Preparation of N-doped microporous carbon nanospheres by direct carbonization of as-prepared mesoporous silica nanospheres containing cetylpyridinium bromide template

N-doped microporous carbon nanospheres (MCNs) are prepared directly from the as-prepared mesoporous silica nanospheres (MSNs) with a disordered pore structure by a new, simple and direct carbonization method. The as-prepared MSNs containing cetylpyridinium bromide (CTPB) template are effective for direct carbonization. Neither MSN with a two-dimensional hexagonal pore symmetry nor MSN with cetyltrimethylammonium bromide (CTAB) template is effective for this new method. Thus, this method is very cost-effective and environmentally benign. Furthermore, N-doping into the carbon matrix naturally occurrs during the carbonization process, because of the presence of pyridinium N atoms in the CTPB template. The N-doped MCN material is a good sorbent material for CO2 adsorption owing to the Lewis basic sites of N atoms as well as good microporosity. The low surface coverage isosteirc heat of CO2 adsorption (Qst) is calculated by the Clausius-Clapeyron equation using the data obtained at 273 and 298 K, and the calculated value of Qst is 58.4 kJ mol−1. This value is relatively very high compared to the other N-doped porous carbon materials. Both the Lewis basic sites of N atoms and uniform microporosity in the N-doped MCNs are responsible for this high value.