N rich porous carbon based solid acids (NPC-[C_xN][X]) have been successfully synthesized by treatment of N rich porous carbon (NPC) with various quaternary ammoniation reagents such as iodomethane, 1,3-propane sultone, and 1,4-butanesultone, and ion exchange with various strong acids such as HSO₃CF₃, H₂SO₄, H₃PW₁₂O₄₀, HBF₄etc. The NPC support was synthesized by carbonization of KOH-activated polypyrrole without using additional templates. Various characterizations showed that NPC-[C_xN][X] possesses abundant nanopores, large Brunauer–Emmett–Teller surface areas, good stability, and strong and controllable acid sites with Brønsted characteristics. The immobilized acidic groups were homogeneously dispersed into NPC-[C_xN][X]. Notably, NPC-[C_xN][X] acted as efficient, reusable and generalized solid acids, which showed excellent activity in various acid-catalyzed reactions such as esterification and transesterification in the synthesis of biodiesel, dehydration of fructose into 5-hydroxymethylfurfural, depolymerization of crystalline cellulose into sugars, and condensation of phenol with acetone in the synthesis of bisphenol A, much higher than that of various solid acids such as Amberlyst 15, H-ZSM-5, H-USY, and sulfonic group functionalized ordered mesoporous silicas. The preparation of NPC-[C_xN][X] leads to the development of porous carbon based solid acids with controllable structural characteristics and excellent catalytic activity.