We found that various layered double hydroxides (LDHs) showed good activity for the photocatalytic conversion of CO2 in an aqueous solution. Isotope experiments using (CO2)-C-13 as a substrate clearly revealed that CO was generated as a main reduction product of CO2. Ni-Al LDH (Ni/Al = 4) exhibited the largest amount of CO evolved among the various kinds of LDHs. Especially, Ni-Al LDHs fabricated from chlorides showed the higher conversion of CO2 to CO than those from nitrates. The amount of CO evolved was increased by the addition of chloride ions into the reaction solution, on the other hand, the addition of carbonate and hydrocarbonate ions did not enhance the conversion of CO2 but promoted the selectivity to H-2 evolution for water splitting. (C) 2014 Elsevier B.V. All rights reserved.