Effectively controlling the selective conversion of CO 2 photoreduction to C 2 products presents a significant challenge. Here, we develop a heterojunction photocatalyst by controllably implanting Au nanoparticles and single atoms into unsaturated Mo atoms of edge-rich MoS 2 , denoted as Au n /Au 1 -CMS. Photoreduction of CO 2 results in the production of CH 3 COOH with a selectivity of 86.4%, which represents a 6.4-fold increase compared to samples lacking single atoms, and the overall selectivity for C 2 products is 95.1%. Furthermore, the yield of CH 3 COOH is 22.4 times higher compared to samples containing single atoms and without nanoparticles. Optical experiments demonstrate that the single atoms domains can effectively capture photoexcited electrons by the Au nanoparticles, or the local electric field generated by the nanoparticles promotes the transfer of photogenerated electrons in MoS 2 to Au single atoms, prolonging the relaxation time of photogenerated electrons. Mechanistic investigations reveal that the orbital coupling of Au5d and Mo4d strengthens the oxygen affinity of Mo and carbon affinity of Au. The hybridized orbitals reduce energy splitting levels of CO molecular orbitals, aiding C-C coupling. Moreover, the Mo-Au dual-site stabilize the crucial oxygen-associated intermediate *CH 2 CO, thereby enhancing the selectivity towards CH 3 COOH. The cross-scale heterojunctions provide an effective strategy to simultaneously address the kinetical and thermodynamical limitations of CO 2 -to-CH 3 COOH conversion.