Tailoring Secondary Coordination Sphere Effects in Single-metal-site Catalysts by Surface Immobilization of Supramolecular Cages.

Controlling the coordination sphere of heterogeneous single-metal-site catalysts is a powerful strategy for fine-tuning their catalytic properties but is fairly difficult to achieve. To address this problem, we immobilized supramolecular cages where the primary- and secondary coordination sphere are controlled by ligand design. The kinetics of these catalysts were studied in a model reaction, the hydrolysis of ammonia borane, over a temperature range using fast and precise online measurements generating high-precision Arrhenius plots. The results show how catalytic properties can be enhanced by placing a well-defined reaction pocket around the active site. Our fine-tuning yielded a catalyst with such performance that the reaction kinetics are diffusion-controlled rather than chemically controlled.