Recent advances in polyoxometalates acid-catalyzed organic reactions

Polyoxometalates(POMs)have conducive properties such as controlled Bronsted and Lewis acidity,high thermal stability,nontoxic nature,tunable solubility,and less corrosiveness.POMs have been extensively applied in catalytic organic reactions and have an exciting prospect for industrial applications.This review summarized recent progress in the application of POMs as acid catalysts for various organic reactions including C-C bond formation,C-N bond formation,C-O bond formation,heterocyclic synthesis reactions,cyanosilylation and hydrolysis reactions.Various POMs catalysts including heteropoly acids(HPAs)and cationic functionalized HPAs with Bronsted acidity,HPAs supported on non-precious metal support with Bronsted acidity(or both Bronsted and Lewis acidity),transition metal substituted POMs with Lewis acidity were applied in above reactions.This review attempts to provide up-to-date information about POMs acid-catalyzed organic reactions and propose future prospects.

Design and synthesis of hybrid solids based on the tetravanadate core toward improved catalytic properties

Five inorganic-organic hybrid vanadates based on tetravanadate cores, transition metals and N-donor ligands have been designed and synthesized under hydrothermal conditions, namely, [Zn（elM）312V4O12 （1）, [Zn（plM）3]2V4O12.H2O （2）, [Zn（iplM）3]2V4O12 （3）, [Co（eIM）3]2V4O12.H2o （4）, [Cu（eIM）2（H20）]2V4O12 （5） （eIM = 1-ethylimidazole, plM = 1-propylimidazole, ipIM = isopropylimidazole）. All compounds were fully characterized by single-crystal XRD, powder XRD, elemental analysis, TGA, and FT-IR spectroscopy. The hybrid zinc vanadates （1-3） and cobalt vanadate （4） exhibit interesting 2D folded structures and the hybrid copper vanadate （5） presents a 1D chain configuration. All compounds can catalyze olefin epoxidation reactions when using TBHP （TBHP = tert-butyl hydroperoxide） as an oxidant in acetonitrile. The introduction of transition metal ions into tetravanadate cores not only improved the catalytic activity but also fulfilled the heterogeneous catalytic behavior. 1-5 all exhibit extraordinary efficiency in converting olefins to the corresponding epoxides with high conversion and selectivity （particularly, cony. up to 97.1%, sele. up to 100% for 1 ）. Leaching test was also carried out to prove the heterogeneous behavior.

Supramolecular assembly of Keggin polyoxomolybdate and 2,2'-bipyridine generated in situ from a decarboxylation coupling reaction

An assembly of Keggin polyoxomolybdate and organic substrate （Hbipy）3[PM01204o] （1, bipy = 2,2＇- bipyridine） was synthesized and characterized by elemental analysis, infrared spectrum, and single- crystal X-ray analysis. The ligand bipy of compound 1 was generated by a decarboxylation coupling reaction of H2pdc （H2pdc = pyridine-2,6-dicarboxylic acid） in situ under hydrothermal reaction conditions and the control experiments illustrate that La（NO3）3 or Ce（NO3）3, which does not appear in the final structure, is necessary for the decarboxylation coupling reaction. Moreover, compound 1 displays strong photoluminescence property in the solid state at room temperature.