Cyano groups have been successfully introduced on the backbone edge of g-C3N4 to fabricate nitrogen defects under mild conditions, which are derived from incomplete polymerization of g-C3N4 after BaCO3 utilization. Characterization results indicate that the interfacial interaction between BaCO3 and carbon nitride is playing a significant role for introducing cyano groups into g-C3N4. Cyano groups working as electron capture centers are proved to change the band gap of carbon nitride, reducing the recombination rate of electron-hole pairs and promoting charge separation. As expected, the hydrogen evolution rate of nitrogen-defect-modified carbon nitride is improved to 71.57 mu mol h(-1), which is 13.5 times that of pristine C3N4. Meanwhile, the degradation efficiency of methyl orange is promoted (5 times that of pristine C3N4). This work is the first report on the fabrication of cyano-group-modified carbon nitride with BaCO3 utilization, and opens a new door for further exploring environmental-friendly carbon nitrides on energy conversion. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.