Ionic liquids assisted synthesis of graphite carbon nitride for one-pot aerobic oxidation of cyclohexane to adipic acid

Adipic acid (AA) is a crucial intermediate in the production of nylon monomers, which is generally obtained by the oxidation of cyclohexane. However, difficult C -H activation and easy overoxidation make it extremely challenging to obtain highly selective AA. Herein, ionic liquid (IL) assisted synthesis of graphitic carbon nitride (g-C3N4) was designed for one -pot oxidation of cyclohexane to AA. The incorporation of C and S elements and the formation of N vacancies were brought with the presence of IL. 26.1% conversion and 51.2% AA selectivity were achieved over [Bmim][HSO4] (1-Butyl-3-methylimidazolium hydrogen sulfate) modified g-C3N4, which significantly increased AA selectivity by 18% compared to unmodified g-C3N4. The changes in electronic structure of gC3N4 were assumed resposible for the improvement of AA selectivity by increasing the adsorption of cyclohexanone. Besides, the reduction of alkaline sites caused by the introduction of S atoms and N vacancies was benefit to remove AA avoiding excessive oxidation.