Cooperative Photoredox Catalysis Under Confinement.

Photoredox catalysis has emerged as a potent means to conduct synthetic chemistry. Leveraging light to achieve challenging organic transformations has led to many developments, both of fundamental and industrial nature. Despite their potency, photoredox processes are inherently diffusion controlled, which can limit their ability to enable both reactivity and selectivity. Relevant to this is the idea of colocalizing cocatalysts in architectures that enable spatial proximity, promoting 'catalysis under confinement.' In this Concept review, we summarize recent designs and advancements using well-defined heterogeneous and homogeneous frameworks that enable dual photoredox catalysis, such as metal-organic frameworks, heterogeneous organic polymeric systems, and single-chain polymer nanoparticles (SCNPs). These advances generally stem from the material's inherent ability to enforce catalyst communication, typically resulting in expedient radical, electron, or energy transfer that accelerates reactivity. Whereas heterogeneous systems are comprehensively investigated, the design space arising from the modularity and versatility of a SCNP is quite large making the recyclable platform an intriguing candidate to investigate for confinement-enabled photoredox catalysis. We expect that both heterogeneous and homogeneous platforms systems detailed herein will continue to exhibit superior performance, while underscoring the importance of confinement to tackle diffusion-limited reactions.