Polymeric graphitic carbon nitride is an efficient visible-light photocatalyst for NO removal which can be prepared by precursors rich in C and N elements, such as melamine, dicyandiamide, urea, and thiourea et al. The method of synthesizing carbon nitride from melamine and dicyandiamide has much higher yield and, whereas the photocatalytic efficiency of the product was lower than that of synthesizing from urea and thiourea. In present work, the photocatalytic performance of carbon nitride prepared from dicyandiamide was significantly improved; melem/g-C3N4 was prepared from dicyandiamide under lower temperature with superior performance on NO purification than pure carbon nitride (g-C3N4). Suitable depolymerization ratio and surface protonation status could bring about higher photocatalytic activity through XPS characterizations. Through the SEM images, two kinds of morphology nanorod carbon nitride and bulk carbon nitride cross each other together and the ratio variation are consistent with reaction temperature and time. The different band gap structure between g-C3N4 and melem could drive the photogenerated electron-hole separation due to the offsets and lead to higher NO removal efficiency. This heterojunction cdnsisted of melem and g-C3N4 was developed here just by adjusting reaction temperature and time, which could open up a new possibility for air purification in a low cost way. (C) 2016 Elsevier B.V. All rights reserved.