Effect of exposed facets of bismuth vanadate, controlled by ethanolamine, on oxidative coupling of primary amines

This work firstly demonstrates the ethanolamine (ETA)-assisted hydrothermal synthesis of BiVO₄, with different ratios of exposed {110}/{010} planes and relates this to performance in photocatalytic oxidative coupling of benzylamine under visible light. {110}-dominant BiVO₄ exhibits outstanding photocatalytic activity at room temperature owing to synergistic effects of largely exposed {110}-oxidative facet along with excellent charge generation and migration abilities, as evidenced by X-ray diffraction patterns, electrochemical impedance spectra, and photocurrent responses. The catalyst can successfully transform benzylamine derivatives to corresponding imines with selectivities of >85%, indicating a wide scope of amine substrates that can be used with the developed catalyst. Based on radical scavenging, spin-trapping EPR, and Mott-Schottky results, a plausible oxidative coupling mechanism via a O₂^--assisted route and band energy diagram of the catalyst are proposed. This work highlights the influence of ETA in controlling resultant exposed crystal facets of the final BiVO₄, which is the main factor governing oxidative amine coupling activity. Importantly, the tunability of exposed {110}/{010} facet of BiVO₄ controlled by ETA as well as a correlation between {110} facet and the coupling activity of benzylamine firstly disclosed in this work could be readily extended for designing functional catalysts with desired performances.