The CO
2 conversion to chemically valuable species is important in developing alternative fuels and various raw materials for different industries. It also aids in preventing the continuous rise in global temperature due to the green house effect of CO
2. In this paper a brief overview of the CO
2 chemical reduction is presented. Further, a gas-solid heterogeneous system (as shown in Figure 1) for solar-chemical energy conversion of CO
2-SCR (Selective Catalytic Reduction) with H
2O on various nanostructure photocatalysts is discussed, in which, the H
2O serves as hydrogen resource (or reducing agent) and CO
2 as carbon resource (or oxidant), UV/Visible light provides the reaction energy and the prorous semiconductor provides the active centers for such a photocatalysis process to ultilize the solar energy through chemical conversion or storage process. Last, various crystal phase (rutile or anatase) and size (2-20 nm) of low dementional nano-TiO
2 (particle, ribbon or tube) and Pt supported/composite photocatalysts are synthesized via the sol-gel and high temperature hydrothermal methods. The catalysts are characterized with powder X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), selected-area electron diffraction (SAED), photoluminescence and the photocatalytic reduction of CO
2 with H
2O to produce chemically valuable compound such as CH
4 or CH
3OH are among the most desirable and challenging goals.
