Enhanced Carrier Separation in Visible-Light-Responsive Polyoxometalate-Based Metal–Organic Frameworks for Highly Efficient Oxidative Coupling of Amines

Photocatalytic
technology is widely studied, while it comes with
drawbacks such as low sunlight utilization efficiency and high carrier
recombination rates. Herein, for the first time, we present two crystalline
polyoxometalate (POM)-based metal–organic frameworks (POMOFs),
{[Cd­(DMF)2Ru­(bpy)2(dcbpy)]2(POMs)­(DMF)2} xDMF (PMo-1, POMs = [PMoVI11MoVO40]4–, x = 5; SiW-2, POMs = [SiW12O40]4–, x = 4) through
assembling the photosensitizer [Ru­(bpy)2(H2dcbpy)]­Cl2 and POMs into a single framework. The assembly not only enhances
light absorption in the visible light regime but also improves carrier
separation efficiency; atop of that, both POMOFs demonstrate activities
in the photocatalytic oxidative coupling of amines. Particularly, PMo-1 enables the quantitative completion of oxidative coupling
of benzylamine reaction within 30 min (yield = 99.6%) with a high
turnover frequency (TOF = 6631.6 h–1). To our knowledge,
the PMo-1 catalyst outperforms any other photocatalysts
previously reported in similar use cases where TOF values were usually
obtained <2000 h–1.