Photocatalytic CO₂ reduction to valuable chemicals, especially fuels, is considered as a promising strategy to mitigate CO₂ accumulation and tackle the energy crisis, among which photocatalysis is vital to achieve efficient and selective reduction of CO₂. In this work, phosphorus-doped hollow polygonal g-C₃N₄ rods were prepared through phosphoric acid assisted self-assembly under hydrothermal conditions and subsequent thermal polymerization using phosphoric acid as the phosphorus source and melamine as the nitrogen-rich precursor. The resulting phosphorus-doped hollow polygonal g-C₃N₄ rods feature increased specific surface area, visible light absorption and photogenerated carrier separation and transfer efficiency according to the structure and photoelectric properties characterization. Coupled with an earth abundant metal-based complex, i.e. [Co(bpy)₃]Cl₂, as a co-catalyst, the phosphorus-doped hollow polygonal g-C₃N₄ rods deliver a CO evolution rate of up to 447.5 μmol g⁻¹ h⁻¹ with a selectivity of ca. 96%, being much higher compared to the pristine g-C₃N₄ (67.01 μmol g⁻¹ h⁻¹ with a selectivity of ca. 94%) resulting from the improved light harvesting and charge transfer to the co-catalyst. Remarkably, the phosphorus-doped hollow polygonal g-C₃N₄ rods can be reused 6 times while retaining constant catalytic activity in the photoreduction reaction. This work presents new insights into photocatalytic CO₂ reduction by developing non-metal doping and hollow structural designs for semiconductor photocatalysts.