BACKGROUND Nitrogen-doped titanium dioxide (TiO2) photocatalyst was synthesized successfully by a low temperature microwave-assisted sol-gel method. Ethylenediamine was used as a source of nitrogen dopants to extend and improve the photoresponse of the materials to visible light. The photocatalysts were characterized by several techniques to determine the structural, textural and optical characteristics. The activity of the materials was tested in the photoreduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) under visible light. RESULTS The results indicate that nitrogen ions were substitutedly doped into oxygen sites of the TiO2 lattice, resulting in band gap narrowing, which significantly promotes the visible light absorption of TiEN catalysts. When initial ethylenediamine concentration was increased, the content of nitrogen dopant and optical absorption in the visible region increased. Moreover, it was found that TiEN photocatalyst significantly enhances the photoreduction of 4-NP in comparison to the bare TiO2. CONCLUSION The increased photocatalytic activity of TiEN new materials are predominantly related to a lower energy gap, enhanced visible light absorption, higher reactive surface area and improved charge separation of photoinduced electron-hole pairs. (c) 2020 Society of Chemical Industry