We report an unique 2D/2D Iodine doped BiOIO3/g-C3N4 heterojunction was successfully prepared. The iodine doped BiOIO3 was prepared by a simple solvent exchange method and combined with g-C3N4 by solvothermal method. The prepared photocatalyst has potential application value in the future due to its excellent stable cycle property. BiOIO3 nanoplates and g-C3N4 nanosheets form a close interfacial contact directly, so the catalyst has higher charge transport efficiency and wide visible range due to the introduction of iodide ions. Synergistic heterojunction exhibits strong photocatalytic activity for degradation of NO at ppb-level under visible light, of which 30% Iodine doped BiOIO3/g-C3N4 can achieve a maximum removal rate of 57% for NO. According to the experimental results of ESR and other experiments, a more complex Z-scheme photocatalytic mechanism is proposed, which has stronger redox ability than the traditional mechanism. (C) 2020 Published by Elsevier Inc.