Nitrogen-enriched hierarchical porous carbon nanofibers (NHCFs) are promising candidates for supercapacitors. However, the synthesis of these carbons with high N content and large specific surface area is still great challenging. Here, a flexible NHCF paper is fabricated by electrospinning zeolitic imidazolate framework-8 (ZIF-8) suspended in polyacrylonitrile (PAN) solution, followed by a combined heating and acid treatment. The specific surface area and N content of the prepared NHCFs can be controlled by varying the amounts of ZIF-8 and calcination temperature. The highest specific surface area (559 m(2) g (1)), ultrahigh N content (15.59 wt%) and best electrochemical performance can be obtained from the calcination of PAN/ZIF-8 (66.7 wt%) at 800 degrees C, with a maximum specific capacitance of 302 Fg (1) at a current density of 0.5 Ag (1). In addition, the specific capacitance up to 146.7 Fg (1) can still be obtained at high current density of 40 Ag (1). The excellent electrochemical performance can be attributed to the synergetic effect of high nitrogen content, hierarchical porous structure and high specific surface area. (C) 2017 Published by Elsevier Ltd.