In this study, new organic-inorganic g-C₃N₄/CoAl-LDH nanocomposites were prepared and introduced to fabricate photocatalytic cement mortars by internal mixing, coating, and spraying. The photocatalytic depollution of both g-C₃N₄/CoAl-LDH and cement mortars was assessed by NO_x degradation reaction under UV-visible light irradiation. The study results suggested that the degradation efficiency of g-C₃N₄/CoAl-LDH nanocomposites improved with an increase in g-C₃N₄ content. The g-C₃N₄/CoAl-LDH_1.5 nanocomposite displayed the highest NO_x degradation capacity, which was about 1.23 and 3.21 times that of pure g-C₃N₄ and CoAl-LDH, respectively. The photocatalytic cement mortars which were all fabricated using different approaches could effectively degrade the target pollutants and exhibited significant compatibility between g-C₃N₄/CoAl-LDH and cementitious substrate. Among them, the coated mortars showed strong resistance to laboratory-simulated wearing and abrasion with a small decrease in degradation rate.