Cindy-Ly Tavera-Méndez

Heterogenized molecular catalysts commonly rely on covalent grafting to solid supports. Cleavage of these linkages under catalytic conditions, however, can compromise structural definition and control at the interface. Here, we introduce a ligand‐encoded anchoring strategy in which a platinum(II) bis(NHC) complex is immobilized on mesoporous silica (SBA‐15) exclusively through directional, non‐covalent F–Si interactions. The molecular pre‐catalyst trans ‐[Pt(L ^F ) ₂ Cl ₂ ] was structurally characterized by single‐crystal X‐ray diffraction and multinuclear solution‐state NMR spectroscopy. Advanced solid‐state MAS NMR experiments, including ¹⁹ F{ ²⁹ Si} REDOR, combined with molecular dynamics simulations, establish well‐defined F–Si contacts with internuclear distances on the Å‐scale and reveal the organization of the pre‐catalyst at the silica interface. A model hydrosilylation reaction demonstrates catalytic activity and retention of the molecular species on the support during turnover. This work establishes non‐covalent interface engineering as a viable strategy for structurally defined heterogenized catalysis.

To achieve high catalytic activity of artificial photosystems in carbon dioxide reduction or water reduction/oxidation into renewable energy vectors, the use of sacrificial electron do-nors (SEDs) remains mandatory. Despite significant progress in artificial photocatalysis, a detailed understanding of the influence of the SEDs on the reaction mechanism is still lack-ing. We have explored the roles of triethanolamine as SED in the selective CO2 to formic acid photoreduction promoted by various pentamethylcyclopentadienyl rhodium(III)-based porous materials as model catalysts, including polyoxometalate-doped systems. In the pres-ence of anionic polyoxometalates, agglomeration of protonated triethanolamine close to the catalytically active site favours H2 evolution over CO2 reduction, which can be modulated through the degree of confinement imposed by the pores size. Radical trapping experiments and EPR spectroscopy show that triethanolamine-radicals are crucial for a high activity in CO2 reduction. Triethanolamine-radicals act as electron relays in the efficient two-electron activation of the catalyst, regardless whether a homogeneous or a heterogeneous catalyst is used. In contrast, triethylamine-radicals cause deactivation of the one-electron reduced cata-lyst, thus highlighting the effect of different SED-intermediates and underling the im-portance of an appropriate SED.

Separation and reuse of the catalytically active metal complexes are persistent issues in homogeneous catalysis. Supported Ionic Liquid Phase (SILP) catalysts, where the catalytic center is dissolved in a thin film of a stable ionic liquid, deposited on a solid support, present a promising alternative. However, the dissolution of the metal center in the film leaves little control over its position and its activity. We present here four novel, task‐specific ionic liquids [FPh_nIm^HR]I (n=1, 2; R=PEG₂, C₁₂H₂₅), designed to self‐assemble on a silica surface without any covalent bonding and offering a metal binding site in a controlled distance to the support. Advanced multinuclear solid‐state NMR spectroscopic techniques under Magic Angle Spinning, complemented by molecular dynamics (MD) simulations, allow us to determine their molecular conformation when deposited inside SBA‐15 as a model silica support. We provide here conceptual proof for a rational design of ionic liquids self‐assembling into thin films, opening an avenue for a second, improved generation of SILP catalysts.