In conclusion, we have identied graphene oxide as an effective, low cost photocatalyst for simultaneous CO2 reduction and solar energy harvesting. Our studies show that by modulating the oxygenated functional groups, the methanol conversion rate can be achieved up to 0.172 mmol g cat1 h1 on graphene oxide (GO-3), under 300-Watt halogen lamp irradiation. These conversion rates are much higher than that of TiO2. We believe that our finding would be widely applicable to the graphene oxide based composites with metal or metal oxide nanoparticles to develop a cost effective technique for simultaneous solar energy harvesting and CO2 reduction.