Molecular doping of conjugated carbon nitride (CN) with pi-deficient pyridine ring was applied for the modification of CN photocatalysts. According to the density functional theory (DFT) calculations, the incorporation of it-deficient pyridine ring entities in the conjugated CN matrix can effectively modulate the intrinsic electronic and band structure of CN by relocating its pi-electrons. And then, a series of pyridine-doped CN photocatalysts were synthesized via thermal copolymerizing dicyandiamide (DCDA) with 2, 6-diaminopyridine (DPY). Integrating pi-deficient pyridine ring into the CN network by modification with DPY does not alter the crystal structures or the core chemical skeleton of CN. A significant alteration in the texture and morphology was also observed for the modified CN samples. Moreover, integrating it-deficient pyridine ring into the conjugated.CN network can actually engineer the electronic structure with tunable band-gap and promotes the migration and separation of photo-generating electron-hole pairs, which are in well agreement with the theoretical calculation results. The combined benefits of the molecular doping in terms of electronic, optical, surface and texture properties lead to a significant improvement in the photocatalytic activity for methyl orange (MO) degradation under visible light irradiation. The O-2 center dot-/center dot OOH radical is the major oxidation species in the photocatalytic oxidation process. The modulated CN incorporating pi-deficient aromatic systems possess a higher reduction potential because the extension of optical absorption of CN mostly results from the up-shift of HOMO, which is favorable for the photocatalytic degradation of organic pollutant. (C) 2015 Elsevier B.V. All rights reserved.