Manipulating t he sub-units of conjugated co-polymers was a convenient and promising strategy for developing novel functional materials. Here a soluble alternating copolymer (P-Boc) consisted of 9,9-dialkylfluorene and 1,4-diketo-2,5-di(t-butoxycarbonyl)-3,6-diphenyl-pyrrolo[3,4-c]-pyrrole was designed and synthesized. Heating the spin-coated P-Boc film could afford an insoluble polymer film (P-2H) with multiple lactam hydrogen units by the removal of the t-butoxycarbonyl groups. Unlike the small molecules with lactam hydrogen, the P-2H film was insoluble and exhibited the remarkable naked-eye visible color change and a new long-wavelength absorption band in the fluoride anion-containing organic solution. The naked-eye visible and spectroscopic detection limits for fluoride anion were similar to 10(-6) and -10(-8) M, respectively. Moreover, the fluoride anions bonded with P-2H film could be easily removed by immersing in acidic solutions, and the resulting P-2H film could again probe fluoride anion. Energy dispersive X-ray spectroscopy analysis indicated that most lactam units in P-2H film could bond fluoride anions and the bonded fluoride anions could be removed quantitatively. These results demonstrated that P-2H was not only an efficient and renewable fluoride anion chemosensor but also might become a promising fluoride anion extractor. (C) 2018 Elsevier Ltd. All rights reserved.