An optofluidic photoreactor including an optical waveguide having an input, characterized by an evanescent optical field confined along an outer surface of the optical waveguide produced by radiation propagating in the optical waveguide, means for inputting light to the input of the optical waveguide, and a photoactive material disposed substantially only within the evanescent field. A method for optically activating a photoactive material in an optofluidic photoreactor to convert carbon dioxide and water into other molecules that may be useful as a fuel or a chemical feedstock.