Light-Driven sp³-sp³ Cross-Coupling of Carboxylic Acids and Alkyl Halides over a Ni Single-Atom Catalyst

The coupling of two <i>sp³</i> hybridized fragments remains a challenging protocol for organic synthesis. Although visible light-driven metallaphotoredox catalysis, a method that combines photoabsorbers and transition metals, has become a powerful tool to conduct such transformations, resource economical and scalability issues persist, due to the use of catalysts and light absorbers which exploit critical raw materials (e.g., iridium complexes) and are homogeneous in nature. Here we report the first synergistic merger of metallic single-atom and photoredox catalysis, in the form of a Ni atom-supported carbon nitride material, for decarboxylative <i>sp³-sp³</i> cross-coupling between carboxylic acids and alkyl halides. This operationally straightforward system, comprised of only earth abundant components, works with chloro-, bromo-, and iodoalkanes, and exhibits a wide functional group tolerance in terms of both the coupling partners, <i>i.e</i>. the alkyl halide and carboxylic acid. Further still, since the metal and photoredox catalytic cycles were essentially combined within one single-atom material, we were able to easily recover and re-use the heterogeneous system for several times, preserving its activity between individual trials. With the help of computational studies, we have elucidated the active site of the Ni single-atom material, analyzing both the metal coordination with the carbon nitride support and binding of the substrates to the active site, thus proposing a plausible reaction mechanism. The reaction time is 83% shorter than the reported homogeneous procedure, making the method highly attractive for industrial applications. We thus further exemplify the versatility of our system through the synthesis of an API precursor, and the adaptation of our single-atom catalytic system within a continuous flow photoreactor device.