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.

Syngas, a mixture of CO and H₂, is a high‐priority intermediate for producing several commodity chemicals, e.g., ammonia, methanol, and synthetic hydrocarbon fuels. Accordingly, parallel sunlight‐driven catalytic conversion of CO₂ and protons to syngas is a key step toward a sustainable energy cycle. State‐of‐the‐art catalytic systems and materials often fall short as application‐oriented concurrent CO and H₂ evolution requires challenging reaction conditions which can hamper stability, selectivity, and efficiency. Here a light‐harvesting metal‐organic framework hosting two molecular catalysts is engineered to yield colloidal, water‐stable, versatile nanoreactors for photocatalytic syngas generation with highly controllable product ratios. In‐depth fluorescence, X‐ray, and microscopic studies paired with kinetic analysis show that the host delivers energy efficiently to active sites, conceptually yielding nanozymes. This unlocked sustained CO₂ reduction and H₂ evolution with benchmark turnover numbers and record incident photon conversions up to 36%, showcasing a highly active and durable all‐in‐one material toward application in solar energy‐driven syngas generation.