Single-Site Nickel on Photoactive sp ² Carbon-Conjugated COF for Synergistic Photocatalytic Organic Transformations

The precise construction of robust photoredox/organometallic platforms holds great potential for synergistic metallaphotocatalytic (MPC) organic transformations, yet it is highly challenging. Herein, we demonstrate a facile and versatile methodology of post-synthetic metallization (PSM) for precise immobilization of single-atom Ni sites into a photosensitive triazine-functionalized sp2 carbon-conjugated COF (TFPT-BpyDAN-COF) to construct a robust dual photoredox/Ni catalyst, TFPT-BpyDAN(Ni)-COF. TFPT-BpyDAN(Ni)-COF showcases efficient MPC C−S/C−N cross-coupling performance between various aryl iodides and amines/thiols with yields of up to 99%, which is better than its homogeneous counterpart, due to a spatial proximity effect of photoredox centers and Ni catalytic centers that effectively facilitates rapid electron transfer to produce NiI active sites for the oxidative addition. Moreover, TFPT-BpyDAN(Ni)-COF presents good recyclability and durability, attributable to its high physicochemical stability and distinct site isolation effect. The underlying MPC mechanism has been well illustrated by detailed experiments. This work demonstrates that immobilizing organometallic catalysts into a photoactive full-sp2 carbon-conjugated COF offers significant benefits for C−S/C−N bond formation, providing an effective strategy for ingeniously designing high-performance MPC scaffolds.