Novel porous β-Bi2O3/Bi2O2CO3 p-n heterostructures were synthesized by partially decomposing porous Bi2O2CO3 at 300-375 °C. The structures, morphologies, optical properties, and specific surface areas of the as-synthesized samples were characterized by means of thermogravimetry and differential scanning calorimetry, X-ray diffraction, scanning electron microscopy, UV-Vis spectroscopy, and N2 gas adsorption. Two types of dyes, methyl orange (MO) and methylene blue (MB), were chosen as model organic pollutants to evaluate the photocatalytic activity of the as-synthesized samples. The porous β-Bi2O3/Bi2O2CO3 p-n heterostructures exhibited much higher photocatalytic activity than β-Bi2O3 and Bi2O2CO3 and MO and MB could be completely degraded within 24 and 50 min, respectively. In addition, phenol as a colorless organic pollutant was also chosen to further study the photocatalytic activity of Bi2O2CO3, β-Bi2O3 and β-Bi2O3/Bi2O2CO3. The β-Bi2O3/Bi2O2CO3 heterostructures also showed much higher photocatalytic activity for the photodegradation of phenol than β-Bi2O3 and Bi2O2CO3. The obtained results indicated that the formed p-n heterojunction in the porous β-Bi2O3/Bi2O2CO3 composite significantly contributed to the improvement of electron-hole separation and the enhancement of photocatalytic activity. The mechanisms for the enhanced photodegradation of selected organic pollutants over the β-Bi2O3/Bi2O2CO3 composite are discussed in this study.