CsPbBr₃ Nanocrystals as Efficient Photocatalysts for Dehydrohalogenation: Toward Environmentally Friendly Trichloroethylene Synthesis

Abstract

The demand for a benign alternative to energy-intensive industrial chemical transformations is critical. Lead halide perovskites have emerged as promising candidates due to their unique optoelectronic properties, including high absorption coefficients in the visible region, tunable band gaps, and long charge carrier-diffusion lengths. In this study, we present a model reaction to showcase the photocatalytic utility of perovskite nanocrystals (NCs). Specifically, we demonstrate the synthesis of trichloroethylene (TCEt) from 1,1,2,2-tetrachloroethane (TCE) using CsPbBr 3 NCs under white light illumination. The band-edge positions of the NCs and the redox potential of TCE enable efficient electron transfer for C−Cl bond activation. Furthermore, while ensuring operational stability, CsPbBr 3 NCs undergo lightcontrolled modification, leading to the formation of mixed-halide perovskite (CsPbBr x Cl 3−x ) NCs during the reaction. This procedure yields a mixed-halide perovskite that maintains stability while containing the desired halide content. Additionally, the reaction produces HBr as a byproduct, serving as a self-cleaning technique to eliminate excess Br − ions from the solution. Ultimately, we achieve nearly 100% conversion of CsPbBr 3 to pure CsPbCl 3 NCs, with a full width at half-maximum of approximately 11.2 nm. Our clean and efficient approach to synthesizing TCEt using perovskite NCs provides interesting insights into violet light-emitting diode (LED) fabrication and color patterning. This study highlights the promising potential of perovskite materials for sustainable chemical transformations and optoelectronic applications.

Metal Halide Perovskite Nanocrystals for C–X Activation: Role of Halide Vacancies

“…Recent studies on photoinduced halide exchange reactions have emphasized the critical role of halide vacancies in C–X bond cleavage. ,, Our findings experimentally support this mechanism. OAm ligands, known for their dynamic binding to CsPbBr 3 NCs (eq 1), establish an equilibrium between oleylammonium bromide (OAmBr) and oleylammonium-NCs.…”

“…Following the previous reports on C–X activation, we strategized to probe adsorption sites for the C–X bond on the surface of the CsPbBr 3 NCs. ,, To do so, the mixture of dichloromethane (DCM) and hexane in a ratio of 2:1 was used as a solvent-cum-reactant to dissolve CsPbBr 3 NCs capped with various ligands while maintaining the excitonic absorbance value at ∼0.1. The DCM serves as a source of C–Cl bonds, which can be activated photocatalytically upon light irradiation.…”

“…C–X bond activation represents a specific and intriguing area of photocatalytic organic transformation. ,,− Recent research has demonstrated the ability to activate C–X bonds in alkyl halides via photoassisted anion exchange reactions using perovskites. ,, This light-controlled approach offers significant advantages, allowing for the reaction to be carried out under ambient conditions with near-perfect conversion. This paves the way for exciting possibilities beyond photocatalysis, extending to the potential use of perovskite NCs in light-emitting diodes for display technologies. − …”

Halide perovskite for enhancing photocatalytic efficiency: basic characteristics, nanostructure engineering and applications

“…In addition, the unique intrinsic properties of halide perovskites warrant discussion. Singh et al 141 used CsPbBr 3 nanocrystals to synthesize trichloroethylene (TCEt) from 1,1,2,2-tetrachloroethane (TCE) under white light illumination (Fig. 17).…”