A convenient microwave treatment for synthesizing graphitic carbon nitride (g-C3N4) with outstanding nitrogen photofixation ability under visible light is reported. X-ray diffraction (XRD), N-2 adsorption, UV-vis spectroscopy, SEM, N2-TPD, EPR, photoluminescence (PL) and photocurrent measurements were used to characterize the prepared catalysts. The results indicate that microwave treatment can form many irregular pores in as-prepared g-C3N4, which causes the increased surface area and separation rate of electrons and holes. More importantly, microwave treatment causes the formation of many nitrogen vacancies in as-prepared g-C3N4. These nitrogen vacancies not only serve as active sites to adsorb and activate N-2 molecules but also promote interfacial charge transfer from catalysts to N-2 molecules, thus significantly improving the nitrogen photofixation ability. Moreover, the present process is a convenient method for large-scale production of g-C3N4 which is significantly important for the practical application. (C) 2016 Elsevier B.V. All rights reserved.