Study on the incorporation of various elements into the Keggin lacunary-type phosphomolybdate [PMo₉O₃₄]⁹⁻ and subsequent purification of the polyoxometalates by nanofiltration

Abstract

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...

Heteroelements in polyoxometalates: a study on the influence of different group 15 elements on polyoxometalate formation

“…The distance is comparable to the O–Na distance between a Keggin-type anion and its Na + counterions (2.986 Å), which we observed in a recently published crystal structure of Na 6 [PV 3 Mo 9 O 40 ] (deposition number 2205007). 21…”

“…On each metal atom is one terminally coordinated oxo ligand with partial double bond character as indicated by a shortened bond length. 5,12,19–21 The stabilizing effect caused by P( v ) in the Keggin-type POMs goes so far that a substitution of the addenda framework metal with other elements such as vanadium( v ), niobium( v ), iron( iii ), manganese( ii ), cobalt( ii ) etc . is possible without compromising the structural integrity of the cluster.…”

Catalytic Valorization of Humins by Selective Oxidation Using Transition-Metal-Substituted Keggin-Type Polyoxometalate Catalysts

“…Those investigations will lead to a more efficient and selective process for the valorization of humins and thus facilitating separation processes. Previous studies have shown that nanofiltration is a promising downstream process for homogeneously catalyzed reactions using POMs. ,, The use of nanofiltration as a downstream process for the oxidative valorization of humins could also be an integral part of further investigations. Nevertheless, the present comprehensive study provides important insights into structure–activity–selectivity relationships of various functional groups and bonding types as well as the tailoring of POM catalysts, thereby providing a promising basis for further investigations.…”

“…The incorporation of niobium (Nb) into the POM catalyst was achieved by a novel synthesis approach using a lacunary Keggin-type structure according to the literature . According to this procedure, sodium molybdate dihydrate (9 equiv) and disodium hydrogen phosphate (1 equiv) were dissolved in water.…”

“…Sodium molybdate dihydrate (2 equiv) was added. The yellow solution was refluxed for 2 h. After cooling to room temperature, the solution was filtered and purified according to our previously published nanofiltration approach . All synthesized catalysts used were extensively characterized, as described below ( vide infra , catalyst characterization).…”