Chromate‐Mediated One‐Step Quantitative Transformation of PW₁₂ into P₂W₂₀ Polyoxometalates

Abstract

Polyoxometalates have been at the frontiers of science since the discovery of Keggin-type polyoxometalates (POMs) about a century ago. Today these polyoxometalates are still of major scientific interest, not only due to their wide range of applications [1][2][3][4][5][6][7][8][9][10][11][12] in analytical chemistry, in life sciences, as homo-and heterogeneous catalysts, as essential building blocks for the design of photoactive complexes, and hybrid organic/inorganic materials, but also from purely synthetic chemistry and structural points of view. [13,14] A review of patent applications [2] and commercial realizations reveals the popularity of Keggin-type POMs, H 8-x XM 12 O 40 3-[with X = Si 4+ or P 5+ , x = 4 (Si) or 5 (P), M = Mo 6+ or W 6+ ] and their salts due to their wellestablished fundamental chemistry, [15] easy synthesis and commercial availability. Polyoxometalate science and technology gains further momentum each time a new type of POM becomes easily accessible. In this work it has been demonstrated that the presence of potassium chromate enables the quantitative conversion of H 3 PW 12 O 40 crystals into K 13 [KP 2 W 20 O 72 ]·24H 2 O in alkaline aqueous medium. This new convenient room-temperature synthesis procedure makes K 13 [KP 2 W 20 O 72 ]·24H 2 O crystals readily accessible [a

Design and Synthesis of Reusable Nanoparticles for Reversible Chemisorption of Hexavalent Chromium Anions from Aqueous Media and Catalysis

“…e chromate anions are recovered by adding stoichiometric amounts of KOH solution to the Cr(VI) solution to yield potassium chromate powder after solvent evaporation (Figure 15). is is in agreement with the proposed reaction pathway of PW 10 Cr 2 (aq) species [22]. Most importantly, we are able to isolate this intermediate species.…”

“…Polyoxometalates (POMs) are a class of discrete anionic metal oxides of groups 5 and 6 and POMs exhibit attractive properties such as thermal and oxidative stability, remarkable electronic and magnetic properties, and Brønsted acidity, which result in intriguing applications ranging from medicine, catalysis to material science [18][19][20][21]. Recently, it was reported that the slow addition of H 3 PW 12 O 40 to an aqueous solution of K 2 CrO 4 at room temperature (pH � 6.6 ± 0.2) led to the formation of the final product K 14 [P 2 W 20 O 72 ]•24H 2 O (denoted as P 2 W 20 ) [22]. It was proposed that a Cr(VI)-stabilized [PW 10 O 36 (CrO 4 ) 2 ] 9− intermediate was formed, which played a significant role in the formation of the P 2 W 20 cluster.…”

Observing Assembly of Complex Inorganic Materials from Polyoxometalate Building Blocks

“…Moreover, the ion-association, hydrolysis, and condensation reactions that lead to self-assembly of clusters into materials are at the heart of virtually all synthetic and natural aqueous inorganic processes. − Thus observing these processes directly in solution by methods such as small-angle X-ray scattering (SAXS) can provide valuable insight into fundamental aqueous ion behaviors that control crystallization, dissolution, transport, ion-exchange, and adsorption and desorption at interfaces. Yet the inorganic scientific community is only beginning to use this technique to full advantage. ,− …”