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 challenge.In this work,two porous polyoxometalate-pillared metal-organic frameworks,formulated as H_(3n)[Cu_(3)(pidc)_(2)(H_(2)O)_(2.5)]_(2)[PW_(12)O_(40)]_n·x H_(2)O (n=1.5,x=6 for 1,n=1,x=12 for 2;and H_(3)pidc=2-(3-pyridinyl)-1H-imidazole-4,5-dicarboxylic acid),were consciously manufacture and employed for heterogeneously catalyzed sulfide-sulfoxide transformation.Structural analysis shows that 1 and 2 exhibit similar 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 being 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.

Enhancing oxidative desulfurization of polyoxometalate by integrating with a self-reductive framework

With the strict control of sulfur content in fuels,oxidative desulfurization(ODS),a promising desulphurization technology,needs to be continuously developed.In this study,we integrated multiple approaches(fabricating a porous structure,increasing phosphomolybdic acid(PMo)loading,improving amphiphilicity,and enhancing the intrinsic activity of PMo using a reductive framework)into PAF-54 carriers to improve ODS catalytic ability.The catalytic performance suggested that PAF-54 was not simply used as a carrier for PMo by physical integration.During the binding process,electron transfer between PAF-54 and PMo formed Mo^(5+)with superior catalytic activity.Owing to the presence of PAF-54,the catalytic activity of PMo as the active component qualitatively improved to achieve rapid and efficient desulfurization.More importantly,we found that other nitrogen-rich porous organic polymers can also reduce some of Mo^(6+)in PMo during loading,and its formation mechanism was investigated.This work provides a feasible strategy for designing highly efficient DOS catalysts.