIPN compounds will be developed as abundant photocatalysts for olefin decarboxylation and imine cross coupling reactions. The long-term plans are to develop a series of earth abundant TM-CzIPN photocatalysts.