Achieving High Selectivity in Photocatalytic Oxidation of Toluene on Amorphous BiOCl Nanosheets Coupled with TiO₂

Abstract

The inert C(sp 3)–H bond and easy overoxidation of toluene make the selective oxidation of toluene to benzaldehyde a great challenge. Herein, we present that a photocatalyst, constructed with a small amount (1 mol %) of amorphous BiOCl nanosheets assembled on TiO2 (denoted as 0.01BOC/TiO2), shows excellent performance in toluene oxidation to benzaldehyde, with 85% selectivity at 10% conversion, and the benzaldehyde formation rate is up to 1.7 mmol g–1 h–1, which is 5.6 and 3.7 times that of bare TiO2 and BOC, respectively. In addition to the charge separation function of the BOC/TiO2 heterojunction, we found that the amorphous structure of BOC endows its abundant surface oxygen vacancies (Ov), which can further promote the charge separation. Most importantly, the surface Ov of amorphous BOC can efficiently adsorb and activate O2, and amorphous BOC makes the product, benzaldehyde, easily desorb from the catalyst surface, which alleviates the further oxidation of benzaldehyde, and results in the high selectivity. This work highlights the importance of the microstructure based on heterojunctions, which is conducive to the rational design of photocatalysts with high performance in organic synthesis.

Visible-Light-Driven Toluene Oxidation to Benzaldehyde over WO3 Nanostructures

“…Based on the findings from our study and the existing literature, we propose a series of steps involved in the photocatalytic oxidation of toluene over WO 3 , as depicted in Figure . The process can be outlined as follows:…”

Bis-ferrocenyl-hydrazide metal complexes: studying electronic functional groups as newly potent homogeneous photocatalysts for C(sp3)–H and C(sp2)–H bond oxidation utilizing visible light condition

“…102,103 Finally, intermediate II leads to the formation of an oxygenated compound (benzaldehyde). 104…”

The multiple roles of rare earth elements in the field of photocatalysis

“…6–11 People have discovered that photocatalytic reactions play significant roles in many research fields, including photocatalytic CO 2 reduction, pollutant degradation, multi-carbon-based material synthesis, water pollution control, and others. 12–22 The mechanism of the photocatalytic reaction has also been confirmed by scientists: when a beam of light is irradiated on the semiconductor photocatalyst, the energy of the incident light ( hυ ) is higher than the forbidden bandwidth ( E g ) of the semiconductor, the electrons (e − ) in the valence band are excited to transition to the conduction band, and at the same time, the valence band produces holes (h + ), and under the action of the electric field, the e − and h + diffuse to the surface of the catalyst, and the e − and h + are separated efficiently so that the conduction band and the valence band have the capacity to oxidize and reduce, respectively, which can have a redox reaction with the surface adsorption of the material to produce a product in line with the expectation of the people. 23–26 Therefore, photocatalytic reactions are one of the most promising solutions to the environmental and energy crisis through the efficient and rational use of sunlight for redox reactions.…”