The high potential of performing heterogeneous catalysis in confined mesoporous media within a supported ionic liquid phase (SILP) is studied using all-atom Molecular Dynamics (MD) simulations. Specifically, we investigate the possibility of immobilizing organometallic catalysts in confined media in a biphasic solution consisting of an ionic liquid (IL) and heptane as second phase. The confined medium is made of a pore with a diameter of about 5 nm. Divalent cationic Ru-alkylidene -<i>N</i>-heterocyclic carbene catalysts are placed in the IL. We were able to monitor the immobilization of the catalysts within the IL opening up the route for achieving higher turnover rates in the respective catalytic reactions. We further analyze the accumulation and diffusion of all molecular species within the pore environment, the influence of steric and IL-specific effects, the structuring of a varying solvent environment, and their synergistic interactions with the catalytic molecules. The calculation of the free energies involved in the process reveals that the catalytic reaction between reactants and catalysts must occur at the interface between the diffusive heptane and the IL, while the IL is preferentially layered close to the pore wall controlling the biphasic interface. Our investigations are supported by experimental evidence and provide a deeper understanding on the inherent details that control a rational design of a linker-free catalyst immobilization in nanometer-sized templates for catalytic applications.

Free energy considerations in confined heterocatalysis in a supported ionic liquid phase

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