Title : Utilizing the undesirable oxidation of lead-free perovskite for photocatalytic C(sp3)─H activation: Unraveling the serendipity
Abstract:
Hybrid halide perovskites (HHPs), whose every branch generates intrusiveness, have been utilized in solar cells from a wider perspective. However, the inclusiveness of employing HHP as a photocatalyst is in its initial stage. This study mainly focuses on the unexpected utilization of so far undesirable material vacancy-ordered MA2SnBr6 quantum dots synthesized from MASnBr3 nanosheets. Here, the quantum confinement grounded a large blue shift in UV and PL spectra with a stokes shift of 420 meV, where the band gap increment is observed as size decreases in MA2SnBr6. Remarkably, MA2SnBr6 exhibits air and moisture stability, better charge transfer, and high oxidation potential in comparison to MASnBr3. The first principle-based atomistic computations reveal the strain relaxation in the Sn-Br framework that structurally stabilizes the MA2SnBr6 lattice. Furthermore, direct bandgap and strongly localized valence band edge give rise to a new potential photocatalyst MA2SnBr6 for efficient solar-driven C(sp3)─H activation of cyclohexane and toluene under ambient conditions. The as-synthesized MASnBr3 and its oxidized form having different ratios of Sn2+ and Sn4+ were subjected to cyclohexane oxidation and it was observed that the completely oxidized form i.e. MA2SnBr6 gave the highest yield of cyclohexanol (70 µmol/g) and cyclohexanone (87.6 µmol/g) within 6 h. The mechanism of the photo-oxidation of cyclohexane by MA2SnBr6 was probed thoroughly with a plethora of techniques and found that the formation of singlet oxygen is the main active species along with photogenerated holes in the oxidation of cyclohexane into K/A oils. In unconventional precedence, the present study opens new insight for MA2SnBr6 as a photocatalyst for such organic transformations and the new air and moisture-stable hybrid halide perovskites in general.1
