AbstractBACKGROUNDPhotocatalytic water treatment by using semiconductor material with low‐cost, along with green and environmental features, is the main candidate for the actual application of photocatalytic reactions.RESULTSThe ternary CoO/g‐C3N4/Co3O4 nanocomposite with p‐n‐p type heterojunction was fabricated through a one‐step solvothermal method follow‐up water washing process. The as‐prepared CoO/g‐C3N4/Co3O4 nanocomposite photocatalyst exhibited high visible‐light photocatalytic efficiency (92% within 80 min) during the degradation of tetracycline (TC). The degradation rate constant of CoO/g‐C3N4/Co3O4 nanocomposite is 0.025 min−1, which is 8.3, 4.3 and 2.3 times higher than that of single CoO, g‐C3N4 and binary CoO/g‐C3N4, respectively.CONCLUSIONA series of characterization experiments further confirmed that the photocatalytic performance of the synthesized CoO/g‐C3N4/Co3O4 composite materials was improved due to the following two points: (i) improved separation and migration ability of photo‐induced electron–hole pairs, and (ii) enhanced visible light absorption range. © 2021 Society of Chemical Industry (SCI).