Crystal defects of semiconductor materials exert huge impact on their physical and chemical properties. Herein, we report the development of oxygen vacancy (OV) concentration-tunable Bi2O2CO3 (BOC) via a facile and scalable precipitation approach with assistance of glyoxal as reductant at atmospheric environment. Introduction of OV takes a triple-functional role in regulating the band structure and charge movement behaviors of BOC. It not only renders appearance of defect band level in the forbidden band, allowing BOC drastically extended photoabsorption from 360 to 520 am, but also tremendously promotes the charge carrier density, bulk charge separation, surface charge separation and interfacial charge transfer. In contrast to pristine BOC, OV-BOC demonstrates highly promoted photocatalytic performance for water splitting into H-2 evolution, NO removal from the gas phase and degradation of a typical antibiotic tetracycline hydrochloride, where the H-2 production is first reported for BOC. Additionally, the OV concentration of BOC can be continuously modulated only by regulating the concentration of glyoxal, thereby achieving the adjustable photoabsorption and band structure. Our work enables smart design on oxygen vacancy-activated photocatalytic materials for solar-energy-conversion applications through a readily achievable tactic.