Photocatalytic one-pot alkylation of nitrobenzene with benzyl alcohol for the precise synthesis of N-benzylideneaniline over F-doped Bi2MoO6 nanosheets

Monolayer Bi2MoO6 nanosheets doped with F atoms (F-BMO-NSs) were developed as catalysts for the one-pot alkylation of nitrobenzene with benzyl alcohol. 95.88% conversion of nitrobenzene coupled with 99.98% selectivity of n-benzylideneaniline was achieved over the F0.04-BMO-NSs under visible light irradiation and 1 atm N2 at room temperature. XPS and EPR results suggested that F doping not only produced enhanced Lewis acid sites (Bi3+ and Mo6+), but also generated Lewis base sites (Mo5+). In situ FTIR spectra revealed that benzyl alcohol would be selectively adsorbed on the enhanced Lewis acid sites via Bi3+ (Mo6+)⋯OH–C– interface coordination, resulting in the activation of HO–C–. Moreover, nitrobenzene would be chemisorbed on the Mo5+ basic sites via Mo5+⋯NO2 coordination, inducing charge transfer from Mo5+ to –NO2. Under visible light irradiation, hydrogen transfer takes place from the chemisorbed benzyl alcohol to nitrobenzene generating benzaldehyde and aniline, finally coupling to form the imine. Based on these surface cooperated functional sites, a synergistic mechanism has been proposed to elucidate the accurate structure–performance relationship. This work provides a new perspective for the design of high activity, high selectivity and high stability photocatalysts for the precise synthesis of imines.