Seeking low-cost and efficient method to convert nitrogen into ammonia under mild conditions is of great significance to modern agriculture and industry. Herein, a novel bioinspired polymer photocatalyst, polythiocyanuric acid ((C 3 N 3 S 3) n) constructed by s -triazines bridged by disulfide bonds, the pivotal light-capturing component in the natural algae, is synthesized, whereby the s -triazine units serve as electron acceptor, and the disulfide bridges deliver strong electron transport capacity, and thus such a sulfur-rich polymer can not only effectively harvest sunlight, but also deliver efficient photogenerated charge transport. Consequently, the resultant (C 3 N 3 S 3) n displays highly efficient N 2 photofixation activity under UV-Vis or visible light illumination. With the aid of Au nanoparticles, the polymer achieves a UV-Vis-light-driven NH 3 yield up to 366 μmol h−1 g−1 with an ultrahigh apparent quantum efficiency (14.6%) at 420 nm. The present results provide important guidance for the development of stable and efficient bioinspired polymer photocatalysts for artificial N 2 fixation under mild conditions. [Display omitted] • (C 3 N 3 S 3) n polymer with disulfide bridged-triazine rings is prepared via one-pot method. • The resultant polymer is used as metal-free bioinspired photocatalyst for N 2 fixation. • s -Triazine rings in polymer act as electron acceptor and disulfide bond as transport unit. • The NH 3 yield is significantly improved with the aid of Au nanoparticles as cocatalyst. [ABSTRACT FROM AUTHOR]