PhD in chemistry (M/F) – Bridging Innovative Coordination complexes of Earth-abundant metals for efficient Photocatalysis

The reckless consumption of fossil fuels has propelled pollution to alarming levels. Notably, industrial activities have resulted in the substantial accumulation of carbon dioxide in the atmosphere, contributing significantly to the ongoing global warming crisis. Given the improbable prospect of a near-term reduction in global CO2 production, it becomes imperative to design systems capable of valorizing CO2 (1). This is particularly crucial in the context of ensuring the sustained viability of life on Earth. In this context, a very promising method is to perform the reduction of CO2 into added value carbon-based compounds, such as CO or methanol.

However, the reduction of CO2 is a very energy demanding chemical process because it is a remarkably stable molecule. In other words, the energy cost to reduce CO2 is so high that is cannot be achieved in a sustainable way. 

How then is it possible to perform CO2 reduction, all through a sustainable green process?

By solving two main problems: decreasing the energy cost, and finding a renewable source of energy to drive the reactions.

Problem 1 can be partially solved through the principles of chemical catalysis, using well-defined molecular CO2 reduction catalysts (MCCO2) which can decrease high activation barriers (2). As regards problem 2, light is a natural, free, democratic source of energy. To domesticate the energy of photons, the use of molecular photosensitizers (PS) is often necessary (3), as exemplified in many photochemical processes (the most famous example being of course chlorophylls as PS in natural photosynthesis). 

Unfortunately, MCCO2 and PS are often complexes of rare earth metals like ruthenium, palladium, rhodium, and rhenium. The scarcity of these elements generates geopolitical problems, incompatible with the envisioned sustainable approach. 

The joint Franco-American project BICEPS aims at addressing both problems by covalently linking MCCO2 with PS, all exclusively based on Earth abundant metal species. More precisely, Nickel-cyclam based MCCO2 are chosen because of their efficiency and selectivity (4). As regards PS, copper(I)-phenanthroline complexes are selected because of their spectacular excited state reactivity, particularly adapted to reduction processes (5).

1             A. M. Appel, J. E. Bercaw, A. B. Bocarsly, H. Dobbek, D. L. DuBois, M. Dupuis, J. G. Ferry, E. Fujita, R. Hille, P. J. A. Kenis, C. A. Kerfeld, R. H. Morris, C. H. F. Peden, A. R. Portis, S. W. Ragsdale, T. B. Rauchfuss, J. N. H. Reek, L. C. Seefeldt, R. K. Thauer and G. L. Waldrop, Chem. Rev., 2013, 113, 6621–6658.

2             E. Boutin, L. Merakeb, B. Ma, B. Boudy, M. Wang, J. Bonin, E. Anxolabéhère-Mallart and M. Robert, Chem. Soc. Rev., 2020, 49, 5772–5809.

3             J. W. Tucker and C. R. J. Stephenson, J. Org. Chem., 2012, 77, 1617–1622.

4             J. D. Froehlich and C. P. Kubiak, Inorg. Chem., 2012, 51, 3932–3934.

5             L. Gimeno, C. Queffélec, K. Mall Haidaraly, E. Blart and Y. Pellegrin, Catal. Sci. Technol., 2021, 11, 6041–6047.

The PhD will consist in synthesizing a set of PS-Linker-MCCO2 molecular dyads based only on earth-abundant systems where the length, the nature and the position of the linker between PS and MCCO2 will be varied consistently in order to provide a clear, definitive rationale on the long-sought after structure-reactivity relationships in photosensitive dyads. The US partner will be in charge of studying the structures and photocatalytic properties of the obtained PS-Linker-MCCO2 systems. 

The project will take place in the Chemistry And Interdisciplinarity, Synthesis, Analysis, Modeling (CEISAM) laboratory. It is part of a collaboration with Dr. Gonghu Li from the University of New Hampshire. As part of the PhD program, one-month research stays will be planned each year in Prof. Gonghu Li’s laboratory in the United States.

Nantes Université is a recognized institution and a major research center in Western France. With 42 000 students and 3 200 lecturers and researchers, Nantes Université seeks to meet today's major challenges. Located near the Atlantic coast and 2 hours from Paris by train, Nantes is a large city regularly ranked for its quality of life and well-known for its cultural scene.

PhD students in physics, chemistry and geosciences receive training in internationally recognized laboratories associated with the CNRS. They also benefit from a wage of €2 200 gross per month. Within the Graduate School 3MG, students are able to attend courses dedicated to research and innovation and take part in events and meetings in France or abroad to develop their professional network.

The candidate should have prior experience in organic and/or organometallic chemistry and a strong interest in catalysis and photocatalysis. They should demonstrate curiosity, strong motivation, enthusiasm, and autonomy. Good communication skills (both written and oral) are also expected.