Self-assembly of polyoxometalates, Pt nanoparticles and metal-organic frameworks into a hybrid material for synergistic hydrogen evolution

A polyoxometalate (POM), Pt nanoparticles (NPs) and a metal-organic framework (MOF, NH2-MIL-53) self-assemble into a hybrid material, PNPMOF, that displays synergistic activity for visible-light-driven catalytic hydrogen evolution (the PNPMOF is far more active than any of the three functional components alone). The POM has four targeted functions in this hybrid material: it reduces H2PtCl6 to Pt NPs, stabilizes the Pt NPs, induces a strong electrostatic association of the negatively charged Pt NPs with the protonated NH2-MIL-53 sites on the particle surfaces, and facilitates the catalytic reduction reaction itself. The NH2-MIL-53 in this work protects the light sensitive 2-aminoterephthalate groups in the pores from oxidation by the POMs, while the surface protonated NH2 units on the MOF particle surfaces strongly bind the negatively charged POM-stabilized Pt NPs.