Replacing traditional polymer-based precursors with small molecules is a promising pathway toward facile and controllable preparation of porous carbons but remains a prohibitive challenge because of the high volatility of small molecules. Herein, a simple, general, and controllable method is reported to prepare porous carbons by converting small organic molecules into organic molecular salts followed by pyrolysis. The robust electrostatic force holding organic molecular salts together leads to negligible volatility and thus ensures the formation of carbons under high-temperature pyrolysis. Meanwhile, metal moieties in organic molecular salts can be evolved into in-situ templates or activators during pyrolysis to create nanopores. The modular nature of organic molecular salts allows easy control of the porosity and chemical doping of carbons at a molecular level. The sulfur-doped carbon prepared by the ionic solid strategy can serve as robust support to prepare small-sized intermetallic PtCo catalysts, which exhibit a high mass activity of 1.62 A·mg_Pt⁻¹ in catalyzing oxygen reduction reaction for fuel cell applications.