The development of new kinds of organic semiconductor-based photocatalysts has being attracting more and more research attentions due to their advantages over traditional inorganic photocatalysts and their great application prospects. In this work, polyacrylonitrile (PAN), a low-cost homopolymer largely used in the textile industry, was found for the first time to possess the photocatalytic capability due to its good light absorption and proper electronic band structure to generate radicals. Under simulated solar illumination, it successfully degraded organic pollutants of phenol and sulfamethoxazole (SMX), and disinfected Escherichia coli (E. coli) bacteria. After 2 h treatment, the residual concentrations of phenol and SMX decreased to ∼ 75.9 % and ∼ 89 % respectively, while the survival ratio of E. coli cells dropped to only ∼ 28 % after 1 h treatment. h+ and ·O2– were found to be the main active species in its photocatalytic process. It had a good stability and reusability, and worked well in the real water matrix of tap water, beneficial for its practical applications. PAN, PAN-based organics, and organics with similar structures as PAN could become a new series of organic semiconductor-based photocatalysts for various technical applications, especially as wearable products with self-disinfection property to provide protection against bacteria and viruses.