Solvent-modulated assembly of peptide and cerium functionalized gigantic {Mo120Ce6}2 dimers for high-efficiency photocatalytic oxidation

Abstract

The controlled synthesis of gigantic polyoxometalates (POMs), as structural model compounds of metal oxides, with tailored functionalities is critical for the understanding of their self-assembly and structure–function relationship; yet, it is very challenging as it requires precise modulation of the connection modes between both fundamental building blocks and imported functionalities on such colossal skeletons. Herein, we describe the controlled synthesis of two types of gigantic POM dimers {Mo₁₂₀Ce₆}₂, 1 and 2, by applying methanol as a modulating solvent and Ce^III ions and peptides as functionalities. Upon adoption of methanol as the second solvent together with water, the connection between two {Mo₁₂₀Ce₆} monomers and the way peptides anchor on the surfaces can be well tuned, thus facilely driving the structural transformation from 1 to 2. A rational combination of all these functionalities within porous 1 and 2 realizes the photocatalytic aerobic oxidation of sulfides to sulfoxides. Control experiments revealed that 1 showed the best photocatalytic performance towards a variety of sulfides (yield and selectivity up to 98%) due to the synergistic effect of Ce^III sites, the porous skeleton with the optimal cavity and microenvironment as well as surfactant-like peptides. This work may provide a viable strategy by using solvents as modulators to build more gigantic POM clusters with emerging functions.