Multipath charge transfer in Cu-BTC@CuS@CeO2 double p-n heterojunction hollow octahedrons for enhanced photocatalytic amine oxidation

Hollow heterostructured catalysts have been widely investigated and applied in photocatalytic organic reactions. However, achieving hybrid catalysts with optimized hollow structure and controllable components is still a challenge. Herein, Cu-BTC@CuS@CeO2 ternary heterostructure hollow octahedrons were designed and prepared using a copper-based metal–organic framework (Cu-BTC) as both copper source and template. A thin CeO2 nanolayer was first formed and covered on the prepared Cu-BTC octahedron surface through a hydrothermal process. In the meanwhile, the Cu-BTC octahedrons were controllably etched in this hydrothermal process, leading to the formation of Cu-BTC@CeO2 hollow octahedron. The following sulfidation reaction produced Cu-BTC@CuS@CeO2 double p-n heterojunction hollow octahedrons. Benefiting from the novel hollow octahedron double p-n heterojunctions, excellent visible-near infrared light absorption, and fast charge transfer and separation, the obtained Cu-BTC@CuS@CeO2 hollow octahedron hybrid catalyst exhibited a significantly higher photocatalytic activity toward the oxidative coupling of amines to imines at room temperature under visible-near infrared light irradiation compared to the control single component catalysts (Cu-BTC, CeO2, and CuS) and binary hybrid catalysts (Cu-BTC@CeO2, Cu-BTC@CuS, and CuS@CeO2). The enhanced charge transfer at the double p-n heterojunction was discussed. Meanwhile, the photocatalytic oxidation products and reaction mechanism were investigated by surface-enhanced Raman spectroscopy, gas chromatography-mass spectrometry, and pyridine adsorption FT-IR spectroscopy. This work presents a promising strategy for the design of multi-component hollow heterostructure catalysts.