Iron sites on defective BiOBr nanosheets: Tailoring the molecular oxygen activation for enhanced photocatalytic organic synthesis

Abstract

Sunlight-driven activation of molecular oxygen (O 2 ) for organic oxidation reactions offers an appealing strategy to cut down the reliance on fossil fuels in chemical industry, yet it remains a great challenge to simultaneously tailor the charge kinetics and promote reactant chemisorption on semiconductor catalysts for enhanced photocatalytic performance. Herein, we report iron sites immobilized on defective BiOBr nanosheets as an efficient and selective photocatalyst for activation of O 2 to singlet oxygen ( 1 O 2 ). These Fe 3+ species anchored by oxygen vacancies can not only facilitate the separation and migration of photogenerated charge carrier, but also serve as active sites for effective adsorption of O 2 . Moreover, low-temperature phosphorescence spectra combined with X-ray photoelectron spectroscopy (XPS) and electronic paramagnetic resonance (EPR) spectra under illumination reveal that the Fe species can boost the quantum yield of excited triplet state and accelerate the energy transfer from excited triplet state to adsorbed O 2 via a chemical loop of Fe 3+ /Fe 2+ , thereby achieving highly efficient and selective generation of 1 O 2 . As a result, the versatile iron sites on defective BiOBr nanosheets contributes to near-unity conversion rate and selectivity in both aerobic oxidative coupling of amines to imines and sulfoxidation of organic sulfides. This work highlights the significant role of metal sites anchored on semiconductors in regulating the charge/energy transfer during the heterogeneous photocatalytic process, and provides a new angle for designing high-performance photocatalysts.

Highly selective generation of singlet oxygen from dioxygen with atomically dispersed catalysts

“…27,28 Despite the simplicity and controllability of the photosensitization route, it faces inherent limitations like poor selectivity of 1 O 2 , photobleaching of sensitizers, and difficulty in large-scale production. [29][30][31] Therefore, development of new approaches to highly selective production of 1 O 2 is of great signicance not only in the investigation of 1 O 2 -related biological and physical processes but also in the development of new materials and biological tools with 1…”

Construction of Hexagonal Prism-like Defective BiOCL Hierarchitecture for Photocatalytic Degradation of Tetracycline Hydrochloride

“…To provide insight into the underlying reasons for the superior photocatalytic activity of the target specimens, UV/Vis absorption, photoluminescence (PL), and photo-electro-chemical characteristics of BiOCl and 3D-BiOCl were investigated. Generally, lattice defects in semiconductor material would result in changes in the energy band structure, so as to alter the light absorption capabilities of material [ 15 , 51 , 52 ]. To this end, UV/Vis diffuse reflectance spectra were first performed to investigate the optical absorption properties of BiOCl and 3D-BiOCl.…”

Manipulating Excitonic Effects in Layered Bismuth Oxyhalides for Photocatalysis

“…To strengthen O 2 adsorption and prompt exciton-dominated O 2 activation, Lu et al proposed another strategy by anchoring Fe atoms onto the oxygen vacancies of BiOBr–(001) surface (BiOBr OV –Fe) via a multistep wet impregnation method (Figure a) . Steady-state of BiOBr OV –Fe displayed a stronger PH emission peak than BiOBr OV , indicating the intersystem crossing (ISC) positively contributed to the formation of triplet excitons.…”

“…EPR spectra with the addition of (b) TEMP and (c) DMPO. (d) Schematic illustration of anchored Fe on the promoted photocatalytic activation of O 2 to 1 O 2 (Reprinted with permission from ref . Copyright 2021 Springer).…”