Conjugation Engineering Boosts Alkynyl‐Copper Photocatalysis for Efficient Selective Aerobic Oxidation

Abstract Phenylacetylide‐copper (PACu), as an important photoactive intermediate in copper‐catalyzed cross‐couplings, suffers from limited visible‐light absorption, rapid radiative recombination, and poor photostability, hindering its practical application. Herein, we report a conjugation engineering strategy to address these challenges by replacing phenylacetylene with extended π‐system ligands, such as 2‐ethynylnaphthalene (NA), 9‐ethynylphenanthrene (FA), and 1‐ethynylpyrene (BA), yielding a series of new alkynyl‐copper photocatalysts (NACu, FACu, BACu). Experimental and theoretical studies reveal that enhanced π‐conjugation narrows the band gap to 1.95 eV (BACu), extends absorption beyond 600 nm, promotes charge separation, and suppresses Cu I oxidation during photocatalysis. The optimized BACu demonstrates exceptional photocatalytic activity and stability in [4 + 2] cycloaddition, Glaser coupling, and benzylamine oxidation, achieving >99% conversion and selectivity with excellent recyclability. This work provides fundamental insights into electronic structure modulation via conjugation engineering, offering a universal strategy for designing efficient and stable metal‐alkynyl photocatalysts.