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

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.