The three kinds of well-known bismuth molybdates alpha-Bi2Mo3O12, beta-Bi2Mo2O9, and gamma-Bi2MoO6 have been prepared employing mild hydrothermal methods. By tuning the Bi/Mo ratio and pH values, controlling formation of bismuth molybdates can be achieved. Low pH and high concentration of molybdenum lead to the formation of alpha-Bi2Mo3O12. High pH and high concentration of bismuth lead to the formation of gamma-Bi2MoO6. The pure form of the beta-phase can be prepared by calcining the hydrothermal product at 560 degrees C. Photophysical and photocatalytic studies show that Aurivillius structure gamma-Bi2MoO6 shows an intense absorption band in the visible light region and better photocatalytic activity than alpha-Bi2Mo3O12 and beta-Bi2Mo2O9 under visible light irradiation. The factors that result in different photocatalytic activities for three kinds of photocatalysts are discussed. (C) 2009 Elsevier B.V. All rights reserved.