Emulsion of Benzene and Water Phases by an Amphiphilic Hematite/Carbon Nitride Photocatalyst for Phenol Synthesis
Ningxi Su, Dexi Yu, Shengyang Zhong, Mei‐Rong Huang, Yidong Hou, Masakazu Anpo, Jimmy C. Yu, Jinshui Zhang, Xinchen Wang
Abstract
Photocatalytic hydroxylation of benzene in water using H 2 O 2 as the oxidant is a green approach toward phenol synthesis. However, the immiscibility of benzene in water results in poor photocatalytic performance and a low efficiency of H 2 O 2 utilization. To enhance drastically the affinity between the aqueous and nonaqueous phases, an amphiphilic heterojunction (Fe 2 O 3 /crystalline carbon nitride (CCN)) has been synthesized by intimately immobilizing hematite (Fe 2 O 3 ) nanoparticles on a CCN surface for the photocatalytic hydroxylation of benzene to phenol. The unique amphiphilicity of Fe 2 O 3 /CCN allows the formation and stabilization of homogeneous emulsions in a benzene/water mixture to increase the effective oil/water interface area for more efficient mass transport. Moreover, the well-established type II heterojunction between Fe 2 O 3 and CCN facilitates the fast separation and transfer of photoelectrons from CCN to Fe 2 O 3 for the photo-Fenton activation of H 2 O 2 with high utilization efficiency. We recorded a maximum phenol conversion of 31.6% by using a stoichiometric amount of H 2 O 2 (10 mmol) on the photocatalytic hydroxylation of benzene. The apparent quantum yield of phenol production at λ = 420 nm was determined to be 47.1%. This amphiphilic photocatalyst approach would be useful for realizing other advanced oxidation reactions involving immiscible components.