Host-Guest Interactions in a Metal-Organic Framework Isoreticular Series for Molecular Photocatalytic CO₂ Reduction

A strategy to improve homogeneous molecular catalyst stability, efficiency, and selectivity is the immobilization on supporting surfaces or within host matrices. Herein, we examine the co-immobilization of a CO₂ reduction catalyst [ReBr(CO)₃ (4,4'-dcbpy)] and a photosensitizer [Ru(bpy)₂ (5,5'-dcbpy)]Cl₂ using the isoreticular series of metal-organic frameworks (MOFs) UiO-66, -67, and -68. Specific host pore size choice enables distinct catalyst and photosensitizer spatial location-either at the outer MOF particle surface or inside the MOF cavities-affecting catalyst stability, electronic communication between reaction center and photosensitizer, and consequently the apparent catalytic rates. These results allow for a rational understanding of an optimized supramolecular layout of catalyst, photosensitizer, and host matrix.