Integration of CdS Nanoparticles and Molecular Cobalt Catalysts into Metal–Organic Frameworks for Highly Efficient Photocatalytic Amine Oxidation

The rational design and construction of metal–organic framework (MOF)-based photocatalytic composites with outstanding visible-light responsiveness, rapid photogenerated charge carrier separation and migration ability, and suitable band gaps for photocatalytic organic transformation have gained enormous attention, yet they are highly challenging. Herein, a series of hybrid materials, CdS-x/UiO-66-IPy(Co) (x represents the theoretical loading amount of CdS into the synthetic system), featuring CdS nanoparticles and molecular cobalt centers, have been constructed by a step-by-step assembly (SSA) strategy. Significantly, the resultant CdS-x/UiO-66-IPy(Co) composites present dramatically improved catalytic activity in the oxidative coupling of amines under ambient air and visible-light irradiation (λ > 400 nm) as compared with the parent UiO-66 and CdS. Specifically, CdS-20/UiO-66-IPy(Co) can efficiently convert benzylamine derivatives into the target imine products with conversion and selectivity both exceeding 95%, attributed to the formation of a heterostructure between the well-dispersed CdS nanoparticles, molecular Co catalyst, and UiO-66-NH2, which facilitated an extended range of light absorption, efficient separation and migration of photogenerated charge carriers, and abundant exposed reaction active sites. The recycling experiments confirm the good recyclability and durability of CdS-20/UiO-66-IPy(Co). Furthermore, the underlying catalytic mechanism has been well established by comprehensive experiments involving photocurrent, electrochemical impedance, photoluminescence, transient absorption, and electron paramagnetic resonance spectroscopy measurements.