A surface science approach toward ligand-directed SCILLs

• Applicant: Professor Dr. Jörg Libuda
• Subject Area: Physical Chemistry of Solids and Surfaces, Material Characterisation
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 564993821

This project explores an innovative concept in heterogeneous catalysis: the "ligand-directed SCILL," which merges the principles of "Solid Catalysts with Ionic Liquid Layers" (SCILL) and ligand-directed catalysis. SCILLs represent a significant milestone in heterogeneous catalysis, having rapidly advanced to industrial application. They consist of supported catalysts coated with ionic liquid (IL) layers that act as catalytic modifiers, leading to notable improvements in selectivity. However, current applications predominantly utilize simple ILs, which starkly contrasts with their immense chemical versatility. ILs, in fact, can be tailored to incorporate almost any functional group into their molecular structures. Such functional groups are commonly employed in ligand-directed catalysis to guide reactions. This project aims to combine the strengths of both concepts by incorporating functional groups from ligand-directed catalysis into ILs. The resulting ultrathin, self-healing, and durable IL films will direct catalytic reactions on active surfaces. The proposed project will investigate this novel concept using a rigorous surface science approach under ultrahigh vacuum conditions. Scanning probe microscopy will be employed to examine the local structure of active sites, while in-situ IR spectroscopy and molecular beam techniques will provide insights into adsorption geometries, reaction intermediates, and elementary kinetics. We will start with Pd single-crystal surfaces and later transition to atomically defined Pd model catalysts. Ultraclean films of functionalized ILs will be deposited onto these surfaces through physical vapor deposition. The focus will be on carbonyl- and cyano-functionalized imidazolium-based ILs, as these functional groups are known to exert significant effects in ligand-directed catalysis. Selective hydrogenation of carbonyl compounds (propanal, acrolein, acetophenone), a reaction of high practical importance, will be studied on IL-modified surfaces. This reaction can be influenced by co-adsorbed ligands, making it an ideal test case. The project will proceed in three phases: First, the interactions between ILs and surfaces will be scrutinized, with the goal of controlling the positioning of reaction-directing functional groups within the IL wetting layer. Second, the interactions between the functionalized ILs and reactants will be examined to identify interaction mechanisms, reaction intermediates, and IL-induced changes in activity and selectivity. Finally, the study will transition from single crystals to complex model catalysts to explore the role of particle-specific sites. The project is embedded within established collaborations that will provide tailor-made ILs, simulate ligand-directed SCILLs, and evaluate these systems in catalytic reactors. The ultimate objective is to uncover the fundamental surface chemistry of ligand-directed SCILLs and establish a knowledge base for future materials development.

• DFG Programme: Research Grants