Transition-metal substituted Keggin-type polyoxometalates(POMs)are of great interest for applications in biomedicine,material science,and catalysis.The synthesis of transition metal-substituted Keggin-type polytungsta...Transition-metal substituted Keggin-type polyoxometalates(POMs)are of great interest for applications in biomedicine,material science,and catalysis.The synthesis of transition metal-substituted Keggin-type polytungstates via the formation of a lacunary structure is well established,in contrast this approach is so far unexplored for Keggin-type polymolybdates.This is because the prevailing doctrine assumes that the lacunary Keggin phosphomolybdate[PMo_(9)O_(34)]^(9−)is too unstable and can only be stabilized with organic ligands such as pyridine in organic solvents.In this work,we present a reliable procedure for the synthesis of the lacunary compound[PMo_(9)O_(34)]^(9−)and its application in a novel in situ approach for the synthesis of different metal substituted POMs.The method is based on generating the lacunary species in situ,where the metal-substituted POMs are produced by adding another precursor compound.We employed this method to synthesize several new specific element-substituted POMs,which we present with comprehensive characterization.The interpretation of the analytical results was complemented by DFT calculations.For the separation of by-products from synthesis,we employed a novel membrane-based nanofiltration process,that enables superior separation of alkali salts from the POM solution resulting in>99%rejection of the POM components.展开更多
文摘Transition-metal substituted Keggin-type polyoxometalates(POMs)are of great interest for applications in biomedicine,material science,and catalysis.The synthesis of transition metal-substituted Keggin-type polytungstates via the formation of a lacunary structure is well established,in contrast this approach is so far unexplored for Keggin-type polymolybdates.This is because the prevailing doctrine assumes that the lacunary Keggin phosphomolybdate[PMo_(9)O_(34)]^(9−)is too unstable and can only be stabilized with organic ligands such as pyridine in organic solvents.In this work,we present a reliable procedure for the synthesis of the lacunary compound[PMo_(9)O_(34)]^(9−)and its application in a novel in situ approach for the synthesis of different metal substituted POMs.The method is based on generating the lacunary species in situ,where the metal-substituted POMs are produced by adding another precursor compound.We employed this method to synthesize several new specific element-substituted POMs,which we present with comprehensive characterization.The interpretation of the analytical results was complemented by DFT calculations.For the separation of by-products from synthesis,we employed a novel membrane-based nanofiltration process,that enables superior separation of alkali salts from the POM solution resulting in>99%rejection of the POM components.
