Constructing homo/hetero-nuclear carbon and oxygen atoms co-doped graphitic carbon nitride assisted by ionic liquid for photothermal synergistic catalytic oxidation of cyclohexane.

The adoption of photothermal synergistic catalysis for cyclohexane oxidation can balance the advantages of high conversion of thermal catalysis and high selectivity of photocatalytic technology to achieve better catalytic performance. Here, we prepared functional carbon nitride (BCA-CN) by self-assembly strategy of ionic liquid [Bmim]CA (1-Butyl-3-methylimidazole citrate) with melamine and cyanuric acid utilizing abundant elements and anionic/cationic hydrogen bonding interactions. The introduction of [Bmim]CA embeds C-C (carbon and carbon band) and C-O-C (ether bond) structures into graphitic carbon nitride (g-CN) framework, significantly improving light absorption capacity and migration of photo generated charge carriers. Compared to g-CN, both BCA-CN increases cyclohexane conversion and KA oil (the mixture of cyclohexanol and cyclohexanone) selectivity by 1.3 times under photothermal catalysis. The surface reactions are facilitated by changing adsorption sites of cyclohexane to increase adsorption energy and obtaining more hydroxyl radicals and superoxide radicals. Furthermore, the enhanced selectivity is attributed to the difficulty in generating cyclohexanone radicals. This work offers the reference scheme for the development of efficient photothermal catalysts in the selective oxidation of cyclohexane.