<p>To address the issue of reduced photocatalytic efficiency caused by nanoparticle aggregation of TiO₂ in the coating system, which significantly compromises its degradation performance, we prepared Fe-TiO₂ inorganic coatings using calcined metakaolin as the primary base material and an alkali activator. By comparing the mechanical blending method and the in situ growth method, it was found that coatings prepared by the in situ growth method exhibited higher photocatalytic efficiency and better surface uniformity; the coating achieved a formaldehyde degradation efficiency of 87% over 7&#xa0;days in the self-made airtight glass chamber. Experiments showed that the optimal degradation effect was achieved when the photocatalyst content was 5%. Additionally, after four cycles of use, the degradation efficiency slightly decreased but remained stable. Basic performance tests of the coating indicated that its workability, film appearance, hardness, adhesion, water resistance, and alkali resistance all met standard requirements, demonstrating that the addition of the photocatalyst did not adversely affect the coating’s performance. Overall, the Fe-TiO₂ inorganic coating prepared by the in situ growth method exhibits high formaldehyde degradation efficiency and good stability, making it suitable for indoor air purification.</p> Graphical abstract <p></p>