Switchable, organic microporous networks were synthesized by Sonogashira coupling of tetrabromophenolphthalein with 1,4-diethynylenebenzene using optimized reaction conditions. The resulting networks are microporous and have specific surface areas exceeding 800 m(2) g(-1). The microporosity and the pore polarity are sensitive to the pH value as evidenced by nitrogen and carbon dioxide physisorption experiments. The switching between the open and closed form of the lactone ring is reversible, but some porosity is lost throughout the process. The colored, alkaline salts of these networks are photochemically active, as shown by the effective heterogeneous photosensitization of the photopolymerization of methyl methacrylate with visible light.