Construction of MnCo2S4/S-BiOCl S-Scheme Heterojunction Nanocatalysts for Efficient Visible-Light-Driven Oxidative Coupling of Benzylamine via Cooperative Electron–Hole Utilization

Abstract Photocatalytic selective oxidation of amines to imines has attracted wide attention because of the high value of imines in pharmaceuticals, agrochemicals, and fine chemicals. However, most photocatalysts are constrained by insufficient visible-light absorption, rapid charge recombination, and inadequate redox capability. Herein, we report the fabrication of an in situ-grown MnCo2S4/S-BiOCl (MSB) S-scheme heterojunction nanocatalyst by a simple solvothermal method for photocatalytic oxidative coupling of benzylamine (BA) to N-benzylbenzaldimine (BBAD). The S-scheme heterojunction accelerates charge transfer and inhibits electron–hole recombination owing to the tight interface and internal electric field. More importantly, photogenerated holes initiate BA activation, while electrons reduce O2 to generate superoxide radicals that facilitate the subsequent oxidative coupling process, enabling cooperative electron–hole utilization. Meanwhile, the fabricated MSB exhibits enhanced visible-light harvesting, abundant active sites, and strong redox capability. Consequently, optimal MSB-10 achieves 99% BA conversion and 98% BBAD yield under 395 nm LED irradiation with good stability after six cycles. This work demonstrates an effective strategy for constructing high-performance S-scheme heterojunction photocatalysts and highlights the importance of cooperative electron–hole utilization in photocatalytic oxidative coupling reactions.