Microwave-assisted construction of 2D/2D direct Z-scheme g-C3N4/Bi4O5Br2 heterojunctions with enhanced molecular oxygen activation for boosting selective photocatalytic conversion of benzyl alcohol

Novel 2D/2D g-C3N4/Bi4O5Br2 heterojunctions were constructed via a facile microwave-assisted tactic, which exhibited excellent selective photocatalytic oxidation of benzyl alcohol under blue LED light. The reaction rate of the optimized sample was approximately 9.2 and 5.3 times higher than those of g-C3N4 or Bi4O5Br2 alone, respectively, with more than 99% selectivity for benzaldehyde. DFT calculations and experimental studies showed that there was no chemical bonding between Bi4O5Br2 and g-C3N4, but a direct Z-scheme system was created through weak van der Waals interactions. Electron spin resonance and radical quenching experiments revealed that the primary reactive species in the photoreaction system were superoxide radicals (•O2–) and holes (h+). Accordingly, the boosted photocatalytic activity of g-C3N4/Bi4O5Br2 heterojunctions arose from its optimized energy band configuration and van der Waals Z-scheme system, which effectively activated molecular oxygen to generate •O2– and triggered the first step in the photoconversion of benzyl alcohol. This work demonstrates the crucial role of semiconductor band regulation in selective photocatalytic organic conversion and the effective activation of molecular oxygen by rational design of heterogeneous interfaces.