Photocatalytic carbon dioxide (CO₂) to carbon monoxide (CO) offers a promising way for both alleviating the greenhouse effect and meeting the industrial demand. Herein, we constructed a Co single-atom catalyst with intentional low-coordination environment design on porous ZnO (denoted as Co₁/ZnO). Impressively, Co₁/ZnO exhibited a remarkable activity with a CO yield rate of 22.25 mmol·g⁻¹·h⁻¹ and a selectivity of 80.2% for CO₂ photoreduction reactions under visible light. The incorporation of single Co atoms provided an additional photo-generated electron transfer channel, which suppressed the carrier recombination of photocatalysts. Moreover, the unsaturated Co active sites were capable to adsorb CO₂ molecule spontaneously, thus facilitating the activation of CO₂ molecule during CO₂ reduction course.