Lead halide perovskites for photocatalytic organic synthesis

Abstract

Nature is capable of storing solar energy in chemical bonds via photosynthesis through a series of C-C, C-O and C-N bond-forming reactions starting from CO₂ and light. Direct capture of solar energy for organic synthesis is a promising approach. Lead (Pb)-halide perovskite solar cells reach 24.2% power conversion efficiency, rendering perovskite a unique type material for solar energy capture. We argue that photophysical properties of perovskites already proved for photovoltaics, also should be of interest in photoredox organic synthesis. Because the key aspects of these two applications are both relying on charge separation and transfer. Here we demonstrated that perovskites nanocrystals are exceptional candidates as photocatalysts for fundamental organic reactions, for example C-C, C-N and C-O bond-formations. Stability of CsPbBr₃ in organic solvents and ease-of-tuning their bandedges garner perovskite a wider scope of organic substrate activations. Our low-cost, easy-to-process, highly-efficient, air-tolerant and bandedge-tunable perovskites may bring new breakthrough in organic chemistry.

Fig. 1

The library of C–C, C–N, and C–O bond formation reactions and respective yield. (Yields of 1a, 1c, 1d, 2a, 2g, 3a are the average yields of three reactions, see Supplementary Table 8; Inset: perspective view of 1d’s single crystal structure with the thermal ellipsoids drawn at 50% probability level and the H atoms omitted for clarity.)

Fig. 2

Characterization and spectroscopy studies of photocatalysts. a TEM of CsPbBr₃ P1; b P3; c P4; d UV-vis and PL spectra of CsPbBr₃ P2–P5; e PL spectra for P1 and P4 in CH₂Cl₂ as prepared and after LED irradiation for 24 h and 1 h, respectively. f XRD of as-prepared CsPbBr₃ P1; isolated from the reaction 1a before and after irradiation, respectively; g the corresponding XRD for reaction 1b; h PL spectra of P1 in THF with addition of TFA; i PL spectra of CsPbBr₃ NCs, Ir(ppy)₃, CdSe QDs and Ru(bpy)₃Cl₂ in air or N₂-saturated solutions. Source data are provided as a Source Data file

Fig. 3

Mechanisms. a Proposed mechanisms for the synthesis of 1c and 1d; b 2a and 2g. (Blue square: isolated and characterized by ¹H-NMR; Red square: trapped and detected by LC-MS (Supplementary Figs. 18–23); HT = hole-transfer; ET = electron-transfer)

Fig. 4

Band energy of CsPbBr₃ vs the redox potentials of substrates. Source data are provided as a Source Data file

Fig. 5

Band-tuning of perovskite. a The PL spectra of colloidal CsPbBr₃ in dichloromethane via band tuning with trimethylsilyl chloride or iodide and their representative images under UV lamp (top). b Bandedges of APbCl_xBr_yI_3-x-y. c Excited-state potential (E*) range of APbCl_xBr_yI_3-x-y comparing with noble transition-metal catalysts. d Two successful reaction examples with perovskite band-tuning. Source data are provided as a Source Data file