Photocatalytic Synthesis of Aromatic Nitriles Using TiO₂ Nanotubes Decorated With Bismuth Halide Perovskite Nanodots

The aromatic nitrile synthesis via ammoxidation of methylarenes typically requires harsh reaction conditions (≥ 350°C or ≥ 15 bar O₂). Here, TiO₂ nanotubes (NTs) homogeneously decorated with halide perovskite Cs₃Bi₂Br₉ (CBB) nanodots (< 2 nm) were established as efficient photocatalysts for the sustainable synthesis of aromatic nitriles. A yield rate up to 353 µmol g^-1 h^-1 was achieved under mild conditions (100°C-120°C, 1-4 bar, and blue light irradiation) with decent nitrile selectivity (85%-88%). Enhanced photo-induced charge diffusion and structural stability of CBB nanodots afforded excellent quantum efficiencies (up to 26.7%) and sustained photocatalytic activity in long-term ammoxidation (45 h). Additionally, 11 methylarenes were successfully converted to the corresponding nitriles over the CBB/TiO₂ NT photocatalyst. Mechanism investigations revealed a synergistic catalytic effect between perovskite nanodots and TiO₂ NTs. CBB nanodots activated benzylic C(sp³)-H bonds and promoted the oxidation of aldimine intermediates, while TiO₂ NTs with unique adsorption of alcohol intermediates accelerated their partial oxidation to aldehydes.