ABSTRACT Dual‐atom catalysts (DACs) provide great potential for boosted photoreduction of diluted CO 2 , while the significance of inert sites in DACs is still overlooked. Herein, by loading extra Zn atoms into conducive metal‐organic frameworks (CMOFs), we elaborately construct a well‐defined DACs with a NiZn─O 4 configuration to decipher the critical role of inert Zn sites in DACs. Under visible light irradiation in pure CO 2 , the NiZn─O 4 DACs with the optimal Zn/Ni ratio exert a boosted CO generation rate of 20.17 µmol h −1 with a selectivity of 97%, which is significantly higher than that of the pristine Ni─O 4 single atom catalysts (SACs) and most documented systems. Additionally, in diluted CO 2 , the activity difference between them increases, and the CO selectivity of Ni─O 4 SACs drops from 95% to 88%, while it remains nearly constant (94%) in the NiZn─O 4 DAC‐based system. Experiments combined with theoretical analysis demonstrate that the inert Zn sites enhance the electronic density of the coupled Ni sites, which accelerates electron transfer, promotes reduction kinetics, and lowers the energy barrier for the generation of * COOH key intermediate. This work highlights the intrinsic role of inert sites, paving new avenues for designing effective DACs for various applications.