Mesoporous structured carbon/bismuth oxide (mCBiO) composites were successfully fabricated through a facile and green process through CO2 mediated approach, which provided a unique medium without the need of any precipitant and mesoscaled organic template. For the photodegradation of RhB and phenol, the photocatalyst synthesized by CO2 mediated approach exhibited excellent recycling stability and enhanced photodegradation rate compared with the pure Bi2O3 and the reference sample synthesized in pure ethanol. Additionally, the possible mechanism of visible-light activity over mCBiO composites was proposed. This work developed a simple, green and economic route for, the fabrication of mesoporous structured C-based metal oxide composites without the necessary of mesoporous template and precipitant. (C) 2015 Elsevier B.V. All rights reserved.