Solar Nitrogen Fixation

• Applicants: Privatdozent Dr. Vincent Artero; Professor Dr. Christoph Bostedt; Professorin Dr. Vera Krewald; Professor Dr. Sven Schneider
• Subject Area: Technical Chemistry ; Inorganic Molecular Chemistry - Synthesis and Characterisation ; Physical Chemistry of Molecules, Liquids and Interfaces, Biophysical Chemistry ; Theoretical Chemistry: Electronic Structure, Dynamics, Simulation
• Term: since 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 428767511

The efficient activation of the extremely strong N-N triple bond at ambient conditions is a fundamental challenge in chemistry with wide-ranging implications. Ammonia (NH3), which is industrially derived from dinitrogen via the energy-intensive, fossil resource-consuming Haber-Bosch process, is the sole nitrogen source for the production of fertilizers and chemicals and has potential as a fuel in chemical energy storage schemes. A carbon-neutral, environmentally friendly nitrogen fixation strategy is thus an important goal for a green energy economy and sustainable industrial production. Herein, we propose several light-driven schemes for the activation of dinitrogen and the production of ammonia with molecular complexes. The key concept is to overcome thermodynamic and/or kinetic bottlenecks within the 6-electron/6-proton transformation from dinitrogen to ammonia with molecular catalysts by targeted deposition of light as energy source. Expanding on sporadic and largely heuristic reports of molecular N2 photoactivation, this project will follow two strategies, depending on the nature of the catalyst used: (I) light-driven N–H formation by photo-PCET with molecular photosensitizer dyads; (II) light-driven N2 splitting into molecular nitrides with enhanced quantum yields by excited state trapping.These concepts will be realized and validated by a joint synthetic, (time-resolved) spectroscopic and computational approach. Based on our electronic structure model for N2 splitting, transition metal complexes with tailorable pincer ligands (V. Artero, Grenoble; S. Schneider, Göttingen) will be utilized as molecular platforms to synthesize key species for N2 fixation and examine the proposed approaches. Their validation will be substantiated by detailed examination of the photophysics and -chemistry using state-of-the-art femtosecond pump-probe spectroscopies in the visible light and X-ray domains (C. Bostedt, Villingen/Lausanne), and ab initio quantum chemical analyses of their ground and excited state electronic structures and dynamic behavior (V. Krewald, Darmstadt). The aim of the proposed project is to understand the fundamental physical and chemical principles of photochemical nitrogen fixation as a foundation for the systematic development of light-driven catalysis

• DFG Programme: Research Grants
• International Connection: France, Switzerland
• Partner Organisation: Agence Nationale de la Recherche / The French National Research Agency; Schweizerischer Nationalfonds (SNF)