Designing CdS/Zn(impim) Dots-on-Rods for Enhanced Visible-Light-Driven Reduction of C-X Bonds: Exploring Electron Transfer Dynamics

Utilizing solar energy for the cleavage of C-X bonds in halogenated organic compounds, leading to the formation of C-H bonds, holds potential for both environmental pollution control and significant organic conversion reactions.

In a recent publication in ACS Applied Materials & Interfaces, Prof. Cao Rong’s research group from the Fujian Institute of Research on the Structure of Matter of the Chinese Academy of Sciences presented a study on a coupled CdS/Zn(impim) system. They delved into the electron transfer kinetics involved in the photocatalytic reduction of C-X bonds for CdS/Zn(impim) composites.

The researchers synthesized a composite photocatalyst of CdS/Zn(impim) (MOF) dots-on-rods under mild conditions, meticulously characterizing its structure and morphology using techniques such as powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM).

Their findings highlighted that CdS nanoparticles were evenly distributed on the surface of rod-shaped Zn(impim) MOF, facilitating the separation of electron-hole pairs. To confirm the electron transfer from CdS to Zn(impim), the team measured surface work functions using Kelvin probe force microscopy (KPFM). They also observed a significant reduction in the fluorescence lifetime of CdS/Zn(impim) compared to CdS, and they detailed the relevant electron transfer kinetics through fluorescence spectrum and femtosecond transient absorption spectroscopy (fs-TAS).

In order to showcase the photocatalytic capabilities of CdS/Zn(impim), the researchers selected α-bromoacetophenone, bromobenzonitrile, and their derivatives as model reactions. Their results demonstrated markedly higher photocatalytic dehalogenation activity with the CdS/Zn(impim) composite compared to CdS or Zn(impim) alone. The catalyst exhibited excellent stability, maintaining its morphology and structure even after five consecutive cycles.

In the dehalogenation reaction of α-bromoacetophenone, the researchers utilized electron paramagnetic resonance (EPR) to detect the intermediate acetophenone radical, providing insights into the reaction’s intermediate process.

When subjected to visible light irradiation, CdS experienced excitation of electrons, which were then transferred to Zn(impim). Meanwhile, holes were retained in CdS, enabling efficient charge separation and retarding the charge recombination process. Ultimately, this mechanism enhanced the efficiency of photocatalytic dehalogenation.

This study significantly contributes to our understanding of the electron transfer mechanism in semiconductor/MOF composites and sheds light on the photocatalytic halide dehalogenation process, offering a viable approach to designing high-performance photocatalytic materials.

Source: Chinese Academy of Sciences

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