Two Pseudo-Polymorphic Porous POM-pillared MOFs for Sulfide-Sulfoxide Transformation: Efficient Synergistic Effects of POM Precursors, Metal Sites and Microstructures

Developing sustainable and powerful heterogeneous catalytic systems to convert sulfides into high-value sulfoxide products has become a particularly appealing field and an arduous chal-lenge.In this work,two porous polyoxometalate-pillared metal-organic frameworks,formulated as H3n[Cu3(pidc)2(H2O)2.5]2[PW12O40]n·xH2O(n=1.5,x=6 for 1,n=1,x=12 for 2;and H3pidc=2-(3-pyridinyl)-1H-imidazole-4,5-dicarboxylic acid),were consciously manufacture and employed for hetero-geneously catalyzed sulfide-sulfoxide transformation.Structural analysis shows that 1 and 2 exhibit sim-ilar porous frameworks with nearly identical two-dimensional metal-organic layers further pillared by tetradentate POM ligands with different coordination modes,which also result in the porosity of 1 be-ing almost twice that of 2.In catalyzing the conversion of methyl phenyl sulfide(MPS)to methyl phenyl sulfoxide(MPSO),1 can convert nearly 100％of MPS into MPSO within 30 min,while 2 achieved the similar results requires 50 min.The higher activity of 1 may be attributed to its larger channel that can provide more active sites and more efficient mass transfer process.Systematic structure-activity analyses and mechanistic studies revealed dual-reaction pathways driven by POM sites and metal sites assisted by the structural microenvironment.