This work reports a bi-functional activated porous carbon (PC) prepared from a biomass tofu, with excellent capacities for charge storage and adsorption of organic dyes, which is enabled by decorating with Fe3C/Fe3O4/C nanosheets. The in-situ growth and self-assembly of the nanosheets on the carbon surface are achieved by a one-step catalytic carbonization of tofu simultaneously with FeCl3 and ZnCl2 catalysts. Due to the high surface area and unique iron compounds-containing and sheet-like structures, the PCs exhibit an electrochemical capacitance of 315 F g(-1) at 0.5 A g(-1) as supercapacitor electrodes, and an ultrahigh adsorption capacity of 918 mg g(-1) for methylene blue (MB) and 868 mg g(-1) for Rhodamine B (RhB). This study provides a new perspective for understanding the effects of surface engineering on increasing charge storage and dye adsorption ability of biomass-derived PCs as well as for developing bi-functional PCs with novel magnetic properties.