Efficient metal-free aerobic oxidative desulfurization with nitrogen and sulfur co-doped covalent organic polymer-derived carbon

A nitrogen and sulfur co-doped carbon was prepared from a covalent-organic polymer named microporous triazine polymer (MCTP) for the first time by loading NH4NO3 and diphenyldisulfide followed by pyrolysis. The obtained carbons (named NSMDCs) were exploited as environment-friendly metal-free catalysts for oxidative desulfurization of organo sulfurous compounds (OSCs) from a dodecane-based simulated fuel using molecular oxygen (O2) as an oxidizing agent. One of the materials showed a nearly complete conversion of an OSC, dibenzothiophene, after a reaction of 4 h at 100 degrees C which is one of the lowest temperatures among the metal-free ODS catalyses. A very low activation energy (Ea) of 30.4 kJmol-1 was found for the DBT oxidation which is also lower than or competitive against most of other reported results (including the ones using metal-based catalysts). Radical scavenging investigations and ESR analyses showed the generation of superoxide anion radicals (O2-& BULL;) from O2 that might have a dominant role in the oxidation or ODS. Moreover, DFT calculation revealed the generation of increased charge difference on the surface of the N and S co-doped catalyst. A plausible reaction mechanism including the effective activation of O2 was proposed. The catalyst was effectively used for at least five runs without noticeable degradation with simple acetone soaking and further washing.