Research

Our research focuses on the development of novel molecular systems, catalysts and materials for sustainable synthetic methods, electrochemical energy storage and recycling processes. We combine preparative organic and organometallic chemistry with spectroscopic, electrochemical and computational methods. Our current research areas build on earlier work on chiral ionic liquids, camphor-derived carbenes and functionalized carbon nanomaterials. Research on ionic and photoactive molecules, sustainable catalysis and carbon-based materials provided the foundation for our present projects in photoredox catalysis, asymmetric NHC catalysis, electrochemical energy storage and the reuse of battery graphite.

We develop organic and metal-complex-based photoredox catalysts for the activation and selective functionalization of organic molecules using visible light. These systems include diquat- and viologen-based organic photocatalysts as well as bichromophoric ruthenium complexes. A particular focus is placed on tailoring their redox properties, absorption in the visible region and the lifetimes of their photoexcited states. The resulting catalysts are employed in C–C, C–N and C–S bond-forming reactions, including the late-stage functionalization of heteroaromatic compounds. Mechanistic investigations and quantum-chemical calculations are used to elucidate the underlying electron- and energy-transfer processes and to support the rational development of the catalytic systems.

For aqueous organic redox-flow batteries, we develop highly water-soluble, electrochemically reversible redox-active molecules that are stable over extended periods. Our work focuses particularly on viologen-based negolytes, triarylamine-based bipolar molecules and cationic ferrocene derivatives. In addition to synthesizing new electrolyte molecules, we investigate their redox potentials, diffusion coefficients, solubility, chemical stability and behaviour under practically relevant cell conditions. Our objective is to develop safe and resource-efficient stationary energy-storage systems based on organic materials.

Starting from camphor as an inexpensive and readily available member of the chiral pool, we develop novel chiral N-heterocyclic carbenes and multidentate NHC ligands. The incorporation of additional nitrogen, sulfur or oxygen donor groups allows the coordination properties and the steric environment around the metal centre to be systematically modified. The corresponding rhodium, ruthenium and copper complexes are investigated in stereoselective and asymmetric catalytic transformations. Current research focuses on rhodium(I)-catalysed asymmetric ring-opening reactions of bicyclic alkenes and copper-catalysed stereoselective hydrosilylation and aminosilylation reactions.

We investigate the recovery and reuse of graphite from spent lithium-ion batteries. Our research covers the separation and purification of anode graphite, its non-covalent and covalent functionalization, and its exfoliation to produce few-layer graphene materials. The recovered and modified graphite materials are characterized with respect to their structural, electrochemical and surface properties. Potential applications include their reuse as anode materials, their incorporation into lithium–sulfur batteries and their utilization as functional carbon materials.

Another area of our research concerns chemical and catalytic methods for recycling cross-linked polymers and carbon-fibre-reinforced plastics. The objective is to recover high-quality fibres and valuable chemical building blocks under conditions that are as mild and resource-efficient as possible.

We gratefully acknowledge the institutions listed below for their current or previous financial support of our research.