Direct Synthesis of Nitrogen-Doped Carbon Materials from Protic Ionic Liquids and Protic Salts: Structural and Physicochemical Correlations between Precursor and Carbon

The traditional preparation of carbon materials requires specific polymer precursors and complex procedures. In this work, a series of easily prepared protic ionic liquids and salts (PILs/PSs) based on widely obtainable N-containing bases and acids were synthesized and explored as novel small-molecule precursors for preparing carbon materials via direct carbonization. Protonation enables nearly all N-containing compounds to be directly carbonized to carbon materials without the additional catalyst, tedious synthesis, vacuum system, and etching step that are often involved with conventional precursors. The correlations between the organic precursors and the properties of the carbon materials, in terms of yield, graphitization, N content, thermal stability against oxidation, and porosity, were systematically investigated. Based on the molecular tunability of PILs/PSs, it was possible to obtain task-specific carbon materials through ab initio design of the precursors at the molecular level. Importantly, highly porous N-doped carbons were obtained by one-step, template-free carbonization of certain PILs/PSs, and these carbon materials were found to exhibit high CO₂ uptake at room temperature and ambient pressure. Carbon materials obtained using this inexpensive strategy may find advanced applications in the fields of catalysis, energy, and environmental treatment.