Revisiting the Stӧber method: Design of nitrogen-doped porous carbon spheres from molecular precursors of different chemical structures.

Porous polymer resins and carbon spheres have been successfully prepared by an extended Stӧber method using phenol derivatives of different functionality. Herein, the Stӧber method is revised and used for the preparation of phenolic resin spheres from a series of hetero-atoms containing phenol derivatives (such as nitrophenol, aminophenol and halide-substituted phenols), which upon carbonization are converted to heteroatom-doped carbon spheres. The use of 4-amino-3-nitrophenol affords monodispersed carbon spheres with unprecedentedly high nitrogen content of about 11.9wt%. In this synthesis phenolic resin is initially formed by polymerizing formaldehyde with one of the aforementioned phenol derivatives, which acts as a resin precursor and source of heteroatoms to be doped. When amino group in aminophenol is in meta position the monodisperse phenolic resin and subsequently converted-doped carbon spheres are obtained. The resultant carbon spheres were examined as potential CO2 adsorbents and electrode materials for supercapacitors, reaching CO2 uptake of 89cm(3) STP/g (at 273K and 1.0bar), and the electrochemical capacitance of 127 F/g under basic conditions, respectively. This study provides some guidelines for design of carbon spheres by selecting phenolic resin precursors with desired molecular structures and functionalities for specific applications.