Photocatalytic oxidation is a technology developed in recent years for the degradation of indoor air pollutants. In this study, magnesium cement-based photocatalytic material (MPM) was prepared by loading TiO₂ photocatalysts onto a SiO₂-modified basic magnesium chloride whisker (BMCW) surface, and was subsequently sprayed evenly on the surface of putty powder to form a photocatalytic functional wall coating (PFWC) material. Then, by introducing Ag, visible light photocatalytic functional wall coating (VPFWC) materials were also prepared. The results show that TiO₂ and SiO₂ form Ti–O–Si bonds on the BMCW surface, and the PFWC presents a promising degradation effect, with a photocatalytic removal rate of 46% for gaseous toluene, under ultraviolet light for 3 h, and an MPM coating concentration of 439 g/m². This is related to the surface structure of the functional coating, which is formed using putty powder and MPM. The visible light photocatalytic efficiency of the VPFWC increased as the spraying amount of the AgNO₃ solution increased, up to 16.62 g/m², and then decreased with further increasing. The gaseous toluene was degraded by 28% and 73% in 3 h, by the VPFWC, under visible light and ultraviolet light irradiation, respectively. In addition, the photocatalytic performance of the PFWC/VPFWC also showed excellent durability after being reused five times.