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

A strategy to improve homogeneous molecular catalyst stability, efficiency, and selectivity is immobilization on supporting surfaces or within host matrices. Here, we examine the immobilization of CO2 reduction catalyst [ReBr(CO)3(4,4'-dcbpy)] and 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 centre and photosensitizer, and consequently the apparent catalytic rates. These results allow for a rational understanding of optimized supramolecular layout of catalyst, photosensitizer, and host matrix.