“…There are several reviews on CO 2 photoreduction (Sutin et al, 1997;Song, 2006;Usubharatana et al, 2006;Kitano et al, 2007;Indrakanti et al, 2009;Morris et al, 2009;Dorner et al, 2010;Roy et al, 2010;Biswas et al, 2011;Windle and Perutz, 2012;Hong et al, 2013), covering both fundamental CO 2 photoreduction mechanisms and practical photocatalyst development. This article intends to provide a state-of-the-art overview of the basics of CO 2 photoreduction pathways, and a comparison of different CO 2 photoreduction systems as listed below: (1) Biological systems, including mainly algae; (2) Inorganic photocatalysts, mostly transition metal oxides (or semiconductors), in particular TiO 2 -based catalysts; (3) Organic photocatalysts, including mainly metalorganic complexes; and (4) inorganic and organic/biological hybrid, or the so-called biomimetic systems, consisting of enzyme-activated or dye-sensitized semiconductors.…”