Highly Efficient Yolk-Shell Photocatalyst Constructed by Integration of NiP and CuO Nanoparticles to Defective Metal-Organic Frameworks for Visible-Light-Driven Amine Oxidation.

Realizing the directional migration of photogenerated carriers plays an important role in improving the photocatalytic performance. Meanwhile, light-driven oxidative coupling of benzylamine under ambient conditions with an inexpensive catalyst is highly desirable for the industrial field. Herein, via in situ synthesis, defect engineering, and photodeposition, a yolk-shell nanostructured photocatalyst, NiP@OH-NH-UiO-66@CuO, featuring nickel phosphide (NiP) nanoparticles (NPs) trapped inside a defect engineered metal-organic framework (MOF, namely OH-NH-UiO-66) and CuO NPs adhering on the surface of MOFs, has been rationally fabricated for the achievement of spatial separation of oxidation/reduction cocatalyst in photocatalytic reaction systems. The yolk-shell structure can effectively avoid the aggregation of the NiP and CuO NPs. Remarkably, the separation of electron collector NiP and hole collector CuO regulates the directional movement of the photogenerated carriers and effectively improves the electron-hole separation efficiency to generate abundant reactive superoxide radicals (O) and hydroxyl radicals (OH). NiP@OH-NH-UiO-66@CuO achieves a conversion of 99% for the oxidative coupling of benzylamine into imine within 1 h at ambient temperature under visible-light irradiation. The present study provides an economical method to construct a MOF-based yolk-shell photocatalyst for the oxidative coupling of amines.