A simple structural design principle of poly(arylene ethynylene) pi-conjugated microcellular polymers as the pure organic, heterogeneous photocatalytic systems is presented. They are synthesized by the Sonogashira cross-coupling polymerization of 1,3,5-triethynylbenzene and 1,4-diiodobenzene, 2,5-dimethoxy-1,4-diiodobenzene or 2,6-diiodo-4-nitrophenol within the high internal phase emulsion (HIPE). Such poly(arylene ethynylene)-based polyHIPEs allow for fine alignment of the valence and conduction band levels to enhance their photocatalytic activity. The resulting polyHIPEs exhibit substantial semiconducting properties, such as strong light-harvesting capability in the visible-light region, most likely due to their pi-extended poly(arylene ethynylene) main backbone with donor-acceptor characters having optical fine-tuned bandgaps over a range of 1.70-2.35 eV. The intriguing properties allow these polyHIPE photocatalysts to efficiently catalyze the degradation of water-dissolved endocrine disrupting compound bisphenol A (BPA) under visible light.