Programmable Photocatalytic Activity of Multicomponent Covalent Organic Frameworks Used as Metallaphotocatalysts

The multicomponent approach allows to incorporate several functionalities into a single covalent organic framework (COF) and consequently allows the construction of bifunctional materials for cooperative catalysis. The well‐defined structure of such multicomponent COFs is furthermore ideally suited for structure‐activity relationship studies. We report a series of multicomponent COFs that contain acridine‐ and 2,2’‐bipyridine linkers connected through 1,3,5‐benzenetrialdehyde derivatives. The acridine motif is responsible for broad light absorption, while the bipyridine unit enables complexation of nickel catalysts. These features enable the usage of the framework materials as catalysts for light‐mediated carbon−heteroatom cross‐couplings. Variation of the node units shows that the catalytic activity correlates to the keto‐enamine tautomer isomerism. This allows switching between high charge‐carrier mobility and persistent, localized charge‐separated species depending on the nodes, a tool to tailor the materials for specific reactions. Moreover, nickel‐loaded COFs are recyclable and catalyze cross‐couplings even using red light irradiation. Various multicomponent COFs bearing both a moiety for photosensitization and complexation of nickel catalysts were synthesized using reticulation with different 1,3,5‐triformylbenzene nodes. This enabled the switching between persistent, charge‐separated species or efficient charge‐carrier mobility for different metallaphotocatalytic cross‐coupling reactions based on the node unit. The frameworks showed recyclability and the possibility to drive the reactions using red light irradiation.