Abstract: A method for photo-oxidising an organic substrate to form an organic product is disclosed comprising: a) mixing oxygen, a supercritical fluid, a photocatalyst, a liquid fluorous solvent and an organic substrate to form a mixture; and b) irradiating the mixture to form an organic product. Also disclosed is a method for separating a photocatalyst from an organic product comprising the steps of: a) providing a mixture comprising a supercritical fluid; an organic product; a fluorous solvent; a photocatalyst; and optionally an organic substrate and optionally oxygen; wherein the organic product, fluorous solvent, photocatalyst and optional organic substrate and optional oxygen are dissolved in the supercritical fluid; and b) reducing the pressure of the mixture to a pressure below the critical pressure of the supercritical fluid in order to form a gaseous phase.