Facile synthesis of β-Bi2O3/Bi2O2CO3 nanocomposite with high visible-light photocatalytic activity

•β-Bi2O3/Bi2O2CO3 composites were synthesized for the first time.•β-Bi2O3/Bi2O2CO3 composites were obtained via suitable calcination of Bi2O2CO3 precursor.•β-Bi2O3/Bi2O2CO3 composites showed greatly reduced energy band gaps.•Composite obtained at 400 °C exhibited the highest photocatalytic activity.

β-Bi2O3/Bi2O2CO3 composite nanosheets are synthesized via a rational heat-treatment of Bi2O2CO3 precursor. The precursor transforms to β-Bi2O3/Bi2O2CO3 composites and α-Bi2O3 phase under different calcination conditions. The photocatalytic activities are evaluated and compared through the photodegradation of methylene blue (MB) under visible-light irradiation. β-Bi2O3/Bi2O2CO3 composites exhibit much higher photodegradation activity than Bi2O2CO3 and α-Bi2O3 products. The significant enhancement is attributed to the formation of β-Bi2O3/Bi2O2CO3 heterojunctions, which is favorable for the low recombination rate of the electron–hole pairs.