Dual-metal Ni and Fe phthalocyanine/boron-doped g-C3N4Z-scheme 2D-heterojunctions for visible-light selective aerobic alcohol oxidation

Abstract

The rational development of g-C₃N₄-based photocatalysts remains a great challenge for selective aerobic alcohol oxidation. Herein, sub-nanoscale nickel phthalocyanine (NiPc)–iron phthalocyanine (FePc) J-type aggregates were assembled on boron-doped g-C₃N₄ (BCN) driven by H-bonding interactions to obtain novel dimension-matched NiPc–FePc/BCN heterojunctions. The optimal NiPc–FePc/BCN photocatalyst, found by altering the Ni : Fe ratio, achieves an 8-fold visible-light conversion rate as compared to that of CN for benzyl alcohol (BA) oxidation and nearly 100% selectivity to benzyl aldehyde (BAD). The enhanced photoactivity is attributed to the wide-spectrum light absorption and more importantly, the facilitated charge separation due to cascade Z-scheme electron transfer from BCN to FePc and then to NiPc, evidenced by experimental and theoretical results. Notably, the synergy of NiPc and FePc was found to promote the catalytic O₂ reduction to produce reactive ˙O₂⁻ radicals, which dominate the selective oxidation with the mild holes of BCN. This work showcases a novel strategy for developing advanced Z-scheme photocatalytic systems for green organic synthesis.